PHOTO

Shin Yoshizawa
Section
Graduate School of Engineering
Job title
Professor
Degree

  • 博士（工学）（東京大学）

  • 修士（工学）（東京大学）

Research History 7

  • 2021/10 - Present
    Tohoku University　Graduate School of Engineering, Department of Communications Engineering　Professor

  • 2013/05 - 2021/09
    Tohoku University　Graduate School of Engineering, Department of Communications Engineering

  • 2012/04 - 2013/04
    Tohoku University　Graduate School of Engineering, Department of Communications Engineering

  • 2007/05 - 2012/03
    Tohoku University　Graduate School of Engineering, Department of Electrical and Communication Engineering

  • 2007/04 - 2007/04
    理化学研究所　日本学術振興会特別研究員（PD）

  • 2006/04 - 2007/03
    東京大学大学院工学系研究科　日本学術振興会特別研究員（PD）

  • 2002/04 - 2003/03
    日本電気株式会社

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Education 5

  • The University of Tokyo　Graduate School, Division of Engineering

    2003/10 - 2006/03

  • The University of Tokyo　The Graduate School of Engineering

    2003/04 - 2003/09

  • The University of Tokyo　The Graduate School of Engineering　Department of Mechanical Engineering

    2000/04 - 2002/03

  • The University of Tokyo　Faculty of Engineering　産業機械工学科

    1998/04 - 2000/03

  • The University of Tokyo　College of Arts and Sciences

    1996/04 - 1998/03

Professional Memberships 5

  • ACOUSTICAL SOCIETY OF JAPAN

  • IEEE

  • 電子情報通信学会

  • The Japan Society of Ultrasonics in Medicine

  • The Japan Society of Mechanical Engineers

Research Interests 4

  • ultrasound treatment

  • HIFU

  • cavitaiton

  • microbubble

Research Areas 3

  • Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Fluid engineering /

  • Life sciences / Biomaterials /

  • Life sciences / Biomedical engineering /

Awards 6

  1. Best paper award

    2023/05　Displacement detection with sub-pixel accuracy and high spatial resolution using deep learning

  2. Symposium on Ultrasonic Electronics Best Paper Award

    2021/10　Comparison between thermal strain and acoustic radiation force imaging methods for estimation of heat source distribution of high-intensity focused ultrasound

  3. Symposium on Ultrasonic Electronics Best Paper Award

    2018/10　Singular value decomposition of received ultrasound signal to separate tissue, blood flow, and cavitation signals

  4. Symposium on Ultrasonic Electronics Best Paper Award

    2016/11　Quantitative measurement of ultrasound pressure field by optical phase contrast method and acoustic holography

  5. 日本超音波医学会第15回奨励賞

    2014/05/10　一般社団法人日本超音波医学会

  6. 2006年度 日本機械学会賞（論文賞）

    2007/04/06　日本機械学会

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Papers 98

  1. Basic study on a filtering method for selectively extracting cavitation bubble region in ultrasound imaging by triplet pulse sequence

    Shota Kuji, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　62　(SJ)　2023/07/01

    DOI： 10.35848/1347-4065/acbe03 　

    ISSN：0021-4922

    eISSN：1347-4065

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    In the high-intensity focused ultrasound treatment enhanced by cavitation bubbles, monitoring cavitation bubbles is important to ensure the safety and efficacy of the treatment. In previous studies, a triplet pulse sequence (3P) was proposed to extract nonlinear echoes from bubbles. However, it was difficult to distinguish between the bubble component and the component from strong scatterers. In this study, in addition to 3P method, a filtering method to effectively extract cavitation bubble regions was proposed, and its effectiveness was experimentally examined. The proposed method extracts cavitation bubbles by setting a threshold value for the ratio of the amplitude from a 3P image to that from a 1P image (3P/1P). Under the conditions in this study (imaging frequency:2.45 MHz), the proposed can filter out the regions without bubbles by performing 3P/1P with the average values in the region of interest (2 × 2 mm2) and setting a threshold of −20 dB.

  2. Development of efficient method of generating reactive oxygen species by expanding cavitation region using ultrasound focus scanning in the direction of ultrasound propagation

    Shotaro Miyake, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　62　(SJ)　2023/07/01

    DOI： 10.35848/1347-4065/accaf0 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Sonodynamic therapy is a minimally invasive high-intensity focused ultrasound (HIFU) based therapy that combines a sonosensitizer and reactive oxygen species (ROS), which are produced by acoustic cavitation. In this paper, we experimentally examined the effectiveness of a proposed method of scanning the ultrasound focus in the direction of HIFU propagation for continuously generating cavitation clouds to expand the region of ROS generation and increase the amount of ROS. First, the continuous generation of cavitation bubbles was observed using a high-speed camera, and it was confirmed that bubbles could be generated even with a short-duration HIFU, which is difficult to generate bubbles by itself. Subsequently, we evaluated the area and amount of ROS generation by imaging sonochemiluminescence. Comparing the irradiation at 1 point with that at 7 points, the amount of ROS per acoustic energy increased by about 1.5 times, suggesting that it is an efficient method for ROS generation.

  3. A study on correction method of total acoustic power in presence of shielding in focused ultrasound treatment using acoustic radiation force imaging

    Erika Numahata, Shin Yoshizawa, Shin Ichiro Umemura, Takuro Ishii, Yoshifumi Saijo

    Japanese Journal of Applied Physics　62　2023/07/01

    Publisher: IOP Publishing

    DOI： 10.35848/1347-4065/acc595 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Abstract High-intensity focused ultrasound (HIFU) therapy is a noninvasive treatment for cancer. Prediction of the HIFU treatment region in advance by ultrasound imaging is important for the efficacy and safety of the treatment. Acoustic radiation force (ARF) imaging has been shown to be useful in estimating the heat distribution caused by HIFU. In this study, we investigated the effect of shielding on the estimated heat distribution when the propagation of HIFU is partially shielded by an object simulating ribs, imitating an actual clinical situation, and examined the correction method of HIFU output power using ARF imaging to obtain tissue coagulation equivalent to that without shielding. As a result, it was suggested that even with partial acoustic shielding, when the HIFU output power is adjusted so that the displacement induced by ARF is equal to that without shielding, almost the same coagulated region can be obtained as in the unshielded case.

  4. Quantitative analysis of heat-source estimation of high-intensity focused ultrasound using thermal strain imaging

    Nozomi Obara, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　61　(SG)　2022/07/01

    DOI： 10.35848/1347-4065/ac5d15 　

    ISSN：0021-4922

    eISSN：1347-4065

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    For the clinical application of high-intensity focused ultrasound (HIFU), improvement in monitoring and guidance methods is necessary to enhance the treatment accuracy. Among the ultrasonic imaging techniques, thermal strain imaging has a potential to estimate temperature change based on the linear relationship between the thermally induced strain and temperature change via a tissue-dependent coefficient. In this study, the coefficient was experimentally measured and the temperature rise induced by the HIFU irradiation was estimated based on the measured coefficient in a tissue mimicking material phantom. The temperature rise estimated using the measured coefficient and that simulated based on a bioheat transfer equation showed a good agreement when the spatial averaged effect in the elevational direction was considered. The exponential decay time constants also agreed well within the range of measurement.

  5. 光音響・高周波超音波 東北大学における光音響/高周波超音波イメージング

    西條 芳文, 新楯 諒, 鈴木 陸, 石井 琢郎, 荒川 元孝, 梅村 晋一郎, 吉澤 晋, 長岡 亮, 小林 和人, 根本 隆治

    超音波医学　49　(Suppl.)　S522-S522　2022/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  6. Displacement detection with sub-pixel accuracy and high spatial resolution using deep learning

    Mariko Yamamoto, Shin Yoshizawa

    Journal of Medical Ultrasonics　49　(1)　3-15　2022/01

    DOI： 10.1007/s10396-021-01162-7 　

    ISSN：1346-4523

    eISSN：1613-2254

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    Purpose: The purpose of this study was to detect two dimensional and sub-pixel displacement with high spatial resolution using an ultrasonic diagnostic apparatus. Conventional displacement detection methods assume neighborhood uniformity and cannot achieve both high spatial resolution and sub-pixel displacement detection. Methods: A deep-learning network that utilizes ultrasound images and output displacement distribution was developed. The network structure was constructed by modifying FlowNet2, a widely used network for optical flow estimation, and a training dataset was developed using ultrasound image simulation. Detection accuracy and spatial resolution were evaluated via simulated ultrasound images, and the clinical usefulness was evaluated with ultrasound images of the liver exposed to high-intensity-focused ultrasound (HIFU). These results were compared to the Lucas–Kanade method, a conventional sub-pixel displacement detection method. Results: For a displacement within ± 40 µm (± 0.6 pixels), a pixel size of 67 µm, and signal noise of 1%, the accuracy was above 0.5 µm and 0.2 µm, the precision was above 0.4 µm and 0.3 µm, and the spatial resolution was 1.1 mm and 0.8 mm for the lateral and axial displacements, respectively. These improvements were also observed in the experimental data. Visualization of the lateral displacement distribution, which determines the edge of the treated lesion using HIFU, was also realized. Conclusion: Two-dimensional and sub-pixel displacement detection with high spatial resolution was realized using a deep-learning methodology. The proposed method enabled the monitoring of small and local tissue deformations induced by HIFU exposure.

  7. Effect of difference in shear modulus of biological tissue on heat source distribution of high-intensity focused ultrasound estimated by acoustic radiation force imaging

    Hiroki Yabata, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　60　2021/07

    DOI： 10.35848/1347-4065/abf4a7 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) is a novel noninvasive cancer treatment that is expected to be a potential alternative to conventional therapies. In the treatment, the accurate prediction of the ultrasonic heat source prior to therapeutic exposure is important for safety and efficacy. Acoustic radiation force imaging using a short HIFU burst has been proposed as a method for this prediction from the distribution of the tissue displacement. In this study, the effect of the difference in shear modulus on the estimation of the HIFU heat source was experimentally investigated by applying the imaging method to different biological tissues: chicken breast and chicken liver tissues. The result suggested that HIFU radiation force imaging has the potential to determine the HIFU power for appropriate treatment quantitatively from the displacement, even in different tissues with different shear moduli.

  8. Effects from correction of speed of sound in transmit and receive beamforming using focus beam

    Ryo Nagaoka, Shin Yoshizawa, Shin Ichiro Umemura, Hideyuki Hasegawa

    Japanese Journal of Applied Physics　60　(SD)　SDDE19-SDDE19　2021/07/01

    Publisher: IOP Publishing

    DOI： 10.35848/1347-4065/abf55b 　

    ISSN：0021-4922

    eISSN：1347-4065

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    In this study, focusing methods were investigated for generation of an ultrasonic beam with a uniform lateral width across the axial imaging field of view through numerical simulation using Field II. Also, the influence of the mismatch between the speed of sound (SoS) assumed in beamforming process and actual one was evaluated by wire and cyst phantom experiments. In the simulation, conventional, hybrid, and non-cylindrical focusing methods were evaluated based on the evaluation metrics, i.e. depth of field and lateral beam width. For the three focusing methods, the proper imaging parameters were determined based on the simulation results. In the phantom experiments, the lateral resolution was improved by correcting the SoS in receive beamforming. Additionally, the correction of the SoS in transmission focusing improved the uniformity of beam width and image contrast.

  9. Investigation of feasibility of noise suppression method for cavitation-enhanced high-intensity focused ultrasound treatment

    Ryo Takagi, Yoshihiko Koseki, Shin Yoshizawa, Shin ichiro Umemura

    Ultrasonics　114　2021/07

    DOI： 10.1016/j.ultras.2021.106394 　

    ISSN：0041-624X

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    In high-intensity focused ultrasound (HIFU) treatment, a method that monitors tissue changes while irradiating therapeutic ultrasound is needed to detect changes in the order of milliseconds due to thermal coagulation and the presence of cavitation bubbles. The new filtering method in which only the HIFU noise was reduced while the tissue signals remained intact was proposed in the conventional HIFU exposure in our preliminary study. However, HIFU was irradiated perpendicular to the direction of the imaging ultrasound in the preliminary experiment, which was believed to be impractical. This study investigated the efficacy of the proposed method a parallel setup, in which both HIFU and imaging beams have the same axis just as in a practical application. In addition, this filtering algorithm was applied to the “Trigger HIFU” sequence in which ultrasound-induced cavitation bubbles were generated in the HIFU focal region to enhance heating. In this setup and sequence, HIFU noise level was increased and the summation or difference tone induced by the interaction of HIFU waves with the imaging pulse has the potential to affect this proposed method. Ex-vivo experiments proved that the HIFU noise was selectively eliminated by the proposed filtering method in which chaotic acoustic signals were emitted by the cavitation bubbles at the HIFU focus. These results suggest that the proposed method was practically efficient for monitoring tissue changes in HIFU-induced cavitation bubbles.

  10. Effect of focal spot scanning method in agarose gel and chicken breast on heating efficiency in cavitation-enhanced ultrasonic heating

    Kohei Ueda, Sayaka Ito, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　60　2021/07

    DOI： 10.35848/1347-4065/abf2a8 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) treatment is a non-invasive method of cancer treatment. In a HIFU treatment, ultrasound is focused on a target tumor tissue leading to temperature rise that coagulates the tissue. The treatment has a problem of long treatment time because a tumor is usually larger than the focal spot of HIFU. To reduce the treatment time, cavitation bubbles can be used for accelerating ultrasonic heating. Additionally, the heat conducting away from a focal spot can be utilized by properly scanning the focus. In this study, three sequences of scanning the focus to form six foci were compared by observing cavitation bubbles and measuring temperature rise in an excised chicken breast tissue and an agarose gel as well as a thin slice of tissue sandwiched between agarose gels. The results showed that there were differences in the behavior of bubbles and the efficient sequence between the tissue and the gel.

  11. Comparison between thermal strain and acoustic radiation force imaging methods for estimation of heat source distribution of high-intensity focused ultrasound

    Nozomi Obara, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　60　(SD)　2021/07

    DOI： 10.35848/1347-4065/abef0a 　

    ISSN：0021-4922

    eISSN：1347-4065

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    In high-intensity focused ultrasound treatment, targeting its focal region prior to the thermal coagulation is required for the safety and efficacy of the treatment because the size and position of the thermally effective focal zone depend on the acoustic properties of the tissue. Acoustic radiation force impulse imaging can estimate the focal region from the displacement caused by ARF which stems from ultrasonic attenuation. Thermal strain (TS) imaging is another targeting method, which is based on temperature rise caused by tissue absorption. In this study, the TS imaging and temperature measurement by thermocouple were conducted for the same location, and a linear relationship between the TS and temperature rise was confirmed. In addition, the differences of the distribution depending upon the physical phenomena such as the thermo-acoustic lens effect and the effect of acoustic reflection were observed by comparing two imaging methods.

  12. Effect of ultrasonic intensity and intervals of ultrasonic exposure on efficiency of sonochemiluminescence in gel phantom for sonodynamic therapy

    Kenki Tsukahara, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　60　2021/07

    DOI： 10.35848/1347-4065/abf4a4 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Sonodynamic treatment (SDT) is one of the non-invasive modalities for cancer treatment. In SDT, ultrasound, reactive oxygen species (ROS) generated from cavitation bubbles, and a sonosensitizer are used in combination. In this study, high-intensity focused ultrasound (HIFU) was employed as ultrasound to generate and oscillate cavitation bubbles. When cavitation bubbles oscillate and collapse, the gas inside the bubble is extremely compressed and heated, inducing ROS generation. The disadvantage of SDT is a long treatment time because of its smallness of a treatment region by a shot of HIFU. To overcome this, the effect of the intensity and interval of HIFU for oscillating cavitation bubbles was investigated by using luminol sonochemiluminescence and high-speed imaging. The results showed that a HIFU exposure sequence with an interval of 300 ms and a burst-wave intensity of 0.25 kW cm-2 improve the energy efficiency of ROS generation.

  13. Analysis of tissue displacement induced by high-intensity focused ultrasound exposure for coagulation monitoring

    Mariko Yamamoto, Shin Yoshizawa

    Japanese Journal of Applied Physics　60　(4)　2021/04

    DOI： 10.35848/1347-4065/abeb4c 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Decorrelation between two ultrasound images has been investigated for real-time monitoring of lesion formation caused by high-intensity focused ultrasound (HIFU) exposure. However, the origin of the decorrelation remains unclear. In this study, the distributions of tissue displacement were obtained from numerical simulation and experimental data, and the latter was compared to the decorrelation map. The results show the possibility that decorrelation of ultrasonic signals can be explained by thermal expansion and apparent displacement caused by the temperature dependence of the speed of sound.

  14. Effects of intermittent duration of ultrasound exposure on temperature rise and behavior of cavitation bubbles in bubble-enhanced ultrasonic heating

    Sayaka Ito, Shin Ichiro Umernura, Shin Yoshizawa

    Acoustical Science and Technology　41　(6)　913-916　2020/11/01

    DOI： 10.1250/ast.41.913 　

    ISSN：1346-3969

    eISSN：1347-5177

  15. Effect of split-aperture transmission on cavitation bubbles and ultrasonic heating outside focal region in high-intensity focused ultrasound exposure

    Yui Tanaka, Shin Ichiro Urnernura, Shin Yoshizawa

    Acoustical Science and Technology　41　(6)　909-912　2020/11/01

    DOI： 10.1250/ast.41.909 　

    ISSN：1346-3969

    eISSN：1347-5177

  16. Experimental investigation of effect of ultrasonic duty cycle on generation of reactive oxygen species for highly efficient sonodynamic treatment Peer-reviewed

    Kenki Tsukahara, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　59　SKKE08　2020/07

    DOI： 10.35848/1347-4065/ab82a5 　

    ISSN：0021-4922

    eISSN：1347-4065

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    © 2020 The Japan Society of Applied Physics. Sonodynamic treatment (SDT) is a non-invasive treatment of cancer, combining ultrasound, reactive oxygen species (ROS), and sonosensitizer. When cavitation bubbles generated by ultrasound oscillate and collapse, ROS are generated due to the high temperature and high pressure inside the bubble. By generating cavitation bubbles in a target tissue, it can be treated by the cytotoxicity of ROS, which can be further enhanced by a sonosensitizer. In SDT, the small treatment region by a single shot of HIFU results in a long treatment time, which needs to be reduced by improving the efficiency of ROS generation. ROS can be visualized by the sonochemiluminescence of luminol. In this study, a polyacrylamide gel soaked with luminol solution is used as a target of ultrasonic exposure. The effect of the duty cycle of HIFU exposure on ROS generation was investigated by capturing sonochemiluminescent light emission, and high-speed photography of cavitation bubbles.

  17. Ultrasound imaging of cavitation using triplet pulse sequence in bubble-enhanced ultrasonic heating Peer-reviewed

    Ikumi Shiozaki, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　59　SKKE05　2020/07

    DOI： 10.35848/1347-4065/ab7fe5 　

    ISSN：0021-4922

    eISSN：1347-4065

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    © 2020 The Japan Society of Applied Physics. High-intensity focused ultrasound (HIFU) treatment enhanced by cavitation bubbles requires monitoring of the bubbles in the treatment region to ensure the efficacy and safety. In the intraoperative guidance by ultrasound, the bubbles in the treatment region are visualized by detecting nonlinear echoes from them. A triplet pulse sequence (3P) was developed in order to solve the disadvantage of the conventional method by which it is difficult to discriminate between the nonlinear echoes generated by the nonlinear oscillation of bubbles and those by the nonlinear propagation of ultrasound. In this study, we investigated the selectivity of cavitation bubbles in imaging by 3P in various HIFU exposure sequences to improve the efficacy and safety of cavitation-enhanced HIFU therapy. This study proved that the highest contrast could be obtained by 3P in most cases and that the combination of HIFU exposure and imaging sequences was important to obtain a high contrast image.

  18. Effect of shear wave propagation on estimation of heating distribution by high-intensity focused ultrasound using acoustic radiation force imaging Peer-reviewed

    Hiroki Yabata, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　59　SKKE19　2020/07

    DOI： 10.35848/1347-4065/ab8be4 　

    ISSN：0021-4922

    eISSN：1347-4065

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    © 2020 The Japan Society of Applied Physics. In a high-intensity focused ultrasound (HIFU) treatment, to predict a HIFU heat source is important for the safety and efficiency. Acoustic radiation force impulse imaging using a HIFU burst is known as a method for the prediction from the distribution of the tissue displacement in a homogeneous tissue. However, the distribution induced by HIFU radiation force expands as the shear wave propagates. In this study, the effect of the shear wave propagation on the estimation of the heat source distribution was investigated by changing the burst duration and intensity of HIFU. The results showed that a shorter HIFU burst provided the higher accuracy of the prediction, improving the spatial resolution. It is concluded that the estimation method has the potential to estimate in a wide range of HIFU energy and requires one to obtain the distribution of displacements immediately after the start of HIFU burst exposure.

  19. Ultrasound Sub-pixel Motion-tracking Method with Out-of-plane Motion Detection for Precise Vascular Imaging Peer-reviewed

    Hideki Yoshikawa, Taku Yamamoto, Tomohiko Tanaka, Ken ichi Kawabata, Shin Yoshizawa, Shin ichiro Umemura

    Ultrasound in Medicine and Biology　46　(3)　782-795　2020/03

    DOI： 10.1016/j.ultrasmedbio.2019.11.005 　

    ISSN：0301-5629

    eISSN：1879-291X

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    © 2019 The Authors Ultrasound vascularity imaging provides important information for differential diagnosis of tumors. Peak-hold (PH) is a useful technique for precisely imaging small vessels by selecting a maximum brightness in each pixel through the frames obtained sequentially. To use PH successfully one needs motion compensation to reduce image blur, but out-of-plane motion cannot be avoided. To address this problem, we developed a sub-pixel motion-tracking method with out-of-plane motion detection (OPMD). It is a combination of the sum of the absolute differences (SAD) method and the Kanade-Lucas-Tomasi method and can be accurately applied to various motions. The value from OPMD (γ) is defined as a statistical value obtained from the distribution of residual values in the SAD procedure with the obtained frames. The value is ideally 0, and the frames having large γ are removed from the PH procedure. The accuracy of the proposed tracking method was found by a simulation study to be approximately 20 μm. We also found, through a phantom experiment, that the value of γ sensitively increased enough to detect out-of-plane motion. Most important, γ begins to increase before tracking errors occur. This suggests that OPMD can be used to predict tracking errors and effectively remove frames from the PH procedure. An in vivo experiment with a rabbit showed that the PH image obtained with motion tracking clearly revealed peripheral vessels that were blurred in the PH image obtained without motion tracking. We also found that the image quality becomes better when OPMD was used to remove frames including out-of-plane motion.

  20. Treatment of twin-reversed arterial perfusion sequence using high-intensity focused ultrasound

    K. Seo, K. Ichizuka, T. Okai, S. Dohi, M. Nakamura, J. Hasegawa, R. Matsuoka, S. Yoshizawa, S. I. Umemura, M. Nagatsuka, A. Sekizawa

    Ultrasound in Obstetrics and Gynecology　54　128-134　2019/07/01

    DOI： 10.1002/uog.20101 　

    ISSN：0960-7692

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    Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd. We describe our experience of high-intensity focused ultrasound (HIFU) for fetal therapy in twin-reversed arterial perfusion (TRAP) sequence. Six pregnant women underwent HIFU therapy, five before 16 weeks and one at 26 weeks. Two types of HIFU system were used: the first-generation system, which comprised a biaxial transducer and continuous exposure pattern, and the second-generation system, which comprised a coaxial transducer and sequential exposure pattern. The first-generation apparatus was used in four cases and the second-generation apparatus was used in two. In three cases, occlusion of the blood vessels mediating flow to the acardiac twin was achieved by HIFU. Two cases experienced intrauterine fetal death despite vessel occlusion. The total survival rate of pump fetuses 2 years after HIFU was 67% and the efficiency rate (the proportion of cases with occlusion or reduced blood flow on ultrasound after HIFU) was 83%. After more than 2 years of follow-up, the surviving infants had no severe clinical complications and no postnatal developmental problems. There was no significant difference in survival rate compared with TRAP cases managed expectantly. Given that complete occlusion of the blood vessels was not achieved in half of the cases, we could not show that HIFU therapy is superior to other treatments. However, HIFU can reduce the cardiac load of the pump fetus and, as it does not require uterine puncture for fetal therapy, there were no fatal complications, such as bleeding, rupture of membranes or infection. Thus, HIFU therapy may represent a less-invasive treatment for TRAP sequence in early pregnancy. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

  21. Sonodynamic Therapy: Advances and Challenges in Clinical Translation

    Maxime Lafond, Shin Yoshizawa, Shin ichiro Umemura

    Journal of Ultrasound in Medicine　38　567-580　2019/03/01

    DOI： 10.1002/jum.14733 　

    ISSN：0278-4297

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    © 2018 by the American Institute of Ultrasound in Medicine Sonodynamic therapy (SDT) consists of the synergetic interaction between ultrasound and a chemical agent. In SDT, the cytotoxicity is triggered by ultrasonic stimuli, notably through cavitation. The unique features of SDT are relevant in the clinical context more than ever: the need for efficacy, accuracy, and safety while being noninvasive and preserving the patient's quality of life. However, despite the promising results of this technique, only a few clinical reports describe the use of SDT. The objective of this article is to provide an extensive overview of the clinical and preclinical research conducted in vivo on SDT, to identify the limitations, and to detail the developed strategies to overcome them.

  22. Blood flow imaging using singular value decomposition filter during high-intensity focused ultrasound exposure Peer-reviewed

    Hayato Ikeda, Shin Yoshizawa, Moe Maeda, Shin Ichiro Umemura, Yoshifumi Saijo

    Japanese Journal of Applied Physics　58　SGGE15　2019

    DOI： 10.7567/1347-4065/ab1a2e 　

    ISSN：0021-4922

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    © 2019 The Japan Society of Applied Physics. High-intensity focused ultrasound (HIFU) is a minimally invasive treatment modality to induce thermal coagulation. In clinical cases, noninvasive blood flow occlusion was successfully achieved by HIFU exposure. However, it is difficult to monitor the blood flow during HIFU exposure due to the interference of HIFU noise with RF echo signals. In this study, we proposed a novel filtering method for monitoring blood flow during HIFU exposure by combining an singular value decomposition (SVD) filter with the HIFU noise reduction method. The HIFU noise was reducted by subtracting the RF signals of passive imaging from the RF signals of active imaging while keeping the tissue and blood flow signals intact. After that, the blood flow signals were identified by employing the SVD filter, on the basis of the spatiotemporal characteristics and amplitudes of these signals. The results imply that the proposed filtering method is useful for monitoring of blood flow during HIFU exposure.

  23. Effect of inter-focal distance and interval time in focus scanning of high-intensity focused ultrasound on efficiency of reactive oxygen generation Peer-reviewed

    Daisaku Mashiko, Shin Ichiro Umemura, Shin Yoshizawa

    Japanese Journal of Applied Physics　58　SGGE04　2019

    DOI： 10.7567/1347-4065/ab0df6 　

    ISSN：0021-4922

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    © 2019 The Japan Society of Applied Physics. Sonodynamic treatment (SDT) is a non-invasive cancer treatment using ultrasound, reactive oxygen species (ROS) generated by acoustic cavitation bubbles, and sonodynamically active antitumor agents. When cavitation bubbles collapse, they generate ROS, which can attack cancer cells by their cytotoxicity. For SDT, both localization and efficiency of generating ROS are important. In this study, high-intensity focused ultrasound (HIFU) was employed for localization and "Trigger HIFU" sequence was further employed for generating cavitation and ROS efficiently even under the progressive wave condition. A polyacrylamide gel containing luminol was employed to visualize the region of ROS generation by utilizing sonochemiluminescence of luminol. Focus scanning methods were thereby tested to further improve the ROS generation efficiency. In focus scanning irradiation, the time interval considering the bubble lifetime and the inter-focal distance considering the sidelobes were found to be important for efficient generation of ROS.

  24. Sonodynamic Therapy With Anticancer Micelles and High-Intensity Focused Ultrasound in Treatment of Canine Cancer. International-journal

    Yuki Horise, Masanori Maeda, Yoshiyuki Konishi, Jun Okamoto, Soko Ikuta, Yoshiharu Okamoto, Hiroshi Ishii, Shin Yoshizawa, Shinichiro Umemura, Tsuyoshi Ueyama, Satoshi Tamano, Atsushi Sofuni, Kazuhisa Takemae, Ken Masamune, Hiroshi Iseki, Nobuhiro Nishiyama, Kazunori Kataoka, Yoshihiro Muragaki

    Frontiers in pharmacology　10　545-545　2019

    DOI： 10.3389/fphar.2019.00545 　

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    Sonodynamic therapy (SDT) is a minimally invasive anticancer therapy involving a chemical sonosensitizer and high-intensity focused ultrasound (HIFU). SDT enables the reduction of drug dose and HIFU irradiation power compared to those of conventional monotherapies. In our previous study, mouse models of colon and pancreatic cancer were used to confirm the effectiveness of SDT vs. drug-only or HIFU-only therapy. To validate its usefulness, we performed a clinical trial of SDT using an anticancer micelle (NC-6300) and our HIFU system in four pet dogs with spontaneous tumors, including chondrosarcoma, osteosarcoma, hepatocellular cancer, and prostate cancer. The fact that no adverse events were observed, suggests the usefulness of SDT.

  25. Cavitation-threshold Determination and Rheological-parameters Estimation of Albumin-stabilized Nanobubbles Peer-reviewed

    Maxime Lafond, Akiko Watanabe, Shin Yoshizawa, Shin-Ichiro Umemura, Katsuro Tachibana

    Scientific Reports　8　(1)　7472　2018/12/01

    Publisher: Nature Publishing Group

    DOI： 10.1038/s41598-018-25913-8 　

    ISSN：2045-2322

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    Nanobubbles (NBs) are of high interest for ultrasound (US) imaging as contrast agents and therapy as cavitation nuclei. Because of their instability (Laplace pressure bubble catastrophe) and low sensitivity to US, reducing the size of commonly used microbubbles to submicron-size is not trivial. We introduce stabilized NBs in the 100-250-nm size range, manufactured by agitating human serum albumin and perfluoro-propane. These NBs were exposed to 3.34- and 5.39-MHz US, and their sensitivity to US was proven by detecting inertial cavitation. The cavitation-threshold information was used to run a numerical parametric study based on a modified Rayleigh-Plesset equation (with a Newtonian rheology model). The determined values of surface tension ranged from 0 N/m to 0.06 N/m. The corresponding values of dilatational viscosity ranged from 5.10-10 Ns/m to 1.10-9 Ns/m. These parameters were reported to be 0.6 N/m and 1.10-8 Ns/m for the reference microbubble contrast agent. This result suggests the possibility of using albumin as a stabilizer for the nanobubbles that could be maintained in circulation and presenting satisfying US sensitivity, even in the 3-5-MHz range.

  26. Singular value decomposition of received ultrasound signal to separate tissue, blood flow, and cavitation signals Peer-reviewed

    Ikeda Hayato, Nagaoka Ryo, Lafond Maxime, Yoshizawa Shin, Iwasaki Ryosuke, Maeda Moe, Umemura Shin-ichiro, Saijo Yoshifumi

    JAPANESE JOURNAL OF APPLIED PHYSICS　57　(7)　07LF04　2018/07

    DOI： 10.7567/JJAP.57.07LF04 　

    ISSN：0021-4922

  27. Basic study of improvement of axial resolution and suppression of time side lobe by phase-corrected Wiener filtering in photoacoustic tomography Peer-reviewed

    Nagaoka Ryo, Yoshizawa Shin, Umemura Shin-ichiro, Saijo Yoshifumi

    JAPANESE JOURNAL OF APPLIED PHYSICS　57　(7)　07LD11　2018/07

    DOI： 10.7567/JJAP.57.07LD11 　

    ISSN：0021-4922

  28. Selective detection of cavitation bubbles by triplet pulse sequence in high-intensity focused ultrasound treatment Peer-reviewed

    Iwasaki Ryosuke, Nagaoka Ryo, Yoshizawa Shin, Umemura Shin-ichiro

    JAPANESE JOURNAL OF APPLIED PHYSICS　57　(7)　07LF12　2018/07

    DOI： 10.7567/JJAP.57.07LF12 　

    ISSN：0021-4922

  29. Quantitative measurement of ultrasonic pressure field using combination of optical phase contrast and nonlinear acoustic holography methods Peer-reviewed

    Nakamura Takuya, Iwasaki Ryosuke, Yoshizawa Shin, Umemura Shin-ichiro

    JAPANESE JOURNAL OF APPLIED PHYSICS　57　(7)　07LB13　2018/07

    DOI： 10.7567/JJAP.57.07LB13 　

    ISSN：0021-4922

  30. Estimation of sonodynamic treatment region with sonochemiluminescence in gel phantom Peer-reviewed

    Mashiko Daisaku, Nishitaka Shinya, Iwasaki Ryosuke, Lafond Maxime, Yoshizawa Shin, Umemura Shin-ichiro

    JAPANESE JOURNAL OF APPLIED PHYSICS　57　(7)　07LF13　2018/07

    DOI： 10.7567/JJAP.57.07LF13 　

    ISSN：0021-4922

  31. Effect of annular focusing of ultrasound on rate of stone erosion using cavitation bubbles Peer-reviewed

    Yura Toshiya, Lafond Maxime, Yoshizawa Shin, Umemura Shin-ichiro

    JAPANESE JOURNAL OF APPLIED PHYSICS　57　(7)　07LB18　2018/07

    DOI： 10.7567/JJAP.57.07LB18 　

    ISSN：0021-4922

  32. Effect of scanning the focus on generating cavitation bubbles and reactive oxygen species by using trigger high-intensity focused ultrasound sequence Peer-reviewed

    Nishitaka Shinya, Mashiko Daisaku, Yoshizawa Shin, Umemura Shin-ichiro

    JAPANESE JOURNAL OF APPLIED PHYSICS　57　(7)　07LF25　2018/07

    DOI： 10.7567/JJAP.57.07LF25 　

    ISSN：0021-4922

  33. Visualization of murine lymph vessels using photoacoustic imaging with contrast agents Peer-reviewed

    Ryo Nagaoka, Takuya Tabata, Shin Yoshizawa, Shin-ichiro Umemura, Yoshifumi Saijo

    Photoacoustics　9　39-48　2018/03/01

    Publisher: Elsevier GmbH

    DOI： 10.1016/j.pacs.2018.01.001 　

    ISSN：2213-5979

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    Metastasis frequently occurs even in the early stage of breast cancer. This research studied the feasibility of using photoacoustic (PA) imaging for identifying metastasis in the lymph vessels of mice. The photoacoustic efficiency of various contrast agents was investigated, and the influence of scattered light was evaluated by using a lymph vessel phantom. The lymph vessels of mice were then visualized using the selected contrast agents: indocyanine green (ICG) and gold nanorods (AuNR). The attenuation of the PA imaging was −1.90 dB/mm, whereas that of the fluorescence imaging was −4.45 dB/mm. The results indicate the potential of identifying sentinel lymph nodes by using PA imaging with these contrast agents.

  34. SONODYNAMIC THERAPY BASED ON COMBINED USE OF LOW DOSE ADMINISTRATION OF EPIRUBICIN-INCORPORATING DRUG DELIVERY SYSTEM AND FOCUSED ULTRASOUND Peer-reviewed

    Masanori Maeda, Yoshihiro Muragaki, Jun Okamoto, Shin Yoshizawa, Nobutaka Abe, Hidekazu Nakamoto, Hiroshi Ishii, Kenichi Kawabata, Shinichiro Umemura, Nobuhiro Nishiyama, Kazunori Kataoka, Hiroshi Iseki

    ULTRASOUND IN MEDICINE AND BIOLOGY　43　(10)　2295-2301　2017/10

    Publisher: ELSEVIER SCIENCE INC

    DOI： 10.1016/j.ultrasmedbio.2017.06.003 　

    ISSN：0301-5629

    eISSN：1879-291X

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    Sonodynamic therapy (SDT) is currently considered as one of the promising minimally invasive treatment options for solid cancers. SDT is based on the combined use of a sonosensitizer drug and high-intensity focused ultrasound (HIFU) to produce cytotoxic reactive oxygen species (ROS) in and around neoplastic cells. Anthracycline drugs, including epirubicin (EPI), have been well known as effective sonosensitizers after interaction with focused ultrasound. Recently a new anticancer drug delivery system (DDS), NC-6300, has been developed that comprises EPI through an acid-labile hydrazone bond. In previous in vivo studies, NC-6300 showed basic drug safety and an excellent concentration property of EPI, and recently has been tested in clinical trials. For realizing minimally invasive cancer treatment, the present study demonstrated the effectiveness and feasibility of DDS-based SDT, which combined a small dose of NC-6300 and low energy of HIFU in mouse models of colon cancer and pancreatic cancer. (C) 2017 World Federation for Ultrasound in Medicine & Biology.

  35. Development of Real-Time 3-D Photoacoustic Imaging System Employing Spherically Curved Array Transducer Peer-reviewed

    Ryo Nagaoka, Takuya Tabata, Ryo Takagi, Shin Yoshizawa, Shin-Ichiro Umemura, Yoshifumi Saijo

    IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL　64　(8)　1223-1233　2017/08

    Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

    DOI： 10.1109/TUFFC.2017.2718030 　

    ISSN：0885-3010

    eISSN：1525-8955

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    Photoacoustic (PA) imaging is a promising imaging modality to visualize specific living tissues based on the light absorption coefficients without dyeing. In this paper, a real-time PA imaging system with a tunable laser was newly developed with an originally designed spherically curved array transducer. Five different series of experiments were conducted to validate the PA measurement system. The peak frequency of the transducer response was 17.7 MHz, and a volume-imaging rate of 3-D volume imaging was 10-20 volumes per second. The spatial resolution of imaging was 90-105 mu m along both the axial and lateral directions. The developed imaging system could measure a difference on an absorption coefficient of gold nanorods. Additionally, the PA imaging could visualize the in vivo microvasculatures of a human hand. This PA imaging system with higher spatial-temporal resolution and the tunable laser further should enhance our understanding of not only basic properties of the photo acoustics but also clinical applications.

  36. Simulation of optical propagation based on wave optics for phase retrieval in shadowgraph of ultrasonic field Peer-reviewed

    Hiroki Hanayama, Takuya Nakamura, Ryo Takagi, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　56　(7)　07JC13　2017/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.56.07JC13 　

    ISSN：0021-4922

    eISSN：1347-4065

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    A shadowgraph method has been proposed for fast and noninterference measurement of ultrasonic pressure field. However, special care has been needed in choosing an appropriate optical propagation length to obtain a satisfactory signal-to-noise ratio of the measurement while avoiding error from a geometrical optics approximation. In this study, we propose a new numerical method replacing the geometrical optics approximation to retrieve the optical phase for the measurement. Optical intensity distribution obtained from the numerical simulation of optical propagation based on the Huygens-Fresnel principle agreed well with the measurement at a relatively large optical propagation length at which the geometrical optics approximation failed. Optical phase retrieval from the simulated optical intensity distribution by the proposed method was then tested. The range of optical propagation for successful phase retrieval was extended a few times by the proposed method compared with the geometrical optics approximation. (C) 2017 The Japan Society of Applied Physics

  37. Prediction of thermal coagulation from the instantaneous strain distribution induced by high-intensity focused ultrasound Peer-reviewed

    Ryosuke Iwasaki, Ryo Takagi, Kentaro Tomiyasu, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　56　(7)　07JF23　2017/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.56.07JF23 　

    ISSN：0021-4922

    eISSN：1347-4065

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    The targeting of the ultrasound beam and the prediction of thermal lesion formation in advance are the requirements for monitoring high-intensity focused ultrasound (HIFU) treatment with safety and reproducibility. To visualize the HIFU focal zone, we utilized an acoustic radiation force impulse (ARFI) imaging-based method. After inducing displacements inside tissues with pulsed HIFU called the push pulse exposure, the distribution of axial displacements started expanding and moving. To acquire RF data immediately after and during the HIFU push pulse exposure to improve prediction accuracy, we attempted methods using extrapolation estimation and applying HIFU noise elimination. The distributions going back in the time domain from the end of push pulse exposure are in good agreement with tissue coagulation at the center. The results suggest that the proposed focal zone visualization employing pulsed HIFU entailing the high-speed ARFI imaging method is useful for the prediction of thermal coagulation in advance. (C) 2017 The Japan Society of Applied Physics

  38. Simultaneous observation of cavitation bubbles generated in biological tissue by high-speed optical and acoustic imaging methods Peer-reviewed

    Kai Suzuki, Ryosuke Iwasaki, Ryo Takagi, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　56　(7)　07JF27　2017/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.56.07JF27 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Acoustic cavitation bubbles are useful for enhancing the heating effect in high-intensity focused ultrasound (HIFU) treatment. Many studies were conducted to investigate the behavior of such bubbles in tissue-mimicking materials, such as a transparent gel phantom; however, the detailed behavior in tissue was still unclear owing to the difficulty in optical observation. In this study, a new biological phantom was developed to observe cavitation bubbles generated in an optically shallow area of tissue. Two imaging methods, high-speed photography using light scattering and highspeed ultrasonic imaging, were used for detecting the behavior of the bubbles simultaneously. The results agreed well with each other for the area of bubble formation and the temporal change in the region of bubbles, suggesting that both methods are useful for visualizing the bubbles. (C) 2017 The Japan Society of Applied Physics

  39. Basic study on ultrasonic monitoring using 1.5-dimensional ultrasound phased array for ultrasound-guided high-intensity focused ultrasound treatment Peer-reviewed

    Ryo Takagi, Ryosuke Iwasaki, Kentaro Tomiyasu, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　56　(7)　07JF22　2017/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.56.07JF22 　

    ISSN：0021-4922

    eISSN：1347-4065

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    We have been studying a real-time detection method for tissue changes induced by high-intensity focused ultrasound (HIFU) treatment using ultrasonic RF signals. It has been difficult to track the target region when the tissue to be treated deviates from the imaging plane along the elevation axis of the probe. In this study, a new 1.5-dimensional (1.5D) prototype phased array probe consisting of transducer elements along both the lateral and elevation axes was developed to track tissue motion along the elevation axis of the probe, and the elevational displacement range where the tracking is effective was investigated. The complex cross-correlation coefficient based on a block matching algorithm was applied to 2.5D volumetric RF images acquired by the 1.5D probe and the displacement vector along the elevation axis was calculated. From the results, it was found that the effective tracking range using this prototype probe was up to 3mm, about 3 times that of a conventional 1D imaging probe. The proposed 1.5D phased array probe has the potential to track target tissue with intrafractional motion. (C) 2017 The Japan Society of Applied Physics

  40. Multifunctional pulse generator for high-intensity focused ultrasound system Peer-reviewed

    Satoshi Tamano, Shin Yoshizawa, Shin-Ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　56　(7)　07JF21　2017/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.56.07JF21 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) can achieve high spatial resolution for the treatment of diseases. A major technical challenge in implementing a HIFU therapeutic system is to generate high-voltage high-current signals for effectively exciting a multichannel HIFU transducer at high efficiencies. In this paper, we present the development of a multifunctional multichannel generator/driver. The generator can produce a long burst as well as an extremely high-voltage short pulse of pseudosinusoidal waves (trigger HIFU) and second-harmonic superimposed waves for HIFU transmission. The transmission timing, waveform, and frequency can be controlled using a field-programmable gate array (FPGA) via a universal serial bus (USB) microcontroller. The hardware is implemented in a compact printed circuit board. The test results of trigger HIFU reveal that the power consumption and the temperature rise of metal-oxide semiconductor field-effect transistors were reduced by 19.9% and 38.2 degrees C, respectively, from the previous design. The highly flexible performance of the novel generator/ driver is demonstrated in the generation of second-harmonic superimposed waves, which is useful for cavitation-enhanced HIFU treatment, although the previous design exhibited difficulty in generating it. (C) 2017 The Japan Society of Applied Physics

  41. Control of treatment size in cavitation-enhanced high-intensity focused ultrasound using radio-frequency echo signals Peer-reviewed

    Kentaro Tomiyasu, Ryo Takagi, Ryosuke Iwasaki, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　56　(7)　07JF28　2017/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.56.07JF28 　

    ISSN：0021-4922

    eISSN：1347-4065

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    In high-intensity focused ultrasound (HIFU) treatment, controlling the ultrasound dose at each focal target spot is important because it is a problem that the length of the coagulated region in front of the focal point deviates owing to the differences in absorption in each focal target spot and attenuation in the intervening tissues. In this study, the detected changes in the power spectra of HIFU echoes were used by controlling the HIFU duration in the "trigger HIFU" sequence with the aim to increase coagulation size through the enhancement of the ultrasonic heating by the cavitation induced by the preceding extremely high intensity short "trigger" pulse. The result shows that this method can be used to detect boiling bubbles and the following generated cavitation bubbles at their early stage. By automatically stopping HIFU exposure immediately after detecting the bubbles, overheating was prevented and the deviation of the length of the coagulated region was reduced. (C) 2017 The Japan Society of Applied Physics

  42. Enhancement of High-Intensity Focused Ultrasound Heating by Short-Pulse Generated Cavitation Peer-reviewed

    Shin Yoshizawa, Ryo Takagi, Shin-ichiro Umemura

    APPLIED SCIENCES-BASEL　7　(3)　288　2017/03

    Publisher: MDPI AG

    DOI： 10.3390/app7030288 　

    ISSN：2076-3417

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    A target tissue can be thermally coagulated in high-intensity focused ultrasound (HIFU) treatment noninvasively. HIFU thermal treatments have been clinically applied to various solid tumors. One of the problems in HIFU treatments is a long treatment time. Acoustically driven microbubbles can accelerate the ultrasonic heating, resulting in the significant reduction of the treatment time. In this paper, a method named trigger HIFU exposure which employs cavitation microbubbles is introduced and its results are reviewed. A trigger HIFU sequence consists of high-intensity short pulses followed by moderate-intensity long bursts. Cavitation bubbles induced in a multiple focal regions by rapidly scanning the focus of high-intensity pulses enhanced the temperature increase significantly and produced a large coagulation region with high efficiency.

  43. Evaluation of Second-generation HIFU Systems: Less-invasive Fetal Therapy for TRAP Sequence Peer-reviewed

    SEO Kohei, YOSHIZAWA Shin, UMEMURA Shin-ichiro, SEKIZAWA Akihiko, ICHIZUKA Kiyotake, OKAI Takashi, NAKAMURA Masamitsu, HASEGAWA Jun-ichi, MATSUOKA Ryu, KITADAI Yuzo, SUMIE Masahiro, TSUKIMORI Kiyomi

    The Showa University Journal of Medical Sciences　29　(3)　241-251　2017

    Publisher: Showa University Society

    DOI： 10.15369/sujms.29.241 　

    ISSN：0915-6380

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    In this report, the second-generation high-intensity focused ultrasound （HIFU） systems were clinically evaluated for human fetal therapy in two cases of twin reversed arterial perfusion sequence. The HIFU systems comprised an improved lead zirconate-titanate transducer with an imaging phase array sector probe, a Sonachill cooling system, and three phases of HIFU exposure: a trigger pulse, a continuous heating wave, and an idle period to obtain images with the imaging probe set on the transducer. To evaluate skin surface temperature, a thermal camera was used. To evaluate vessel occlusions, blood flow was measured at fixed timings after exposures. Target vessel occlusion was achieved with HIFU in only one of the cases, but recanalization occurred the following day. Both cases were finally treated with radiofrequency ablation and one infant was successfully delivered without any complications. This case highlighted three advantages with the change to second-generation HIFU systems in human fetal therapy: the simplicity of maneuvers by reduced range of motion disturbance; the ability to observe in real time during the exposure; and a decrease in total ultrasonic output. Treatment interruption due to burns or complaints of heat sensation represented an obstruction to treatment completion. This remains an issue to be addressed in the future.

  44. Feasibility of real-time treatment feedback using novel filter for eliminating therapeutic ultrasound noise with high-speed ultrasonic imaging in ultrasound-guided high-intensity focused ultrasound treatment Peer-reviewed

    Ryo Takagi, Hayato Jimbo, Ryosuke Iwasaki, Kentaro Tomiyasu, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　55　(7)　07KC10　2016/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.55.07KC10 　

    ISSN：0021-4922

    eISSN：1347-4065

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    In the conventional ultrasonic monitoring of high-intensity focused ultrasound (HIFU) treatment, a significant interval between HIFU shots is required when monitoring target tissue to avoid interference between HIFU noise and RF echo signals. In our previous study, a new filtering method to eliminate only HIFU noise while maintaining tissue signals intact was proposed, and it was shown that the thermal coagulation could be detected during simultaneous HIFU irradiation through off-line processing. In this study, the filtering method and a real-time coagulation detection algorithm were implemented in an ultrasound imaging system, whose use for sequential exposure with multiple foci was demonstrated similarly to a commercial HIFU ablation system. The coagulation was automatically detected by the proposed method during real-time simultaneous HIFU irradiation, and the HIFU exposure time was controlled according to the changes in the tissue. The results imply that ultrasonic monitoring with the filtering and detection methods is useful for true real-time detection of changes in the tissue due to thermal coagulation during HIFU exposure. (C) 2016 The Japan Society of Applied Physics

  45. Improvement of high-voltage staircase drive circuit waveform for high-intensity therapeutic ultrasound Peer-reviewed

    Satoshi Tamano, Hayato Jimbo, Takashi Azuma, Shin Yoshizawa, Keisuke Fujiwara, Kazunori Itani, Shin-Ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　55　(7)　07KF17　2016/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.55.07KF17 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Recently, in the treatment of diseases such as cancer, noninvasive or low-invasive modality, such as high-intensity focused ultrasound (HIFU), has been put into practice as an alternative to open surgery. HIFU induces thermal ablation of the target tissue to be treated. To improve the efficiency of HIFU, we have proposed a "triggered-HIFU" technique, which uses the combination of a short-duration, high-voltage transmission and a long-duration, medium-voltage transmission. In this method, the transmission device must endure high peak voltage for the former and the high time-average power for the latter. The triggered-HIFU sequence requires electronic scanning of the HIFU focus to maximize its thermal efficiency. Therefore, the transmission device must drive an array transducer with the number of elements on the order of a hundred or more, which requires that each part of the device that drives each element must be compact. The purpose of this work is to propose and construct such a transmission device by improving the staircase drive circuit, which we previously proposed. The main point of improvement is that both N and P MOSFETs are provided for each staircase voltage level instead of only one of them. Compared with the previous ultrasonic transmission circuit, high-voltage spikes were significantly reduced, the power consumption was decreased by 26.7%, and the transmission circuit temperature rise was decreased by 14.5 degrees C in the triggered-HIFU heating mode. (C) 2016 The Japan Society of Applied Physics

  46. Study on heavy matching layer transducer towards producing second harmonics Peer-reviewed

    Zulfadhli Zaini, Masamizu Osuga, Hayato Jimbo, Jun Yasuda, Ryo Takagi, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　55　(7)　07KF15　2016/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.55.07KF15 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Cavitation bubbles are microbubbles which can be incepted by highly negative pressure. Producing such highly negative pressure exceeding the cavitation threshold is difficult to accomplish due to nonlinear propagation followed by focal phase shift. By superimposing the second harmonic to fundamental is a way to significantly reduce the problem. However, the conventional design for an air-backed transducer is not suitable to generate both the second harmonic and fundamental at the same time. In order to overcome this problem, we propose a high impedance matching layer approach. Furthermore, we also construct a study to foresee the impact by adjusting the thickness ratio towards fundamental and second harmonic. Numerical simulation and experimental measurement have shown that by using a high impedance matching layer, efficiently generation of both the second harmonic (2MHz) and fundamental (1MHz) at the same time is possible. Besides, by adjusting the thickness ratio between piezocomposite and heavy matching layer will influence the amplitude of acoustic power over squared of voltage of the fundamental and second harmonic. (C) 2016 The Japan Society of Applied Physics

  47. Monitoring of high-intensity focused ultrasound treatment by shear wave elastography induced by two-dimensional-array therapeutic transducer Peer-reviewed

    Ryosuke Iwasaki, Ryo Takagi, Ryo Nagaoka, Hayato Jimbo, Shin Yoshizawa, Yoshifumi Saijo, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　55　(7)　07KF05　2016/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.55.07KF05 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Shear wave elastography (SWE) is expected to be a noninvasive monitoring method of high-intensity focused ultrasound (HIFU) treatment. However, conventional SWE techniques encounter difficulty in inducing shear waves with adequate displacements in deep tissue. To observe tissue coagulation at the HIFU focal depth via SWE, in this study, we propose using a two-dimensional-array therapeutic transducer for not only HIFU exposure but also creating shear sources. The results show that the reconstructed shear wave velocity maps detected the coagulated regions as the area of increased propagation velocity even in deep tissue. This suggests that "HIFU-push" shear elastography is a promising solution for the purpose of coagulation monitoring in deep tissue, because push beams irradiated by the HIFU transducer can naturally reach as deep as the tissue to be coagulated by the same transducer. (C) 2016 The Japan Society of Applied Physics

  48. Quantitative measurement of ultrasound pressure field by optical phase contrast method and acoustic holography Peer-reviewed

    Seiji Oyama, Jun Yasuda, Hiroki Hanayama, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　55　(7)　07KB09　2016/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.55.07KB09 　

    ISSN：0021-4922

    eISSN：1347-4065

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    A fast and accurate measurement of an ultrasound field with various exposure sequences is necessary to ensure the efficacy and safety of various ultrasound applications in medicine. The most common method used to measure an ultrasound pressure field, that is, hydrophone scanning, requires a long scanning time and potentially disturbs the field. This may limit the efficiency of developing applications of ultrasound. In this study, an optical phase contrast method enabling fast and noninterfering measurements is proposed. In this method, the modulated phase of light caused by the focused ultrasound pressure field is measured. Then, a computed tomography (CT) algorithm used to quantitatively reconstruct a three-dimensional (3D) pressure field is applied. For a high-intensity focused ultrasound field, a new approach that combines the optical phase contrast method and acoustic holography was attempted. First, the optical measurement of focused ultrasound was rapidly performed over the field near a transducer. Second, the nonlinear propagation of the measured ultrasound was simulated. The result of the new approach agreed well with that of the measurement using a hydrophone and was improved from that of the phase contrast method alone with phase unwrapping. (C) 2016 The Japan Society of Applied Physics

  49. Acceleration of lithotripsy using cavitation bubbles induced by second-harmonic superimposition Peer-reviewed

    Masamizu Osuga, Jun Yasuda, Hayato Jimbo, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　55　(7)　07KF18　2016/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.55.07KF18 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Shock wave lithotripsy potentially produces residual stone fragments too large to pass through ureters and significant injury to the normal tissue surrounding the stone. Previous works have shown that the collapse of cavitation bubbles induced by high-intensity focused ultrasound can produce small stone fragments via cavitation erosion. However, the erosion rate is hypothesized to be reduced by ultrasound attenuation by excessively generated bubble clouds. If so, it is important to generate the bubbles only on the stone surface. The effects of peak-negative-enhanced (PNE) and peak-positive-enhanced (PPE) waves obtained by second-harmonic superimposition were investigated to control cavitation bubbles. With the PNE waves, the bubbles were generated only on the stone surface and the maximum erosion rate was 232 +/- 32 mg/min. All the fragments were smaller than 2 mm, which makes them pass through ureters naturally. The proposed method shows the potential to significantly improve the speed of lithotripsy. (C) 2016 The Japan Society of Applied Physics

  50. Study on cavitation behavior during high-intensity focused ultrasound exposure by using optical and ultrasonic imaging Peer-reviewed

    Kei Taguchi, Ryo Takagi, Jun Yasuda, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　55　(7)　07KF22　2016/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.55.07KF22 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Cavitation bubbles are known to enhance the heating effect of high-intensity focused ultrasound (HIFU). In our previous study, the use of a "triggered HIFU" sequence consisting of a high-intensity pulse and a relatively low-intensity burst was proposed as an effective method to utilize the effect of cavitation bubbles. However, the duration of each component in the sequence has not been optimized. In this study, optical imaging was carried out to observe the behavior of cavitation bubbles in a gel phantom during the triggered HIFU exposure. Ultrasound imaging using the pulse inversion method was also conducted to detect the behavior of the bubbles. The results suggest that the oscillation of cavitation bubbles become inactive as the duration of HIFU burst exposure increases to the order of 10ms. It was also suggested that ultrasonic imaging has potential use for detecting a change in the oscillation of cavitation bubbles for optimizing a triggered HIFU sequence. (C) 2016 The Japan Society of Applied Physics

  51. Advantage of annular focus generation by sector-vortex array in cavitation-enhanced high-intensity focused ultrasound treatment Peer-reviewed

    Hayato Jimbo, Ryo Takagi, Kei Taguchi, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　55　(7)　07KF19　2016/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.55.07KF19 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) is a noninvasive method for cancer treatment. One of the disadvantages of this method is that it has a long total treatment time because of the smallness of the treatment volume by a single exposure. To solve this problem, we have proposed a method of cavitation-enhanced heating, which utilized the heat generated by oscillating the cavitation bubbles, in combination with the method of lateral enlargement of a HIFU focal zone to minimize the surface volume ratio. In a previous study, focal spot scanning at multiple points was employed for the enlargement. This method involves nonlinear propagation and absorption due to the high spatial-peak temporal-peak (SPTP) intensity in addition to the cavitation-enhanced heating. However, it is difficult to predict the size and position of the coagulation volume because they are significantly affected by the nonlinear parameters of the tissue. In this study, a sector vortex method was employed to directly synthesize an annular focal pattern. Since this method can keep the SPTP intensity at a manageably low level, nonlinear propagation and absorption can be minimized. Experimental results demonstrate that the coagulation was generated only in the region where both the cavitation cloud and the heating ultrasound were matched. The proposed method will make the cavitation-enhanced HIFU treatment more accurate and predictable. (C) 2016 The Japan Society of Applied Physics

  52. Efficient generation of cavitation bubbles and reactive oxygen species using triggered high-intensity focused ultrasound sequence for sonodynamic treatment Peer-reviewed

    Jun Yasuda, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　55　(7)　07KF24　2016/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.55.07KF24 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Sonodynamic treatment is a method of treating cancer using reactive oxygen species (ROS) generated by cavitation bubbles in collaboration with a sonosensitizer at a target tissue. In this treatment method, both localized ROS generation and ROS generation with high efficiency are important. In this study, a triggered high-intensity focused ultrasound (HIFU) sequence, which consists of a short, extremely high intensity pulse immediately followed by a long, moderate-intensity burst, was employed for the efficient generation of ROS. In experiments, a solution sealed in a chamber was exposed to a triggered HIFU sequence. Then, the distribution of generated ROS was observed by the luminol reaction, and the amount of generated ROS was quantified using KI method. As a result, the localized ROS generation was demonstrated by light emission from the luminol reaction. Moreover, it was demonstrated that the triggered HIFU sequence has higher efficiency of ROS generation by both the KI method and the luminol reaction emission. (C) 2016 The Japan Society of Applied Physics

  53. Detection of tissue coagulation by decorrelation of ultrasonic echo signals in cavitation-enhanced high-intensity focused ultrasound treatment Peer-reviewed

    Shin Yoshizawa, Keiko Matsuura, Ryo Takagi, Mariko Yamamoto, Shin-Ichiro Umemura

    Journal of Therapeutic Ultrasound　4　(1)　15　2016

    Publisher: BioMed Central Ltd.

    DOI： 10.1186/s40349-016-0060-0 　

    ISSN：2050-5736

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    Background: A noninvasive technique to monitor thermal lesion formation is necessary to ensure the accuracy and safety of high-intensity focused ultrasound (HIFU) treatment. The purpose of this study is to ultrasonically detect the tissue change due to thermal coagulation in the HIFU treatment enhanced by cavitation microbubbles. Methods: An ultrasound imaging probe transmitted plane waves at a center frequency of 4.5 MHz. Ultrasonic radio-frequency (RF) echo signals during HIFU exposure at a frequency of 1.2 MHz were acquired. Cross-correlation coefficients were calculated between in-phase and quadrature (IQ) data of two B-mode images with an interval time of 50 and 500 ms for the estimation of the region of cavitation and coagulation, respectively. Pathological examination of the coagulated tissue was also performed to compare with the corresponding ultrasonically detected coagulation region. Results: The distribution of minimum hold cross-correlation coefficient between two sets of IQ data with 50-ms intervals was compared with a pulse inversion (PI) image. The regions with low cross-correlation coefficients approximately corresponded to those with high brightness in the PI image. The regions with low cross-correlation coefficients in 500-ms intervals showed a good agreement with those with significant change in histology. Conclusions: The results show that the regions of coagulation and cavitation could be ultrasonically detected as those with low cross-correlation coefficients between RF frames with certain intervals. This method will contribute to improve the safety and accuracy of the HIFU treatment enhanced by cavitation microbubbles.

  54. Effect of controlled offset of focal position in cavitation-enhanced high-intensity focused ultrasound treatment Peer-reviewed

    Kota Goto, Ryo Takagi, Takuya Miyashita, Hayato Jimbo, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　54　(7)　07HF12　2015/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.54.07HF12 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) is a noninvasive treatment for tumors such as cancer. In this method, ultrasound is generated outside the body and focused to the target tissue. Therefore, physical and mental stresses on the patient are minimal. A drawback of the HIFU treatment is a long treatment time for a large tumor due to the small therapeutic volume by a single exposure. Enhancing the heating effect of ultrasound by cavitation bubbles may solve this problem. However, this is rather difficult because cavitation clouds tend to be formed backward from the focal point while ultrasonic intensity for heating is centered at the focal point. In this study, the focal points of the trigger pulses to generate cavitation were offset forward from those of the heating ultrasound to match the cavitation clouds with the heating patterns. Results suggest that the controlled offset of focal points makes the thermal coagulation more predictable. (C) 2015 The Japan Society of Applied Physics

  55. Basic study of intrinsic elastography: Relationship between tissue stiffness and propagation velocity of deformation induced by pulsatile flow Peer-reviewed

    Ryo Nagaoka, Ryosuke Iwasaki, Mototaka Arakawa, Kazuto Kobayashi, Shin Yoshizawa, Shin-ichiro Umemura, Yoshifumi Saijo

    JAPANESE JOURNAL OF APPLIED PHYSICS　54　(7)　07HF08　2015/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.54.07HF08 　

    ISSN：0021-4922

    eISSN：1347-4065

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    We proposed an estimation method for a tissue stiffness from deformations induced by arterial pulsation, and named this proposed method intrinsic elastography (IE). In IE, assuming that the velocity of the deformation propagation in tissues is closely related to the stiffness, the propagation velocity (PV) was estimated by spatial compound ultrasound imaging with a high temporal resolution of 1 ms. However, the relationship between tissue stiffness and PV has not been revealed yet. In this study, the PV of the deformation induced by the pulsatile pump was measured by IE in three different poly(vinyl alcohol) (PVA) phantoms of different stiffnesses. The measured PV was compared with the shear wave velocity (SWV) measured by shear wave imaging (SWI). The measured PV has trends similar to the measured SWV. These results obtained by IE in a healthy male show the possibility that the mechanical properties of living tissues could be evaluated by IE. (C) 2015 The Japan Society of Applied Physics

  56. Quantitative assessment of reactive oxygen sonochemically generated by cavitation bubbles Peer-reviewed

    Jun Yasuda, Takuya Miyashita, Kei Taguchi, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　54　(7)　07HF21　2015/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.54.07HF21 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Acoustic cavitation bubbles can induce not only a thermal bioeffect but also a chemical bioeffect. When cavitation bubbles collapse and oscillate violently, they produce reactive oxygen species (ROS) that cause irreversible changes to the tissue. A sonosensitizer can promote such ROS generation. A treatment method using a sonosensitizer is called sonodynamic treatment. Rose bengal (RB) is one of the sonosensitizers whose in vivo and in vitro studies have been reported. In sonodynamic treatment, it is important to produce ROS at a high efficiency. For the efficient generation of ROS, a triggered high-intensity focused ultrasound (HIFU) sequence has been proposed. In this study, cavitation bubbles were generated in a chamber where RB solution was sealed, and a high-speed camera captured the behavior of these cavitation bubbles. The amount of ROS was also quantified by a potassium iodide (KI) method and compared with high-speed camera pictures to investigate the effectiveness of the triggered HIFU sequence. As a result, ROS could be obtained efficiently by this sequence. (C) 2015 The Japan Society of Applied Physics

  57. Effects of cavitation-enhanced heating in high-intensity focused ultrasound treatment on shear wave imaging Peer-reviewed

    Ryosuke Iwasaki, Ryo Nagaoka, Ryo Takagi, Kota Goto, Shin Yoshizawa, Yoshifumi Saijo, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　54　(7)　07HF11　2015/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.54.07HF11 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) therapy is a less invasive method of cancer treatment, in which ultrasound is generated outside the body and focused at the tumor tissue to be thermally coagulated. To enhance the safety, accuracy, and efficiency of HIFU therapy, "multiple-triggered HIFU" has been proposed as a method of cavitation-enhanced heating to shorten treatment time. In this study, we also propose shear wave elastography (SWE) to noninvasively monitor the cavitation-enhanced heating. Results show that the increase in shear wave velocity was observed in the coagulation area, but it was significantly slower when cavitation occurred. This suggests that the cavitation-enhanced heating requires a significantly longer cooling time before the accurate measurement of shear modulus than heating without generating bubbles. (C) 2015 The Japan Society of Applied Physics

  58. Quantitative measurement of high intensity focused ultrasound pressure field by optical phase contrast method applying non-continuous phase unwrapping algorithm Peer-reviewed

    Mohd Syahid, Seiji Oyama, Jun Yasuda, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　54　(7)　07HC09　2015/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.54.07HC09 　

    ISSN：0021-4922

    eISSN：1347-4065

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    A fast and accurate ultrasound pressure field measurement is necessary for the progress of ultrasound application in medicine. In general, a hydrophone is used to measure the ultrasound field, which takes a long measurement time and might disturb the ultrasound field. Hence, we proposed a new method categorized in an optical method called Phase Contrast method to overcome the drawback in the hydrophone method. The proposed method makes use of the spatial DC spectrum formed in the focal plane to measure the modulated optical phase induced by ultrasound propagation in water. In this study, we take into account the decreased intensity of the DC spectrum at high ultrasound intensity to increase the measurement accuracy of the modulated optical phase. Then, we apply a non-continuous phase unwrapping algorithm to unwrap the modulated optical phase at high ultrasound intensity. From, the unwrapped result, we evaluate the quantitativeness of the proposed method. (C) 2015 The Japan Society of Applied Physics

  59. Elimination of therapeutic ultrasound noise from pre-beamformed RF data in ultrasound imaging for ultrasound-guided high-intensity focused ultrasound treatment Peer-reviewed

    Ryo Takagi, Kota Goto, Hayato Jimbo, Keiko Matsuura, Ryosuke Iwasaki, Shin-ichiro Umemura, Shin Yoshizawa

    JAPANESE JOURNAL OF APPLIED PHYSICS　54　(7)　07HD10　2015/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.54.07HD10 　

    ISSN：0021-4922

    eISSN：1347-4065

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    In conventional ultrasonic monitoring of high-intensity focused ultrasound (HIFU) treatment, a significant interval between consecutive HIFU shots is set for monitoring target tissue to avoid the interference of HIFU noise with RF echo signals. Thus, it is difficult to detect changes in tissue on the order of milliseconds, which are required to dynamically control the HIFU exposure. In this study, a new filtering method to eliminate the HIFU noise in the RF signals before beamforming is proposed. The CW response was estimated from RF signals with no pulse response to the imaging exposure, and the estimated CW response was subtracted from the entire RF signal to selectively eliminate the HIFU noise for each channel of the array probe before dynamic focusing was applied. The HIFU noise was selectively eliminated by this method when it existed. The results imply that the proposed filtering method is useful for true real-time detection of changes in tissue due to thermal coagulation during HIFU exposure. (C) 2015 The Japan Society of Applied Physics

  60. Measurement of regional pulse-wave velocity using spatial compound imaging of the common carotid artery in vivo Peer-reviewed

    Ryo Nagaoka, Genta Masuno, Kazuto Kobayashi, Shin Yoshizawa, Shin-ichiro Umemura, Yoshifumi Saijo

    ULTRASONICS　55　(1)　92-103　2015/01

    Publisher: ELSEVIER SCIENCE BV

    DOI： 10.1016/j.ultras.2014.07.018 　

    ISSN：0041-624X

    eISSN：1874-9968

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    Pulse-wave velocity (PWV) is an important index for diagnosing cardiovascular diseases. The pulse wave is volumetric change induced by heartbeat or inflowing blood, and significantly depends on the propagating path and stiffness of the artery. In this study, PWV of the propagating wave was visualized using spatial compound imaging with high temporal resolution. The frame rate was 1000 Hz, or a time interval of 1 ms. Subjects were four young healthy males and one young healthy female (n = 5, age: 23.8 +/- 1.17 years old), and the measurement area was the right common carotid artery. PWVs in four phases (the four phases of heart valve opening and closing) were investigated during a cardiac cycle. In phase I, the heart pulsates. In phase II, the tricuspid and mitral valves close, and the aortic and pulmonic valves open. In phase III, the tricuspid and mitral valves open, and the aortic and pulmonic valves close. In phase IV, the propagating wave is reflected. PWVs in phases II and III were easily observed. PWVs were 3.52 +/- 1.11 m/s in phase I, 5.62 +/- 0.30 m/s in phase II, 7.94 +/- 0.85 m/s in phase III, and -4.60 +/- 0.99 m/s for the reflective wave. PWV was measured using Spatial Compound Imaging with high temporal resolution, and the PWV in each phase may be used as the index for diagnosing stages of arteriosclerosis progression. (C) 2014 Elsevier B.V. All rights reserved.

  61. Monitoring of high-intensity focused ultrasound lesion formation using decorrelation between high-speed ultrasonic images by parallel beamforming Peer-reviewed

    Shoya Sasaki, Ryo Takagi, Keiko Matsuura, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　53　(7)　07KF10　2014/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.53.07KF10 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) is a type of therapeutic treatment in which ultrasound is focused to a target tissue such as cancer to be thermally coagulated. To enhance the safety and accuracy of HIFU treatment, a noninvasive method of monitoring the thermal lesion formation is important. A potential method for this purpose is ultrasound imaging. In this study, high-speed imaging by parallel beamforming was performed using ultrasound RF signals acquired during HIFU exposure, and the distribution of the cross-correlation coefficient between RF frames was calculated to estimate the tissue coagulation. Using high-speed imaging, HIFU can be irradiated quasi-continuously. The result shows that the decorrelation was observed at and around the focal spot of HIFU exposure. The decorrelation was induced by the change in RF signals owing to tissue coagulation, which was confirmed by the fact that the emergence and increase in the number of decorrelated pixels at and around the focal spot corresponded to the start and progress of tissue coagulation. (C) 2014 The Japan Society of Applied Physics

  62. Quantitative measurement of focused ultrasound pressure field by background-subtracted shadowgraph using holographic diffuser as screen Peer-reviewed

    Ryo Miyasaka, Jun Yasuda, Mohd Syahid, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　53　(7)　07KF24　2014/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.53.07KF24 　

    ISSN：0021-4922

    eISSN：1347-4065

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    In the development of medical ultrasound techniques, fast and accurate pressure field measurement is important. The most common method of measuring an ultrasound pressure field is by using a mechanically scanned hydrophone, which might disturb the acoustic field, and it takes a long time. In this study, we used an optical shadowgraph method. For quantitative measurement using the shadowgraph, it is important to define precisely the optical propagation length between the phase object and the imaging plane. We used a holographic diffuser as the imaging screen for this purpose. A computed tomography (CT) algorithm was used to reconstruct a pressure field, and the result was compared with that of hydrophone measurement. By combining two shadowgraph results from smaller and larger propagation lengths, the result was very close to that of the hydrophone and was successfully reconstructed in the pressure range where nonlinear deformation was clear. (C) 2014 The Japan Society of Applied Physics

  63. Effects of rose bengal on cavitation generation in gel phantom investigated using high-speed camera Peer-reviewed

    Jun Yasuda, Takuya Miyashita, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　53　(7)　07KF20　2014/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.53.07KF20 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Acoustic cavitation bubbles are microbubbles generated by the highly negative pressure of ultrasound. They are known to enhance the thermal bioeffect of high-intensity focused ultrasound (HIFU) treatment. Other than the use of the thermal bioeffect, sonodynamic treatment using the sonochemical bioeffect of ultrasound has been proposed. In sonodynamic treatment, a sonosensitizer is activated through the collapse of cavitation bubbles to induce a therapeutic effect sonochemically. Rose Bengal (RB) has the potential to be such a sonosensitizer. Highly efficient as well as controlled generation of cavitation bubbles is crucial for realizing effective as well as safe sonodynamic treatment. The effect of RB on cavitation generation was investigated to achieve such controlled generation. The amount and behavior of the cavitation bubbles generated by a triggered HIFU sequence in the presence of RB were observed using a high-speed camera for estimating the effect of RB. Results showed that RB increased the area of the cavitation cloud and the lifetime of sustained cavitation bubbles. (C) 2014 The Japan Society of Applied Physics

  64. Highly efficient cavitation-enhanced heating with dual-frequency ultrasound exposure in high-intensity focused ultrasound treatment Peer-reviewed

    Hiroshi Sasaki, Jun Yasuda, Ryo Takagi, Takuya Miyashita, Kota Goto, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　53　(7)　07KF11　2014/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.53.07KF11 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) treatment is a noninvasive therapy for malignant as well as benign tumors. In this method, the ultrasound is generated outside the body and focused to the target tissue. Therefore, physical and mental stresses on the patient are minimal. A drawback of HIFU therapy is the long treatment time for a large tumor owing to a small therapeutic volume by a single exposure. Enhancing the heating effect of ultrasound by cavitation bubbles may solve this problem. They are generated by high-intensity ultrasound exposure and can convert the acoustic energy into heat at a high efficiency. In this study, we combined "dual-frequency ultrasound exposure" for the efficient generation and expansion of a cavitation bubble cloud, and "multiple-triggered HIFU" for the efficient enhancement of ultrasonic heating. The result suggests that the newly proposed combined method is more efficient than the conventional triggered HIFU method. (C) 2014 The Japan Society of Applied Physics

  65. High-speed observation of bubble cloud generation near a rigid wall by second-harmonic superimposed ultrasound Peer-reviewed

    Shin Yoshizawa, Jun Yasuda, Shin-ichiro Umemura

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA　134　(2)　1515-1520　2013/08

    Publisher: ACOUSTICAL SOC AMER AMER INST PHYSICS

    DOI： 10.1121/1.4812870 　

    ISSN：0001-4966

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    Cavitation bubbles are known to accelerate therapeutic effects of ultrasound. Although negative acoustic pressure is the principle factor of cavitation, positive acoustic pressure has a role for bubble cloud formation at a high intensity of focused ultrasound when cavitation bubbles provide pressure release surfaces converting the pressure from highly positive to negative. In this study, the second-harmonic was superimposed onto the fundamental acoustic pressure to emphasize either peak positive or negative pressure. The peak negative and positive pressure emphasized waves were focused on a surface of an aluminum block. Cavitation bubbles induced near the block were observed with a high-speed camera by backlight and the size of the cavitation generation region was measured from the high-speed images. The negative pressure emphasized waves showed an advantage in cavitation inception over the positive pressure emphasized waves. In the sequence of the negative pressure emphasized waves immediately followed by the positive pressure emphasized waves, cavitation bubbles were generated on the block by the former waves and the cavitation region were expanded toward the transducer in the latter waves with high reproducibility. The sequence demonstrated its potential usefulness in enhancing the effects of therapeutic ultrasound at a high acoustic intensity. (C) 2013 Acoustical Society of America.

  66. Changes in backscatter of liver tissue due to thermal coagulation induced by focused ultrasound Peer-reviewed

    Takashi Shishitani, Ryo Matsuzawa, Shin Yoshizawa, Shin-ichiro Umemura

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA　134　(2)　1724-1730　2013/08

    Publisher: ACOUSTICAL SOC AMER AMER INST PHYSICS

    DOI： 10.1121/1.4813104 　

    ISSN：0001-4966

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    Ultrasonic imaging has advantages in its self-consistency in guiding and monitoring ultrasonic treatment such as high-intensity focused ultrasound (HIFU) treatment. Changes in ultrasonic backscatter of tissues due to HIFU treatment have been observed, but their mechanism is still under discussion. In this paper, ultrasonic backscatter of excised and degassed porcine liver tissue was observed before and after HIFU exposure using a diagnostic scanner, and its acoustic impedance was mapped using an ultrasonic microscope. The histology of its pathological specimen was also observed using an optical microscope. The observed decrease in backscatter intensity due to HIFU exposure was consistent with a spatial Fourier analysis of the histology, which also showed changes due to the exposure. The observed increase in acoustic impedance due to the exposure was also consistent with the histological change assuming that the increase was primarily caused by the increase in the concentration of hepatic cells. (C) 2013 Acoustical Society of America.

  67. Optical Phase Contrast Mapping of Highly Focused Ultrasonic Fields Peer-reviewed

    Soichiro Harigane, Ryo Miyasaka, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　52　(7)　07HF07　2013/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.52.07HF07 　

    ISSN：0021-4922

    eISSN：1347-4065

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    The most common method of measuring an ultrasonic pressure field is a hydrophone scan. However, this method has a long scanning time and disturbs the acoustic field. In this study, we used an optical phase contrast method for the measurement. Because this method uses light, fast and noninvasive measurement can be performed. The projections of an ultrasonic pressure field were obtained with a charge-coupled device (CCD) camera, and the three-dimensional (3D) acoustic pressure field was reconstructed using a computed tomography (CT) algorithm from these projections. The result was compared with that of hydrophone measurement and demonstrated the successful reconstruction of a focal ultrasonic pressure field. (c) 2013 The Japan Society of Applied Physics

  68. Large Volume Coagulation Utilizing Multiple Cavitation Clouds Generated by Array Transducer Driven by 32 Channel Drive Circuits Peer-reviewed

    Kotaro Nakamura, Ayumu Asai, Hiroshi Sasaki, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　52　(7)　07HF10　2013/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.52.07HF10 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) treatment is a noninvasive treatment, in which focused ultrasound is generated outside the body and coagulates a diseased tissue. The advantage of this method is minimal physical and mental stress to the patient, and the disadvantage is the long treatment time caused by the smallness of the therapeutic volume by a single exposure. To improve the efficiency and shorten the treatment time, we are focusing attention on utilizing cavitation bubbles. The generated microbubbles can convert the acoustic energy into heat with a high efficiency. In this study, using the class D amplifiers, which we have developed, to drive the array transducer, we demonstrate a new method to coagulate a large volume by a single HIFU exposure through generating cavitation bubbles distributing in a large volume and vibrating all of them. As a result, the coagulated volume by the proposed method was 1.71 times as large as that of the conventional method. (C) 2013 The Japan Society of Applied Physics

  69. Enhancement of Focused Ultrasound Treatment by Acoustically Generated Microbubbles Peer-reviewed

    Shin-ichiro Umemura, Shin Yoshizawa, Ryo Takagi, Yuta Inaba, Jun Yasuda

    JAPANESE JOURNAL OF APPLIED PHYSICS　52　(7)　07HA02　2013/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.52.07HA02 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Microbubbles, whether introduced from outside the body or ultrasonically generated in situ, are known to significantly enhance the biological effects of ultrasound, including the mechanical, thermal, and sonochemical effects. Phase-change nanodroplets, which selectively accumulate in tumor tissue and whose phase changes to microbubbles can be induced by ultrasonic stimulation, have been proposed for high-intensity focused ultrasound (HIFU) tumor treatment with enhanced selectivity and efficiency. In this paper, a purely acoustic approach to generate microbubble clouds in the tissue to be treated is proposed. Short pulses of focused ultrasound with extremely high intensity, named trigger pulses, are used for exposure. They are immediately followed by focused ultrasound for heating with an intensity similar to or less than that of normal HIFU treatment. The localized generation of microbubble clouds by the trigger pulses is observed in a polyarylamide gel by a high-speed camera, and the effectiveness of the generated clouds in accelerating ultrasonically induced thermal coagulation is confirmed in excised chicken breast tissue. The use of second-harmonic superimposed waves as the trigger pulses is also proposed. The highly reproducible initiation of cavitation by waves with the negative peak pressure emphasized and the efficient expansion of the generated microbubble clouds by waves with the positive peak pressure emphasized are also observed by a high-speed camera in partially degassed water. (c) 2013 The Japan Society of Applied Physics

  70. Efficient Generation of Cavitation Bubbles in Gel Phantom by Ultrasound Exposure with Negative-Followed by Positive-Peak-Pressure-Emphasized Waves Peer-reviewed

    Jun Yasuda, Ayumu Asai, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　52　(7)　07HF11　2013/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.52.07HF11 　

    ISSN：0021-4922

    eISSN：1347-4065

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    Cavitation bubbles have much potential for emphasizing therapeutic treatments such as high-intensity focused ultrasound (HIFU) treatment, histotripsy, and sonodynamic therapy. Their highly efficient as well as controlled generation is important to utilize them effectively as well as safely. However, producing negative pressure over the cavitation threshold by focused ultrasound is difficult because of the nonlinear propagation combined with the focal phase shift. We have suggested a dual-frequency ultrasound exposure method, in which N- and P-waves emphasizing either the peak negative or positive pressure, respectively, are synthesized by superimposing the second harmonic onto the fundamental frequency. In this study, high-speed camera observation demonstrated that the exposure with N-waves immediately followed by P-waves could generate cavitation bubbles most efficiently in gel phantom. Furthermore, the measured negative and positive pressure distributions of the N- and P-wave fields, respectively, agreed well with the optically observed distributions of cavitation inception and cavitation cloud growth. (C) 2013 The Japan Society of Applied Physics

  71. Analysis of Temperature Rise Induced by High-Intensity Focused Ultrasound in Tissue-Mimicking Gel Considering Cavitation Bubbles Peer-reviewed

    Ayumu Asai, Hiroki Okano, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　52　(7)　07HF02　2013/07

    Publisher: IOP PUBLISHING LTD

    DOI： 10.7567/JJAP.52.07HF02 　

    ISSN：0021-4922

    eISSN：1347-4065

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    High-intensity focused ultrasound (HIFU) causes a selective temperature rise in tissue and is used as a noninvasive method for tumor treatment. However, there is a problem in that it typically takes several hours to treat a large tumor. The development of a highly efficient method is required to shorten the treatment time. It is known that cavitation bubbles generated by HIFU enhance HIFU heating. In this study, the enhancement of the heating effect by cavitation was estimated in a numerical simulation solving a bio-heat transfer equation (BHTE) by increasing the absorption coefficients in and out of the volume of cavitation bubbles. The absorption coefficients were obtained by a curve fitting the temperature rise near the focal point between experiment and simulation. The results show that cavitation bubbles caused the increase in ultrasonic absorption not only in but also near the volume of cavitation bubbles. (c) 2013 The Japan Society of Applied Physics

  72. Therapeutic Array Transducer Element Using Coresonance between Hemispherical Piezoceramic Shell and Water Sphere: Effect of Load Masses of Support and Electric Contact Peer-reviewed

    Kenji Otsu, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　51　(7)　07GF24　2012/07

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.51.07GF24 　

    ISSN：0021-4922

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    For therapeutic ultrasound array transducers, it is necessary to reduce the electrical impedance of their elements so that the transducer can produce high ultrasonic power at a relatively low drive voltage. For this purpose, a new concept of a breathing-mode piezoceramic transducer element has been proposed. Numerical simulation showed its low electric impedance as well as good acoustical coupling between the concave hemispherical piezoceramic shell, with a diameter on the order of a wavelength in water, and the volume of a water sphere half enclosed by the shell. In the preparation of a prototype transducer, the effect of additional load masses of the flange supporting the shell and the electric contact for driving the element was numerically analyzed in this paper. (C) 2012 The Japan Society of Applied Physics

  73. Three-Dimensional Quantitative Optical Measurement of Asymmetrically Focused Ultrasound Pressure Field Peer-reviewed

    Yuta Shimazaki, Soichiro Harigane, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　51　(7)　07GF25　2012/07

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.51.07GF25 　

    ISSN：0021-4922

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    High-intensity focused ultrasound (HIFU) is used for the treatment of tumors such as prostate cancer. In the development of this technique, an accurate and fast measurement of the HIFU pressure field is important. A hydrophone is generally used for the measurement, but it might disturb the pressure field and scanning it in the field takes a long time. On the other hand, optical ultrasonic field mapping has the advantages of speed and its nature of not by interfering with the acoustic field. In this study, we reconstructed an asymmetric ultrasound field by optical measurement using a computed tomography (CT) algorithm. The asymmetric field was generated by a focused transducer with four elements. Also, the absolute measurement of ultrasonic pressure was checked by measuring the center of the field of the charge-coupled device (CCD) camera. The results showed overall agreement with those of hydrophone measurement. (C) 2012 The Japan Society of Applied Physics

  74. Thermal Simulation of Cavitation-Enhanced Ultrasonic Heating Verified with Tissue-Mimicking Gel Peer-reviewed

    Tatsuya Moriyama, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　51　(7)　07GF27　2012/07

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.51.07GF27 　

    ISSN：0021-4922

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    High-intensity focused ultrasound (HIFU) causes selective tissue necrosis through heating and is used as a noninvasive treatment in cancer therapy. However, there is a problem that it takes several hours to treat a large tumor. To shorten the treatment time, there is need for the development of a highly efficient method. It is known that cavitation bubbles generated by HIFU enhance the heating effect of ultrasound. In this study, the enhancement of the heating effect due to cavitation was considered in the bio-heat transfer equation (BHTE) by increasing the absorption coefficient in the region of generated cavitation. The absorption coefficient was calculated by curve fitting between the temperature rise at the focal point in the experiment and that in the simulation. The results show that the increased absorption can simulate the enhancement of the temperature rise by cavitation bubbles. (C) 2012 The Japan Society of Applied Physics

  75. High Voltage Staircase Drive Circuit for Triggered High-Intensity Focused Ultrasound Treatment Peer-reviewed

    Keisuke Takada, Jumpei Okada, Kotaro Nakamura, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　51　(7)　07GF23　2012/07

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.51.07GF23 　

    ISSN：0021-4922

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    In triggered high-intensity focused ultrasound (HIFU) treatment, cavitation clouds are produced by extremely high intensity trigger pulses and enhance the effect of following heating waves. The ultrasound intensity must be quickly changed from that for trigger pulses to that for heating waves before cavitation clouds vanish. We newly designed and constructed a class D amplifier based on a staircase voltage drive concept, which has the capability of outputting high voltage waves for trigger pulses and continuous waves for heating waves and the capability of fast switching between the two modes. Its efficacy was confirmed by an experiment with a BSA containing polyacrylamide gel. (C) 2012 The Japan Society of Applied Physics

  76. Monitoring of Lesion Induced by High-Intensity Focused Ultrasound Using Correlation Method Based on Block Matching Peer-reviewed

    Ryo Matsuzawa, Takashi Shishitani, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　51　(7)　07GF26　2012/07

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.51.07GF26 　

    ISSN：0021-4922

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    High-intensity focused ultrasound (HIFU) is a noninvasive therapeutic application that focuses ultrasound to the target tissue, such as a malignant tumor, and thermally coagulates it. Monitoring methods for evaluating the formation of thermal lesions induced by HIFU are required to perform safe and accurate HIFU treatment. However, the conventional ultrasonic B-mode image incurs difficulties in assessing the formation of HIFU-induced lesions. In this study, ultrasound RF signals were acquired during HIFU exposure. A correlation coefficient was used to evaluate the changes occurring in the RF signals backscattered from the thermal lesion. Also, a block matching algorithm has been implemented to compensate the tissue motion during HIFU exposure. The experimental results show that correlation coefficients in the focal spot decreased significantly with HIFU exposure, which indicates that the backscattered RF signals changed owing to tissue coagulation. (C) 2012 The Japan Society of Applied Physics

  77. Quantitative Measurement of Focused Ultrasound Pressure Field Using Subtraction Shadowgraph Peer-reviewed

    Ryosuke Omura, Yuta Shimazaki, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　50　(7)　07HC07　2011/07

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.50.07HC07 　

    ISSN：0021-4922

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    In this study, the measurement of focused ultrasound pressure field by the subtraction shadowgraph method was investigated. Conventional shadowgraph is known as a fast, noninvasive, but qualitative method of ultrasound pressure field measurement. On the other hand, the subtraction shadowgraph method in this paper can provide quantitative projection images, from which the ultrasound pressure field can be reconstructed. Subtraction shadowgraph images of a focused ultrasound field were obtained, it was converted to the projection of the refractory distribution, and the focused ultrasound pressure field was reconstructed from the projection by computed tomography algorithm. The result was compared with that of hydrophone measurement, and successful reconstruction of the axi-symmetric pressure distribution of the focal field was confirmed in both lateral and axial cross sections. (C) 2011 The Japan Society of Applied Physics

  78. Breathing-Mode Ceramic Element for Therapeutic Array Transducer Peer-reviewed

    Kenji Otsu, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　50　(7)　07HC02　2011/07

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.50.07HC02 　

    ISSN：0021-4922

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    A new concept of piezoceramic array transducer element using breathing mode has been proposed for therapeutic application. Finite element numerical simulation showed that a concave hemispherical piezoceramic shell with a diameter slightly larger than the wavelength in water is effective for obtaining good acoustic matching with water. A hemispherical piezoceramic element with an inner diameter of 4.0mm and a thickness of 0.2-0.4mm produced more than several times higher acoustic power output than a conventional thickness-mode element at the same drive voltage in the simulation. Its good acoustic matching with water is considered to be accomplished by the combined resonance with the spherical bulk of water half covered by the shell, because the resonance was very sensitive to the change in sound speed of the virtual material replacing water with the same acoustic impedance in simulation. (C) 2011 The Japan Society of Applied Physics

  79. Ultrasonic Coagulation of Large Tissue Region by Generating Multiple Cavitation Clouds in Direction Perpendicular to Ultrasound Propagation Peer-reviewed

    Yuta Inaba, Moriyama Tatsuya, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　50　(7)　07HF13　2011/07

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.50.07HF13 　

    ISSN：0021-4922

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    High-intensity focused ultrasound (HIFU) therapy is attracting attention as a minimally invasive therapeutic modality. However, it has a problem of a long treatment time. To improve the efficiency of the treatment, we developed a method of coagulating a large region at one time utilizing multiple clouds of cavitation. It is known that acoustic cavitation generated in the focal region of HIFU enhances tissue heating. In this study, cavitation clouds were generated at three positions in the direction perpendicular to ultrasound propagation using high-intensity ultrasound pulses. The tissue in the vicinity of the cavitation clouds was coagulated simultaneously with nonspherically focused ultrasound waves at a relatively low intensity. A high-speed camera was used to observe such behavior of cavitation clouds in a tissue-mimicking gel and to optimize the sequence, and the coagulation performance of the sequence was confirmed with an experiment using excised tissue. The result suggests that the HIFU treatment time is significantly shortened by employing the proposed method. (C) 2011 The Japan Society of Applied Physics

  80. Sonodynamic Therapy with 5-Aminolevulinic Acid and Focused Ultrasound for Deep-seated Intracranial Glioma in Rat Peer-reviewed

    Tadahiro Ohmura, Takeo Fukushima, Hirotomo Shibaguchi, Shin Yoshizawa, Tooru Inoue, Masahide Kuroki, Kazunari Sasaki, Shin-Ichiro Umemura

    ANTICANCER RESEARCH　31　(7)　2527-2533　2011/07

    Publisher: INT INST ANTICANCER RESEARCH

    ISSN：0250-7005

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    Background: 5-Aminolevulinic acid (5-ALA) has already been applied clinically as a photosensitizer. In this study, sonodynamically induced selective antitumour effect of 5-ALA for deep-seated lesions was evaluated. Materials and Methods: First, normal rat brains were sonicated via a transducer placed on the dural surface to confirm safe acoustic conditions for normal rat brains. One week after inoculation of brains with C6 rat glioma cells, brains with/without administration of 5-ALA (100 mg/kg body weight) were sonicated. Results: Sonodynamic therapy (SDT) with 5-ALA and focused ultrasound (10 W/cm(2), 1.04 MHz, 5 min) achieved selective antitumour effect against deep-seated experimental glioma. Mean tumour sizes in the largest coronal section in sham-operated rats and rats receiving ultrasound with/without 5-ALA were 29.94 +/- 10.39, 18.32 +/- 5.69 and 30.81 +/- 9.65 mm(2), respectively. Tumour size was significantly smaller in the SDT group than in other groups (p<0.05). Conclusion: This experimental rat model showed that SDT appears to be useful in the treatment of deep-seated malignant glioma.

  81. Analysis of High-Intensity Focused Ultrasound Source Using Time Reversal: Effect of Lamb-Like Waves Peer-reviewed

    Yasuhiro Kaneshima, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　50　(4)　047301　2011/04

    Publisher: IOP PUBLISHING LTD

    DOI： 10.1143/JJAP.50.047301 　

    ISSN：0021-4922

    eISSN：1347-4065

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    The pressure distribution of a focused ultrasound source was reconstructed from a measured pressure field on the focal plane using time-reversal. The two-dimensional Fourier transform of the distribution in the time and space domain showed a peak with a finite phase velocity, which corresponds to a mode of waves propagating from the circumference to the center of the transducer similar to Lamb waves. It was numerically confirmed that the propagating waves significantly enhanced the secondary lobe on the near side of the main focal lobe. The near side lobe was markedly reduced by increasing the thickness of the transducer by three times in the experiment. This significant change is consistent with the hypothesis that the near side lobe was formed by Lamb-like waves. (C) 2011 The Japan Society of Applied Physics

  82. Cavitation inception by dual-frequency excitation in high-intensity focused ultrasound treatment Peer-reviewed

    Takagi, R.a, Yoshizawa, S., Umemura, S.-I

    Jpn. J. Appl. Phys.　50　(7 PART 2)　07HF14-07HF14-5　2011

    Publisher: The Japan Society of Applied Physics

    DOI： 10.1143/JJAP.50.07HF14 　

    ISSN：0021-4922

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    In our previous study, we proposed a "triggered high-intensity focused ultrasound (HIFU)" exposure sequence, in which a high-intensity triggering pulse was irradiated just before CW heating waves, to accelerate HIFU treatment. In this study, the second-harmonic was superimposed to the triggering pulse, and the cavitation threshold was investigated by comparing different schemes of second-harmonic superimposition including the case of single-frequency exposure through detecting the subharmonic emission and high-speed camera observation. The experimental results show that cavitation bubbles can be generated most efficiently by using negative-peak-pressure emphasized waves followed by positive-peak-pressure emphasized waves.

  83. The influence of the insonation conditions of pulsed ultrasound on microbubble volumetric oscillations (On the mechanical index and the oscillation characteristics) Peer-reviewed

    Takeshi Miyamoto, Shin Yoshizawa, Yoichiro Matsumoto

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B　77　(774)　264-273　2011

    DOI： 10.1299/kikaib.77.264 　

    ISSN：0387-5016

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    The influence of the insonation conditions of short-pulse and low-duty diagnostic ultrasound on the characteristics of microbubble volumetric oscillations in the initial bubble radius range from 0.2 to 2.0 micro meters has been numerically investigated by using a recent single bubble oscillation model. The results show that increasing insonation center frequencies with the constant values of the mechanical index reduces the maximum values of both of the in-bubble temperatures and the bubble-emitted sound pressures increasing the values of that index with constant center frequencies reduces the resonant bubble radii the maximum in-bubble temperatures and bubble-emitted pressures are correlated with the normalized minimum bubble radii more significantly than the normalized maximum radii. © 2011 The Japan Society of Mechanical Engineers.

  84. Enhancement of localized heating by ultrasonically induced cavitation in high intensity focused ultrasound treatment Peer-reviewed

    Ryo Takagi, Shin Yoshizawa, Shin-Ichiro Umemura

    Japanese Journal of Applied Physics　49　(7)　07HF21　2010/07

    DOI： 10.1143/JJAP.49.07HF21 　

    ISSN：0021-4922 1347-4065

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    There are reports that ultrasonically induced cavitation bubbles locally enhance tissue heating in high intensity focused ultrasound (HIFU) treatment. In this study, a high-intensity burst (named "a triggering pulse") above the cavitation threshold was used to trigger cavitation. Immediately after that, CW ultrasound (named "heating waves"), at an intensity level and duration typical for conventional HIFU ablation was irradiated. Before the ablating sonication, it is necessary to determine the optimum intensity and duration of the triggering pulse. Immediately after a test triggering pulse, low-intensity CW ultrasound (named "a sustaining pulse") was irradiated for a short duration of time, and we detected the cavitation noises (subharmonics and higher harmonics) generated in the focus spot. The relationship between the 1/2 subharmonic signal amplitude and the coagulation volume after the ablating sonication was investigated. The result of this experiment suggests that we can optimize the triggering pulse by detecting the 1/2 subharmonic signal amplitude. © 2010 The Japan Society of Applied Physics.

  85. Staircase-Voltage Metal-Oxide-Semiconductor Field-Effect Transistor Driver Circuit for Therapeutic Ultrasound Peer-reviewed

    Kosuke Moro, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　49　(7)　07HF02　2010

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.49.07HF02 　

    ISSN：0021-4922

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    An important component of all ultrasound systems is the high-voltage pulse generator used to excite the transducer. We created a new type of metal-oxide-semiconductor field-effect transistor (MOSFET) switching circuit for therapeutic ultrasound applications, on the basis of the staircase-voltage drive concept. The staircase drive can significantly decrease the harmonics in comparison with the conventional square-wave drive. Since it does not require a resonant circuit to improve the efficiency, the drive frequency can be freely changed and the total size of the drive circuit can be made smaller. Using a diode in series to the drain of each MOSFET, a staircase-voltage driver was created with a relatively simple configuration. The experimental results of operating a prototype driver, as well as the results from circuit simulation, are discussed. (C) 2010 The Japan Society of Applied Physics

  86. Coagulation of Large Regions by Creating Multiple Cavitation Clouds for High Intensity Focused Ultrasound Treatment Peer-reviewed

    Yuta Inaba, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　49　(7)　07HF22　2010

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.49.07HF22 　

    ISSN：0021-4922

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    High-Intensity focused ultrasound (HIFU) is attracting attention as a minimally invasive therapeutic modality. However, it has a problem of a long treatment time. To improve its treatment throughput, we developed a method of coagulating a large region at one time utilizing multiple clouds of cavitation. It is known that acoustic cavitation generated in the focal region of HIFU enhances tissue heating. In the experiment in this study, the focal distance was changed using an annular array transducer. Cavitation clouds were generated at three positions within a fraction of a second by high-intensity ultrasound pulses. The tissues in the vicinity of the cavitation clouds were coagulated simultaneously with non-spherically focused ultrasound waves at a relatively low intensity. The result suggests that the HIFU treatment time is significantly shortened by employing the proposed method. (C) 2010 The Japan Society of Applied Physics

  87. Acoustic Impedance Evaluation of High-Intensity-Focused-Ultrasound Exposed Chicken Breast Muscle Using Ultrasonic Microscopy Peer-reviewed

    Takashi Shishitani, Shin Yoshizawa, Shin-ichiro Umemura

    JAPANESE JOURNAL OF APPLIED PHYSICS　49　(7)　07HF04　2010

    Publisher: JAPAN SOC APPLIED PHYSICS

    DOI： 10.1143/JJAP.49.07HF04 　

    ISSN：0021-4922

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    High-intensity focused ultrasound (HIFU) surgery is one of the non-invasive therapeutic methods. The high temperature generated by this method coagulates the target non-superficial tissue. In this study, we evaluate the effect of thermal coagulation by HIFU on acoustic impedance. Chicken breast muscle was used as the specimen. Acoustic impedance was measured in cross sections of the HIFU-exposed specimen using an ultrasonic microscope. The acoustic impedance of the coagulated region was significantly lower than that of the non-coagulated region. (C) 2010 The Japan Society of Applied Physics

  88. High intensity focused ultrasound lithotripsy with cavitating microbubbles Peer-reviewed

    Shin Yoshizawa, Teiichiro Ikeda, Akira Ito, Ryuhei Ota, Shu Takagi, Yoichiro Matsumoto

    MEDICAL & BIOLOGICAL ENGINEERING & COMPUTING　47　(8)　851-860　2009/08

    Publisher: SPRINGER HEIDELBERG

    DOI： 10.1007/s11517-009-0471-y 　

    ISSN：0140-0118

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    In the medical ultrasound field, microbubbles have recently been the subject of much interest. Controlling actively the effect of the microbubbles, a novel therapeutic method has been investigated. In this paper, our works on high intensity focused ultrasound (HIFU) lithotripsy with cavitating microbubbles are reviewed and the cavitation detection method to optimize the HIFU intensity is investigated. In the HIFU lithotripsy, collapse of the cloud cavitation is used to fragment kidney stones. Cloud cavitation is potentially the most destructive form of cavitation. When the cloud cavitation is acoustically forced into a collapse, it has the potential to concentrate a very high pressure. For the control of the cloud cavitation collapse, a novel two-frequency wave (cavitation control [C-C] waveform) is designed; a high-frequency ultrasound pulse (1-4 MHz) to create the cloud cavitation and a low-frequency trailing pulse (500 kHz) following the high-frequency pulse to force the cloud into collapse. High-speed photography showed the cavitation collapse on the stone and the shock-wave emission from the cloud. In vitro erosion tests of model and natural stones were also conducted. In the case of model stones, the erosion rate of the C-C waveform showed a distinct advantage with the combined high- and low-frequency waves over either wave alone. For the optimization of the high-frequency ultrasound intensity, the subharmonic acoustic pressure was examined. The results showed relationship between the subharmonic pressure from cavitating bubbles induced by the high-frequency ultrasound and eroded volume of the model stones. Natural stones were eroded and most of the resulting fragments were less than 1 mm in diameter. The method has the potential to provide a novel lithotripsy system with small fragments and localized cavitating bubbles on a stone.

  89. G1501-1-1 Development of acoustic pressure scanner for the Non-Invasive Ultrasound Theragnostic System by HIFU

    SEO Joonho, KOIZUMI Norihiro, SUZUKI Yugo, NOMIYA Akira, YOSHIZAWA Shin, YOSHINAKA Kiyoshi, SUGITA Naohiko, HOMMA Yukio, MATSUMOTO Yoichiro, MITSUISHI Mamoru

    The proceedings of the JSME annual meeting　2009　131-132　2009

    Publisher: The Japan Society of Mechanical Engineers

    DOI： 10.1299/jsmemecjo.2009.5.0_131 　

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    We propose an automated needle hydrophone based scanning system to obtain high-resolution planar acoustic pressure distribution generated by high intensity focused ultrasound (HIFU). The preoperative scanning plan manipulates the position of HIFU transducer and automates the acquisition of spatial acoustic pressure distribution. In particular, a method to minimize the displacement error induced by the time delay improves the scanning speed problem of the conventional needle hydrophone based scan system. Moreover, the noise-robust and automatic focus searching algorithm using Gaussian curve fitting reduces a total number of iterations as well as prevents divergence of searching the initial scanning position.

  90. Growth of an oscillating microbubble in an ultrasound field (Enhancement of rectified diffusion with a dual-frequency excitation method) Peer-reviewed

    Shin Yoshizawa, Shu Takagi, Yoichiro Matsumoto

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B　75　(752)　710-717　2009

    Publisher: Japan Society of Mechanical Engineers

    DOI： 10.1299/kikaib.75.752_710 　

    ISSN：0387-5016

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    Acoustic cavitation has an important role in ultrasound applications, such as HIFU (High Intensity Focused Ultrasound) therapy. Control of the growth of the cavitation bubbles is one of the important factors to control the effects of the cavitating bubbles. Several researchers have shown that a dual-frequency excitation method can enhance the growth of the bubbles due to rectified diffusion and consequently enhances the effects of the cavitation. In this study, the growth of an oscillating bubble in an ultrasound field due to the rectified diffusion is numerically investigated. In the model, we consider the compressibility of the surrounding liquid, mist generation inside the bubble, and the heat and mass transfer through the bubble interface. Mass transfer is calculated by solving the gas diffusion equation in liquid phase with the boundary condition at the bubble interface. The results reveal that the dual frequency excitation method can enhance the rectified diffusion in certain cases and it can be useful to control the growth of the cavitating bubbles.

  91. The Feed-Forward Controller of the Integrated System for Non-Invasive Ultrasound Diagnosis and Treatment Peer-reviewed

    N. Koizumi, K. Ota, D. Lee, S. Yoshizawa, A. Ito, Y. Kaneko, K. Yoshinaka, Y. Matsumoto, M. Mitsuishi

    J. Robotics Mechatronics　20　(1)　89-97　2008

  92. 4341 A Study on Technologizing and Digitalization of Skills in Medical Ultrasound Diagnosis and Therapy

    KOIZUMI Norihiro, OTA Kohei, LEE Deukhee, YOSHIZAWA Shin, ITOH Akira, NAGOSHI Mitsuru, HASHIZUME Hiroyuki, MATSUMOTO Yoichiro, MITSUISHI Mamoru

    The proceedings of the JSME annual meeting　2007　535-536　2007

    Publisher: The Japan Society of Mechanical Engineers

    DOI： 10.1299/jsmemecjo.2007.5.0_535 　

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    We have been studying the technologizing of skill of the medical doctor in the medical diagnosis and therapy. In this paper, we propose a method of decomposing and reconstructing required functions in medical ultrasound diagnosis and therapy.

  93. 4340 Real-time 3D tracking of kidney stones using ultrasound RF echo signals

    LEE Deukhee, KOIZUMI Norihiro, OTA Kohei, YOSHIZAWA Shin, ITOH Akira, MATSUMOTO Yoichiro, MITSUISHI Mamoru

    The proceedings of the JSME annual meeting　2007　533-534　2007

    Publisher: The Japan Society of Mechanical Engineers

    DOI： 10.1299/jsmemecjo.2007.5.0_533 　

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    For non-invasive 3D tracking of a target deep within a body, ultrasound-based visual servoing system is proposed. The ultrasound-based visual servoing system uses an ultrasound scanner for visual sensing. Two ultrasound probes equipped on the ultrasound scanner are located at the end-effector of a XYZ stage machine, and their scan planes parallel with XZ plane and YZ plane of the XYZ stage machine. The two sectional images of a target object in scan images of two ultrasound probes are registered as model images for pattern matching algorithm, respectively. 3D movement of the target object is sensed by pattern matching of the model images in input scan images. Displacement of the target between two successive frames decreases the accuracy of pattern matching. Therefore, scanning frame rate should be high enough to maintain the displacement of the target below threshold. Frame rate of ultrasound probes is adjustable through changing the view angle. Therefore, echo signals of ultrasound probes are used directly. Moreover, in order to save processing cost, image-based control method is used.

  94. Cloud cavitation control for lithotripsy using high intensity focused ultrasound Peer-reviewed

    Teiichiro Ikeda, Shin Yoshizawa, Masataka Tosaki, John S. Allen, Shu Takagi, Nobutaka Ohta, Tadaichi Kitamura, Yoichiro Matsumoto

    ULTRASOUND IN MEDICINE AND BIOLOGY　32　(9)　1383-1397　2006/09

    Publisher: ELSEVIER SCIENCE INC

    DOI： 10.1016/j.ultrasmedbio.2006.05.010 　

    ISSN：0301-5629

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    Cloud cavitation is potentially the most destructive form of cavitation. When the cloud cavitation is acoustically forced into a collapse, it has the potential to concentrate a very high pressure, more than 100 times the acoustic pressure, at its center. We experimentally investigate a method to control the collapse of high intensity focused ultrasound (HIFU)-induced cloud cavitation to fragment kidney stones. Our study examines a novel two-frequency wave designed to control the cloud cavitation (cavitation control [C-C] waveform); a high-frequency ultrasound pulse (I to 4 MHz) to create the cloud cavitation and a low-frequency trailing pulse (545 kHz) following the high-frequency pulse to force the cloud into collapse. High-speed photography has revealed that a localized distribution of the cloud cavitation can be produced within I mm on the solid surface by the high-frequency pulse. The low-frequency ultrasound was irradiated to the high-frequency-induced cloud cavitation. A subsequent shock wave emitted from the cloud cavitation was observed both in the shadowgraph photography and the remote hydrophone measurement. Furthermore, in vitro erosion tests of model and natural stones were conducted. In the case of model stones, the erosion rate of the C-C waveform showed a distinct advantage with the combined high- and low-frequency waves over either wave alone. Natural stones were eroded and most of the resulting fragments were less than I mm in diameter. The results show that the control of the cloud cavitation has untapped potential for the lithotripsy applications upon further optimization of the ultrasound parameters and complementary in vivo studies.

  95. Nonlinear behavior of the collapse of a spherical bubble cloud Peer-reviewed

    Yoshizawa, S, Ikeda, T, Takagi, S, Matsumoto, Y

    Transactions of the Japan Society of Mechanical Engineers　72　(3)　620-627　2006

    DOI： 10.1299/kikaib.72.620 　

  96. Medical ultrasound with microbubbles Peer-reviewed

    Y Matsumoto, JS Allen, S Yoshizawa, T Ikeda, Y Kaneko

    EXPERIMENTAL THERMAL AND FLUID SCIENCE　29　(3)　255-265　2005/03

    Publisher: ELSEVIER SCIENCE INC

    DOI： 10.1016/j.expthermflusci.2004.05.008 　

    ISSN：0894-1777

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    In the medical ultrasound applications, microbubbles are closely tied to the diagnostic/therapeutic uses. For diagnostic applications, their sound scattering properties yield improved imaging, when the microbubbles are used as contrast agents. the harmonics and subharmonics responses from the bubbles assist in distinguishing the acoustic scattering of blood from that of the surrounding tissue. The therapeutic use of microbubbles has recently been the subject of much interest. In a HIFU treatment, the heat generated by the bubble motion contributes an enhanced localized heating effect from the ultrasound. In the lithotripsy of renal calculi, the acoustic cloud cavitation contributes to the comminution of the renal stones. In all these applications, it is essential to understand the microbubbles and bubble cloud dynamics. The bubble motion and bubble cloud behaviour are strongly influenced by the internal phenomena of the bubbles, such as thermal diffusion, mist formation, mass diffusion and heat mass transfer through the bubble wall. In our research, bubble and bubble cloud dynamics in the medical ultrasound field have been examined. In this paper numeritation Control Lithotripsy (CCL), are highlighted. (C) 2004 Published by Elsevier Inc.

  97. Behaviour of a bubble cluster in an ultrasound field Peer-reviewed

    Y Matsumoto, S Yoshizawa

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS　47　(6-7)　591-601　2005/02

    Publisher: JOHN WILEY & SONS LTD

    DOI： 10.1002/fld.833 　

    ISSN：0271-2091

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    Ultrasound medical applications, such as an ultrasound imaging with micro-bubble contrast agents, and high intensity focused ultrasound (HIFU) therapy have attracted much attention in recent years. These applications have a close relation to the motion of micro-bubbles, so that it is essential to understand their dynamics. The bubble motion is influenced by the internal phenomena and its interaction with the surrounding medium, such as the thermal diffusion, the mist formation, the mass diffusion, the heat and mass transfer through the bubble wall. It is important that the oscillation of rnicro bubbles generates a strong acoustic pressure for these medical applications. The strong pressure also appears in the case of a bubble cluster, like a cloud cavitation. As these dynamics of bubbles are strongly influenced by the thermal phenomena inside them, it is necessary to construct the model taking these phenomena into account to analyse the behaviour of the bubble cluster precisely. Thus, the following effects are considered: the evaporation and condensation of the liquid at the bubble wall, the heat transfer through the bubble wall, and the compressibility of the liquid. Then the spherical bubble cluster is numerically simulated. When the frequency of the ultrasound is sufficiently high, the bubble cluster hardly oscillates. On the contrary, when the frequency of the ultrasound is at the resonance of the bubble cluster, the pressure wave generates the shock wave and it focuses to the cluster centre. As a result, the pressure inside the bubble at the cluster centre becomes much higher than that of a single bubble. Though this extreme high pressure causes the severe cavitation erosion, it is thought that this high energy concentration has the potential to be utilized for medical applications. Copyright (C) 2004 John Wiley Sons, Ltd.

  98. Renal stone comminution utilizing cloud cavitation erosion (1st report, the control of cloud cavitation) Peer-reviewed

    Teiichiro Ikeda, Shin Yoshizawa, Masataka Tosaki, Yukio Kaneko, Shu Takagi, Yoichiro Matsumoto

    Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B　70　(692)　904-911　2004

    Publisher: Japan Society of Mechanical Engineers

    DOI： 10.1299/kikaib.70.904 　

    ISSN：0387-5016

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    In a therapeutic ultrasound field, cavitation frequently forms a bubble cloud that consists of many microbubbles. A method to control the violent collapse of cloud cavitation is being developed. It is comprised of two frequency ultrasound forcing. The first is a higher frequency ultrasound waveform that makes cloud cavitation at the surface of the object. The second is a lower frequency waveform that produces a violent collapse of the cloud cavitation. If the phenomena is well controlled in time and space, it can be utilized for the stone crushing mechanism in lithotripsy. From a numerical simulation, the controllability of the cloud cavitation is predicted. A stable bubble cloud at the solid surface and the shock wave from the violent cloud cavitation collapse are observed by using a high-speed photography. The occurrence time of the collapsing phenomena of cloud cavitation is controlled within 100 ns and the area is controlled within several hundreds micrometers. Using the present method, stones are chipped away such that scoop-like indentations are achieved.

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Misc. 197

  1. High frequency ultrasound / photoacoustic imaging at Tohoku University

    西條芳文, 新楯諒, 鈴木陸, 石井琢郎, 荒川元孝, 梅村晋一郎, 吉澤晋, 長岡亮, 小林和人, 根本隆治

    超音波医学 Supplement　49　2022

    ISSN：1881-9311

  2. 切除不能膵癌に対する薬剤併用High intensity focused ultrasound(HIFU)治療

    祖父尼 淳, 村垣 善浩, 梅村 晋一郎, 岡本 淳, 吉澤 晋, 糸井 隆夫

    超音波医学　47　(Suppl.)　S325-S325　2020/11

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  3. 半球型アレイトランスデューサと4方向傾斜レーザ照射による3次元光音響イメージング

    森野 太介, 新楯 諒, 林 瑛己, 長岡 亮, 吉澤 晋, 梅村 晋一郎, 西條 芳文

    超音波医学　47　(Suppl.)　S524-S524　2020/11

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  4. Experimental Investigation of Relationship between Coagulation Size and Estimated Distribution of HIFU Heat Source from Displacement Distribution by Acoustic Radiation Force Imaging

    Hiroki Yabata, Shin Ichiro Umemura, Shin Yoshizawa

    IEEE International Ultrasonics Symposium, IUS　2020-September　2020/09/07

    DOI： 10.1109/IUS46767.2020.9251597 　

    ISSN：1948-5719

    eISSN：1948-5727

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    Accurate estimation of the ultrasonic heat source in advance of therapeutic ultrasound exposure is important to increase the safety and efficacy of high-intensity focused ultrasound (HIFU) treatment. Acoustic radiation force imaging using a HIFU short burst is expected as a procedure for such estimation from the distribution of tissue displacement. In this study, the relationship between the coagulation size and the distribution of the displacement measured by the technique was experimentally investigated by varying the depth of HIFU focal point from the surface of the target tissue and the HIFU exposure power. The result showed that the same amount of the displacement provided almost the same size of the coagulation. It suggests that the estimation method has a potential to enable the in-situ adjustment of HIFU power for appropriate treatment.

  5. Investigation on Ultrasonic Exposure Sequence by Luminol Sonochemiluminescence for Highly Effective Sonodynamic Treatment

    Kenk Tsukahara, Shin Ichiro Umemura, Shin Yoshizawa

    IEEE International Ultrasonics Symposium, IUS　2020-September　2020/09/07

    DOI： 10.1109/IUS46767.2020.9251776 　

    ISSN：1948-5719

    eISSN：1948-5727

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    Sonodynamic treatment (SDT) is a treatment modality for cancer, combining ultrasound, reactive oxygen species (ROS), and drug which enhances the generation of ROS. Although cancers can be noninvasively treated by SDT, it has a disadvantage of long treatment time. In this study, the effect of ultrasound sequences on the efficiency of ROS generation was investigated by using luminol sonochemiluminescence and high-speed photography of cavitation bubbles.

  6. Effect of alternate transmission of split apertures on bubble behavior and temperature rise for bubble-enhanced ultrasound treatment

    Sayaka Ito, Shin Ichiro Umemura, Shin Yoshizawa

    IEEE International Ultrasonics Symposium, IUS　2020-September　2020/09/07

    DOI： 10.1109/IUS46767.2020.9251407 　

    ISSN：1948-5719

    eISSN：1948-5727

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    In a cavitation-enhanced HIFU treatment, it is important to avoid generating bubbles larger than the resonance size through the coalescence of bubbles induced by the Bjerknes forces. In this study, the effect of the temporal change in pressure field to suppress the bubble coalescence at the nodes and antinodes in the pressure field was investigated by testing the effect of transmission alternating split apertures on the cavitation region and temperature rise.

  7. Three-dimensional photoacoustic imaging using a hemispherical array transducer and four way oblique laser irradiation

    森野太介, 新楯諒, 林瑛己, 長岡亮, 吉澤晋, 梅村晋一郎, 西條芳文

    超音波医学 Supplement　47　2020

    ISSN：1881-9311

  8. 高周波数帯域の光音響信号による細胞レベルのイメージング

    西條芳文, 新楯諒, 高橋爽, 平塚竜基, 石井琢郎, 吉澤晋, 梅村晋一郎, 長岡亮, 岩崎秀明, 伊田泰一郎

    乳腺甲状腺超音波医学　9　(4)　2020

    ISSN：2187-2880

  9. PDT・PDDの新応用・新技術 音響力学的療法によるがん治療 SDTはPDTを超えられるか

    小西 良幸, 堀瀬 友貴, 前田 真法, 岡本 淳, 生田 聡子, 岡本 芳晴, 石井 宏志, 吉澤 晋, 梅村 晋一朗, 祖父尼 淳, 正宗 賢, 伊関 洋, 西山 伸宏, 片岡 一則, 村垣 善浩

    日本レーザー医学会誌　40　(Suppl.)　S63-S63　2019/11

    Publisher: (NPO)日本レーザー医学会

    ISSN：0288-6200

    eISSN：1881-1639

  10. 光超音波トモグラフィにおける光超音波信号の初期位相の補正による深さ分解能の改善に関する研究 : 高空間分解能化を目指して (特集 超音波を使用した医療のあり方を探る(1))

    長岡 亮, 吉澤 晋, 梅村 晋一郎, 西條 芳文

    超音波techno　31　(3)　70-74　2019/05

    Publisher: 日本工業出版

    ISSN：0916-2410

  11. 高周波数アニュラアレイセンサによる被写界深度の拡大

    藤井佳祐, 佐藤泰, 菅野尚哉, 新楯諒, 小林和人, 吉澤晋, 梅村晋一郎, 西條芳文

    電子情報通信学会技術研究報告　119　(211(US2019 46-56))　2019

    ISSN：0913-5685

  12. Comparative study of one-way vertical illumination and four-way oblique illumination in three-dimensional photoacoustic imaging using a hemispherical array transducer

    森野太介, 新楯諒, 長岡亮, 吉澤晋, 梅村晋一郎, 西條芳文

    電子情報通信学会技術研究報告　119　(211(US2019 46-56))　2019

    ISSN：0913-5685

  13. Visualization of skin morphology and microcirculation with high frequency ultrasound and dual-wavelength photoacoustic microscope

    Yoshifumi Saijo, Taiichiro Ida, Hideaki Iwazaki, Jun Miyajima, Huabin Tang, Ryo Shintate, Kanta Sato, Tatsuki Hiratsuka, Shin Yoshizawa, Shinichiro Umemura

    Progress in Biomedical Optics and Imaging - Proceedings of SPIE　10878　2019

    DOI： 10.1117/12.2508599 　

    ISSN：1605-7422

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    Skin aging is characterized by color and wrinkle caused by degeneration of collagen and elastin in the dermis. Recently, the volume, diameter and branching of the micro vessels in the skin are proved to affect these biomechanical changes. Thus, high resolution imaging for both micro structure and micro vessels of the skin is desired. In the present study, dual-wavelength photoacoustic microscope (PAM) combined with high frequency ultrasound (HFUS) is developed to visualize both the morphology and microcirculation of the skin. Two Nd:YAG laser light sources with the wavelength of 532/556 nm, pulse width of 1.2/3.6 ns, pulse energy of 16 μJ/pulse and repetition rate of 1 kHz were equipped in the HFUS-PAM system. The optical fiber for laser delivery was inserted through the center hole of the concave ultrasound transducer with the central frequency of 75 MHz. Both HFUS and PA signals were acquired at the sampling rate of 500 MHz and the resolution of 12 bits. The transducer was scanned by voice coil actuators to obtain 3D dataset of HFUS and PA signals. Oxygen saturation of the micro circulation was calculated by the PA signals alternately obtained at 532 nm and 556 nm. 3D image of the layered structure and the micro vessels representing oxygen saturation in the 6 mm x 6 mm x 3 mm volume of the skin was successfully obtained with the system. HFUS-PAM will provide important information of skin morphology and microcirculation for assessment of skin aging.

  14. 切除不能難治癌に対する音響力学的療法の安全性に関する検討

    祖父尼 淳, 村垣 善浩, 藤田 充, 朝井 靖二, 伊関 洋, 正宗 賢, 岡本 淳, 小西 良幸, 堀瀬 友貴, 生田 聡子, 岸本 眞治, 泉 美喜雄, 吉澤 晋, 梅村 晋一郎, 糸井 隆夫

    日本消化器病学会雑誌　115　(臨増大会)　A806-A806　2018/10

    Publisher: (一財)日本消化器病学会

    ISSN：0446-6586

    eISSN：1349-7693

  15. 超音波治療の最前線-基礎と臨床- 切除不能難治癌に対する集束超音波(HIFU)治療と音響力学的治療(SDT)

    祖父尼 淳, 村垣 善浩, 佐野 隆友, 藤田 充, 朝井 靖二, 伊関 洋, 正宗 賢, 岡本 淳, 小西 良幸, 堀瀬 友貴, 生田 聡子, 岸本 眞治, 泉 美喜雄, 吉澤 晋, 梅村 晋一郎, 糸井 隆夫

    Thermal Medicine　34　(Suppl.)　67-67　2018/08

    Publisher: (一社)日本ハイパーサーミア学会

    ISSN：1882-2576

  16. 集束超音波治療(FUS)の最前線 集束超音波とドラッグデリバリーシステムを組み合わせた音響力学的療法の基礎と臨床試験

    村垣 善浩, 小西 良幸, 堀瀬 友貴, 岡本 淳, 吉澤 晋, 岡本 芳晴, 祖父尼 淳, 西山 伸宏, 片岡 一則, 正宗 賢

    Neurosonology　31　(増刊)　52-52　2018/06

    Publisher: (一社)日本脳神経超音波学会

    ISSN：0917-074X

  17. 焦点ナビゲーション法のHIFU治療への応用

    瀬尾 晃平, 市塚 清健, イズデプスキ 龍也, 西井 彰悟, 土肥 聡, 岩崎 亮祐, 高木 亮, 吉澤 晋, 梅村 晋一郎, 関沢 明彦

    超音波医学　45　(Suppl.)　S560-S560　2018/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  18. HIFU照射方式の違いによるブタ腎実質焼灼の比較検証

    イズデプスキ 龍也, 瀬尾 晃平, 西井 彰悟, 土肥 聡, 高木 亮, 吉澤 晋, 梅村 晋一郎, 関沢 明彦, 市塚 清健

    超音波医学　45　(Suppl.)　S709-S709　2018/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  19. 皮膚熱傷を低減させるためのHIFU照射プロトコールの検証

    西井 彰悟, 瀬尾 晃平, イズデプスキ 龍也, 土肥 聡, 岩崎 亮祐, 高木 亮, 吉沢 晋, 梅村 晋一郎, 関沢 明彦, 市塚 清健

    超音波医学　45　(Suppl.)　S709-S709　2018/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  20. 超音波によるtheranostics(診断と治療)の広がり 音響力学的療法におけるセラノスティクス

    村垣 善浩, 小西 良幸, 吉澤 晋, 岡本 芳晴, 祖父尼 淳, 玉野 聡, 植山 剛, 竹前 和久, 西山 伸宏, 片岡 一則

    超音波医学　45　(Suppl.)　S186-S186　2018/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

  21. 超音波によるtheranostics(診断と治療)の広がり 切除不能難治癌に対する集束超音波治療と音響力学的治療

    祖父尼 淳, 村垣 善浩, 藤田 充, 朝井 靖二, 岡本 淳, 小西 良幸, 堀瀬 友貴, 吉澤 晋, 梅村 晋一郎, 糸井 隆夫

    超音波医学　45　(Suppl.)　S186-S186　2018/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

  22. 音響力学的療法によるがん治療

    岡本 淳, 村垣 善浩, 正宗 賢, 伊関 洋, 小西 良幸, 堀瀬 友貴, 清水 京子, 糸井 隆夫, 祖父尼 淳, 梅村 晋一郎, 吉澤 晋, 高木 亨, 岡本 芳晴, 玉野 聡, 植山 剛, 竹前 和久

    未来医学　(31)　73-78　2018/02/15

    Publisher: (一社)未来医学研究会

    DOI： 10.20780/00031872 　

    ISSN：0910-9870

  23. Basic study on ultrasonic tissue monitoring using 1.5-dimensional ultrasound phased array for ultrasound-guided high intensity focused ultrasound treatment Peer-reviewed

    Ryo Takagi, Shin Yoshizawa, Shin Ichiro Umemura

    IEEE International Ultrasonics Symposium, IUS　2017/10/31

    Publisher: IEEE Computer Society

    DOI： 10.1109/ULTSYM.2017.8092624 　

    ISSN：1948-5719

    eISSN：1948-5727

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    In conventional ultrasonic monitoring of high intensity focused ultrasound (HIFU) treatment, it has been difficult to track the target region when the tissue to be treated deviates from the imaging plane along the elevation axis of the 1-D probe. A 2-D phased array probe providing 3-D imaging capability requires a large number of elements and it is very expensive to build a system to drive all channels simultaneously. A 1.5-D phased array probe can provide a good compromise between conventional 1-D and 2-D phased array probes and has significant cost and implementation advantages. In this study, a new 1.5-D phased array probe consisting of 64×4 elements was designed and developed to track tissue motion within mm order along the elevation direction and the elevational displacement range where the tissue tracking is effective was investigated.

  24. Three dimensional pressure field measurement of focused ultrasound by optical phase contrast method Peer-reviewed

    Shin Yoshizawa, Takuya Nakamura, Yohei Sasaki, Maxime Lafond, Shin Ichiro Umemura

    IEEE International Ultrasonics Symposium, IUS　2017/10/31

    Publisher: IEEE Computer Society

    DOI： 10.1109/ULTSYM.2017.8091908 　

    ISSN：1948-5719

    eISSN：1948-5727

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    A hydrophone scanning method is gold standard for the ultrasound filed measurement. However, the hydrophone scanning is time consuming especially for the three-dimensional measurement. On the other hand, two-dimensional data can be acquired simultaneously by an optical measurement method using a camera. In this study, the optical phase contrast method was used to measure a three-dimensional pressure filed generated by a focused transducer.

  25. Prediction of thermal coagulation by short-pulse pre-exposure for cavitation-enhanced ultrasonic heating Peer-reviewed

    Ryosuke Iwasaki, Ryo Takagi, Shin Yoshizawa, Shin Ichiro Umemura

    IEEE International Ultrasonics Symposium, IUS　2017/10/31

    Publisher: IEEE Computer Society

    DOI： 10.1109/ULTSYM.2017.8092354 　

    ISSN：1948-5719

    eISSN：1948-5727

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    Targeting the ultrasound beam and predicting the thermal coagulation in advance are important for high-intensity focused ultrasound (HIFU) treatment. Cavitation bubbles are known to enhance ultrasonic heating, however, temporal and spatial control of their generation is not simple. In our previous study, a method utilizing acoustic radiation force to predict thermal coagulation was suggested. In this study, it was investigated whether the proposed method works effectively even for the cavitation-enhanced ultrasonic heating and can be used to ensure both safety and efficiency of the treatment.

  26. Visualization of the microcirculation in micro vasculatures by photoacoustic tomography with high frequency spherical array transducer Peer-reviewed

    Ryo Nagaoka, Takuya Tabata, Ryo Takagi, Shin Yoshizawa, Shin Ichiro Umemura, Yoshifumi Saijo

    IEEE International Ultrasonics Symposium, IUS　2017/10/31

    Publisher: IEEE Computer Society

    DOI： 10.1109/ULTSYM.2017.8092091 　

    ISSN：1948-5719

    eISSN：1948-5727

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    A spatial resolution of photoacoustic tomography (PAT) has been limited by the receive frequency significantly lower than that of photoacoustic microscopy. In the present study, an in vivo microcirculation is visualized by a PAT system by using a newly developed spherical array transducer with a center frequency of 10 MHz. Additionally, we propose a novel reconstruction method suppressing the side lobe level with Wiener filtering.

  27. Differentiation of vein and lymphatic vessel by photoacoustic imaging system with parabolic array transducer and tunable laser Peer-reviewed

    Takuya Tabata, Ryo Nagaoka, Shin Yoshizawa, Shin Ichiro Umernura, Yoshifumi Saijo

    IEEE International Ultrasonics Symposium, IUS　2017/10/31

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2017.8091669 　

    ISSN：1948-5719

    eISSN：1948-5727

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    Recently, much attention is being paid to lymphatic circulation because intralymphatic immunotherapy and chemotherapy achieved significant clinical benefits. However, conventional ultrasound or photoacoustic (PA) imaging is hard to visualize lymphatic vessels. The objective of the present study is to visualize lymphatic vessels administrated with photoacoustic contrast agents by PA imaging system based on a tunable laser setup.

  28. Effect of HIFU exposure method to suppress standing waves on cavitation generation

    117　(227)　33-37　2017/10/05

    Publisher: 電子情報通信学会

    ISSN：0913-5685

  29. 進化する超音波治療技術の最前線 2)キャビテーション援用超音波加熱におけるワイドビーム超音波照射の加熱凝固領域に対する影響=超音波伝播の非線形性による超音波加熱増強効果を低減する=

    吉澤晋, 梅村晋一郎

    超音波Techno　29　(5)　62-67　2017/09

    Publisher: 日本工業出版

    ISSN：0916-2410

  30. TRAPシーケンスにおける低侵襲胎児治療に対する第二世代HIFUシステムの評価

    瀬尾 晃平, 市塚 清健, 岡井 崇, 仲村 将光, 長谷川 潤一, 松岡 隆, 北代 祐三, 住江 正大, 月森 清巳, 吉澤 晋, 梅村 晋一郎, 関沢 明彦

    昭和学士会雑誌　77　(2)　241-241　2017/04

    Publisher: 昭和大学学士会

    ISSN：2187-719X

    eISSN：2188-529X

  31. HIFUの臨床応用 HIFUによる胎児治療

    市塚 清健, 瀬尾 晃平, 松岡 隆, 仲村 将光, 高木 亮, 吉澤 晋, 梅村 晋一郎, 岡井 崇

    超音波医学　44　(Suppl.)　S179-S179　2017/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  32. HIFUを用いたTRAP sequenceに対する胎児治療の成績と今後の課題

    瀬尾 晃平, 市塚 清健, 岡井 崇, 松岡 隆, 高木 亮, 吉澤 晋, 梅村 晋一郎, 関沢 明彦

    超音波医学　44　(Suppl.)　S579-S579　2017/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  33. Quantitative Measurement of Pulsed Ultrasonic Pressure Field using Optical Phase Contrast Method and Acoustic Holography

    116　(419)　5-10　2017/01/25

    Publisher: 電子情報通信学会

    ISSN：0913-5685

  34. Effectiveness of High-Speed Imaging on Predicting Thermal Coagulation Utilizing Acoustic Radiation Force by Pulsed High-Intensity Focused Ultrasound

    116　(419)　11-15　2017/01/25

    Publisher: 電子情報通信学会

    ISSN：0913-5685

  35. Development in Method to Reduce Temperature Rise near Tissue Boundary in Cavitation-Enhanced High-Intensity Focused Ultrasound Treatment

    116　(419)　17-21　2017/01/25

    Publisher: 電子情報通信学会

    ISSN：0913-5685

  36. Study of Simulation of Optical Propagation for Phase Retrieval in Shadowgraph of Ultrasound Field

    116　(241)　23-27　2016/10/07

    Publisher: 電子情報通信学会

    ISSN：0913-5685

  37. Study on Control of Coagulation Size Induced by Bubble-Enhanced Ultrasound Heating Using Scattered Ultrasound Signal from Focal Region of Therapeutic Ultrasound

    116　(241)　11-15　2016/10/07

    Publisher: 電子情報通信学会

    ISSN：0913-5685

  38. Analysis of cavitation bubbles generated by high-intensity focused ultrasound in biological tissue using high-speed optical and acoustic imaging

    116　(241)　17-22　2016/10/07

    Publisher: 電子情報通信学会

    ISSN：0913-5685

  39. ―音響に関する施設と装置―強力集束超音波装置(医用超音波装置)

    吉澤晋

    日本音響学会誌　72　(9)　576‐577　2016/09/01

    DOI： 10.20697/jasj.72.9_576 　

    ISSN：0369-4232

  40. 先進医療に寄与する超音波技術 頸動脈壁の粘弾性計測に関する検討=生体由来の拍動微小変位の速度分散を用いて=

    長岡亮, 荒川元孝, 吉澤晋, 梅村晋一郎, 西條芳文, 小林和人

    超音波Techno　28　(3)　10‐14　2016/06/01

    ISSN：0916-2410

  41. 先進医療に寄与する超音波技術 強力集束超音波治療の組織変化モニタリング=高速超音波イメージングによる非相関モニタリング=

    吉澤晋, 佐々木翔也, 高木亮, 梅村晋一郎

    超音波Techno　28　(3)　39‐42　2016/06/01

    ISSN：0916-2410

  42. 先進医療に寄与する超音波技術 強力集束超音波治療のモニター時における治療用超音波ノイズの除去

    高木亮, 吉澤晋, 梅村晋一郎

    超音波Techno　28　(3)　1‐5　2016/06/01

    ISSN：0916-2410

  43. 超音波治療の臨床応用最前線 HIFUによる胎児治療

    市塚 清健, 瀬尾 晃平, 青木 弘子, 松岡 隆, 長谷川 潤一, 石川 哲也, 岡井 崇, 吉澤 晋, 梅村 晋一郎

    超音波医学　43　(Suppl.)　S238-S238　2016/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  44. HIFUにおける焦点のナビゲーション及びキャビテーションの可視化に関する基礎研究

    瀬尾 晃平, 市塚 清健, 吉澤 晋, 梅村 晋一郎, 仲村 将光, 長谷川 潤一, 松岡 隆, 関沢 明彦, 岡井 崇

    超音波医学　43　(Suppl.)　S713-S713　2016/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

    eISSN：1881-9311

  45. 超音波治療の効果判定とその臨床経過観察 癌に対する薬剤併用集束超音波治療(Application of Therapeutic Ultrasound and Monitoring Its Clinical Outcome High intensity therapeutic ultrasound combined with drug for cancer patients)

    村垣 善浩, 前田 真法, 伊関 洋, 岡本 淳, 岸本 眞治, 正宗 賢, 高木 亮, 吉澤 晋, 梅村 晋一郎

    超音波医学　43　(Suppl.)　S217-S217　2016/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

  46. 気泡援用集束超音波治療の安全性向上に関する研究

    坂本 和広, 高木 亮, 吉澤 晋, 梅村 晋一郎

    電気関係学会東北支部連合大会講演論文集　2016　189-189　2016

    Publisher: 電気関係学会東北支部連合大会実行委員会

    DOI： 10.11528/tsjc.2016.0_189 　

  47. 音響キャビテーションによる活性酸素生成における超音波焦点走査の影響

    西高 慎也, 高木 亮, 吉澤 晋, 梅村 晋一郎

    電気関係学会東北支部連合大会講演論文集　2016　187-187　2016

    Publisher: 電気関係学会東北支部連合大会実行委員会

    DOI： 10.11528/tsjc.2016.0_187 　

  48. 光学的測定と音響ホログラフィー解析による高強度超音波音場の定量測定

    中村 拓也, 大山 誠司, 花山 洋貴, 高木 亮, 吉澤 晋, 梅村 晋一郎

    電気関係学会東北支部連合大会講演論文集　2016　178-178　2016

    Publisher: 電気関係学会東北支部連合大会実行委員会

    DOI： 10.11528/tsjc.2016.0_178 　

  49. Focal zone visualization by absorption imaging method to predict thermal lesion formation in ultrasonic thermal therapy

    Tohoku-Section Joint Convention Record of Institutes of Electrical and Information Engineers, Japan　2016　25-25　2016

    Publisher: Organizing Committee of Tohoku-Section Joint Convention of Institutes of Electrical and Information Engineers, Japan

    DOI： 10.11528/tsjc.2016.0_25 　

  50. Focused Ultrasound and Lithotripsy Peer-reviewed

    Teiichiro Ikeda, Shin Yoshizawa, Norihiro Koizumi, Mamoru Mitsuishi, Yoichiro Matsumoto

    THERAPEUTIC ULTRASOUND　880　113-129　2016

    Publisher: SPRINGER INT PUBLISHING AG

    DOI： 10.1007/978-3-319-22536-4_7 　

    ISSN：0065-2598

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    Shock wave lithotripsy has generally been a first choice for kidney stone removal. The shock wave lithotripter uses an order of microsecond pulse durations and up to a 100 MPa pressure spike triggered at approximately 0.5-2 Hz to fragment kidney stones through mechanical mechanisms. One important mechanism is cavitation. We proposed an alternative type of lithotripsy method that maximizes cavitation activity to disintegrate kidney stones using high-intensity focused ultrasound (HIFU). Here we outline the method according to the previously published literature (Matsumoto et al., Dynamics of bubble cloud in focused ultrasound. Proceedings of the second international symposium on therapeutic ultrasound, pp 290-299, 2002; Ikeda et al., Ultrasound Med Biol 32: 1383-397, 2006; Yoshizawa et al., Med Biol Eng Comput 47: 851-860, 2009; Koizumi et al., A control framework for the non-invasive ultrasound the ragnostic system. Proceedings of 2009 IEEE/RSJ International Conference on Intelligent Robotics and Systems (IROS), pp 4511-4516, 2009; Koizumi et al., IEEE Trans Robot 25: 522-538, 2009). Cavitation activity is highly unpredictable; thus, a precise control system is needed. The proposed method comprises three steps of control in kidney stone treatment. The first step is control of localized high pressure fluctuation on the stone. The second step is monitoring of cavitation activity and giving feedback on the optimized ultrasound conditions. The third step is stone tracking and precise ultrasound focusing on the stone. For the high pressure control we designed a two-frequency wave (cavitation control (C-C) waveform); a high frequency ultrasound pulse (1-4 MHz) to create a cavitation cloud, and a low frequency trailing pulse (0.5 MHz) following the high frequency pulse to force the cloud into collapse. High speed photography showed cavitation collapse on a kidney stone and shock wave emission from the cloud. We also conducted in-vitro erosion tests of model and natural kidney stones. For the model stones, the erosion rate of the C-C waveform showed a distinct advantage with the combined high and low frequency waves over either wave alone. For optimization of the high frequency ultrasound intensity, we investigated the relationship between sub-harmonic emission from cavitation bubbles and stone erosion volume. For stone tracking we have also developed a non-invasive ultrasound theragnostic system (NIUTS) that compensates for kidney motion. Natural stones were eroded and most of the resulting fragments were less than 1 mm in diameter. The small fragments were small enough to pass through the urethra. The results demonstrate that, with the precise control of cavitation activity, focused ultrasound has the potential to be used to develop a less invasive and more controllable lithotripsy system.

  51. A Study of the driving circuit for array transducer considering its impedance properties Peer-reviewed

    Hayato Jimbo, Kota Goto, Shin Yoshizawa, Shin Ichiro Umemura

    2015 IEEE International Ultrasonics Symposium, IUS 2015　7329179　2015/11/13

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2015.0429 　

    ISSN：1948-5719

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    A multi-channel array transducer can enlarge the treatment volume of HIFU (High-Intensity Focused Ultrasound), which is a noninvasive method for cancer therapy, by generating and scanning multiple foci. In our previous study, we developed a compact and highly efficient driving circuit using staircase wave voltage for typical single HIFU transducer that the impedance is almost real at the resonance frequency. However, an array transducer element can have too capacitive impedance that affects the output voltage waveform designed for reducing the harmonics components. To solve this problem, we propose a new circuit to drive an array transducer considering its imaginary impedance. The proposed circuit was able to reduce not only the odd harmonics but also electrical power consumption. Simulation of the relationship between the number of staircase wave steps and the power consumption proved that the total power consumption due to intentional turn-on decreased in proportion to the number of steps.

  52. Efficient generation of reactive oxygen species sonochemically generated by cavitation bubbles Peer-reviewed

    Jun Yasuda, Shin Yoshizawa, Shin Ichiro Umemura

    2015 IEEE International Ultrasonics Symposium, IUS 2015　7329535　2015/11/13

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2015.0402 　

    ISSN：1948-5719

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    Background: Sonodynamic treatment is a cancer treatment method using by cavitation bubbles generated by ultrasound. In sonodynamic treatment, generating ROS efficiently by cavitation bubbles at target cancerous tissue is important. Objective: The aim of this paper is generating ROS efficiently by using exposure sequence which have short, high-intensity ultrasound pulse (triggered pulse) immediate followed by long, moderately low-intensity ultrasound burst (sustaining waves). Experiment: Cavitation bubbles were generated by using two sequences. The firsts sequence had both of triggered pulse and sustaining waves. The second one had only triggered pulse. After ultrasound exposure finished, the amount of ROS was quantified by KI method. Result and conclusion: The sequence which had both trigger pulse and sustaining waves generated ROS more efficient than the sequence which had only triggered pulse. The reason of this result is that sustaining waves oscillated cavitation bubbles volumetrically which were generated by triggered pulse and such volume oscillation of bubbles by sustaining waves contributes for efficient generation of ROS.

  53. Quantitative measurement of pulsed ultrasound pressure field using optical phase contrast Peer-reviewed

    Seiji Oyama, Mohd Syahid, Jun Yasuda, Shin Yoshizawa, Shin Ichiro Umemura

    2015 IEEE International Ultrasonics Symposium, IUS 2015　7329280　2015/11/13

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2015.0228 　

    ISSN：1948-5719

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    The most common method to measure an ultrasound pressure field, hydrophone scanning, requires a long scanning time and potentially disturbs the field, This may limit the efficiency in development of ultrasonic application in medicine. In this study, an optical phase contrast method, enabling the fast and noninterfering measurement, is proposed. This method measures the modulated phase of light caused by the focused ultrasound pulse pressure field. Then, a CT algorithm to quantitatively reconstruct the 3D pressure field is applied. The result agreed well with the measurement by a hydrophone.

  54. Study of ultrasound transducer which produces second harmonic superimposed signal Peer-reviewed

    Zulfadhli Zaini, Shin Ichiro Umemura, Hayato Jimbo, Ryo Takagi, Shin Yoshizawa

    2015 IEEE International Ultrasonics Symposium, IUS 2015　7329298　2015/11/13

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2015.0555 　

    ISSN：1948-5719

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    Cavitation is the formation of gas cavities in a liquid, in the consequence of rarefactional pressure acting upon the liquid. Producing such negative pressure exceeding the cavitation threshold in a travelling wave mode is hard to achieve due to nonlinear propagation followed by focal phase shift. Superimposing the second harmonic to fundamental is an alternative way to solve the problem while able to efficiently form and control the cavitation bubbles which expedite the treatment with high intensity focused ultrasound (HIFU). However, an air-backed transducer in conventional design is not suitable to generate both the second harmonic and fundamental at the same time. In order to overcome this problem, we propose a high impedance matching layer approach. We further explore the possibility of a double matching layer design with an additional lighter layer, to increase the performance of the transducer. Numerical simulation and experimental measurement have shown that by using high impedance matching layer, efficiently generating both the second harmonic (2 MHz) and fundamental (1 MHz) at the same time is possible. Numerical simulation also showed that further study is needed for the double matching layer approach to significant improve the performance.

  55. Monitoring of lesions induced by cavitation-enhanced high-intensity focused ultrasound using shear wave elastography Peer-reviewed

    Ryosuke Iwasaki, Ryo Nagaoka, Yoshifumi Saijo, Shin Ichiro Umemura, Ryo Takagi, Hayato Jimbo, Shin Yoshizawa

    2015 IEEE International Ultrasonics Symposium, IUS 2015　7329182　2015/11/13

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2015.0042 　

    ISSN：1948-5719

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    Shear wave elastography is expected as a noninvasive monitoring method in high-intensity focused ultrasound treatment. Since elastography is usually applied to detect a lesion near a superficial layer, it is challenging to induce and propagate shear waves in deep tissue. Acoustic cavitation bubbles have the potential to promote the efficiency of the treatment; however the presence of remaining microbubbles may interfere with the shear wave propagation and make the detection of the accompanying displacements difficult. In this paper, it is examined whether the detection of the region where increased shear wave propagation velocity in ex vivo tissue is possible even in the presence of microbubbles and 'HIFU push' shear wave elastography has the advantage in terms of shear wave induction in deep tissue compared with a conventional technique by irradiating push beams from the same therapeutic transducer as HIFU exposure.

  56. 1P5-7 Study on Heavy Matching Layer Transducer Towards Producing Second Harmonic.

    Zulfadhli Zaini, Osuga Masamizu, Jimbo Hayato, Yasuda Jun, Takagi Ryo, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　36　"1P5-7-1"-"1P5-7-2"　2015/11/05

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  57. 1P5-11 Monitoring of High-Intensity Focused Ultrasound Treatment Using Shear Wave Elastography Induced by 2D Array Therapeutic Transducer

    Iwasaki Ryosuke, Takagi Ryo, Nagaoka Ryo, Jimbo Hayato, Yoshizawa Shin, Saijo Yoshifumi, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　36　"1P5-11-1"-"1P5-11-2"　2015/11/05

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  58. 2E2-3 Real-time Treatment Feedback Using Novel Filter for Eliminating Therapeutic Ultrasound Noise in US-guided High-Intensity Focused Ultrasound Treatment

    Takagi Ryo, Jimbo Hayato, Iwasaki Ryosuke, Tomiyasu Kentaro, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　36　"2E2-3-1"-"2E2-3-2"　2015/11/05

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  59. 2P5-4 Efficient Generation of Cavitation Bubbles and Reactive Oxygen Species using Triggered HIFU Sequence for Sonodynamic Treatment

    Yasuda Jun, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　36　"2P5-4-1"-"2P5-4-2"　2015/11/05

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  60. 3J1-3 Quantitative Measurement of Ultrasound Pressure Field by Optical Phase Contrast Method and Acoustic Holography

    Oyama Seiji, Yasuda Jun, Hanayama Hiroki, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　36　"3J1-3-1"-"3J1-3-2"　2015/11/05

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  61. 2P5-3 Advantage of Annular Focal Region Generated by Sector-Vortex Array in Cavitation-Enhanced High-Intensity Focused Ultrasound Treatment

    Jimbo Hayato, Takagi Ryo, Goto Kota, Taguchi Kei, Yoshizawa Shin, Umemura Shinichiro

    Proceedings of Symposium on Ultrasonic Electronics　36　"2P5-3-1"-"2P5-3-2"　2015/11/05

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  62. 2P5-7 Study of Cavitation Behavior during High-Intensity Focused Ultrasound Exposure by Using Flash Imaging

    Taguchi Kei, Takagi Ryo, Yasuda Jun, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　36　"2P5-7-1"-"2P5-7-2"　2015/11/05

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  63. Intrinsic elastography and its dependence on arterial flow volume Peer-reviewed

    Ryo Nagaoka, Kazuto Kobayashi, Shin Yoshizawa, Shin Ichiro Umemura, Yoshifumi Saijo

    Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS　2015-November　6309-6312　2015/11/04

    Publisher: IEEE

    DOI： 10.1109/EMBC.2015.7319835 　

    ISSN：1557-170X

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    We propose a new estimation method of tissues stiffness from deformation induced by arterial pulsation. The new method was named Intrinsic Elastography (IE). Under two assumptions that the deformation induced by pulsation propagates throughout the body, and the propagation velocity (PV) is closely related to the mechanical properties of tissues, the IE can evaluate the tissue stiffness based on the PV. However, this method has an issue that the observed PVs change with the changes of amounts of the flow. In this paper, we propose the new estimation method in order to estimate true shear elasticity in spite of the changes. The results was compared to the results of SWI. The results was almost identical to the result of SWI, or showed the similar results.

  64. Quantitative assessment of reactive oxygen species generation by cavitation incepted efficiently using nonlinear propagation effect Peer-reviewed

    Jun Yasuda, Shin Yoshizawa, Shin Ichiro Umemura

    AIP Conference Proceedings　1685　040003　2015/10/28

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.4934398 　

    ISSN：0094-243X

    eISSN：1551-7616

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    Sonodynamic treatment is a treatment method that uses chemical bio-effect of cavitation bubbles. Reactive oxygen species that can kill cancerous tissue is induced by such chemical effect of cavitation bubbles and it is important to generate them efficiently for effective sonodynamic treatment. Cavitation cloud can be formed by an effect of nonlinear propagation and focus and in this study, it was experimentally investigated if cavitation cloud was useful for efficient generation of reactive oxygen species. As a result, it was demonstrated that cavitation cloud would be useful for efficient generation of reactive oxygen species.

  65. 医工連携と癌治療 国産DDS製剤と集束超音波治療装置による音響力学的療法の実現

    村垣 善浩, 前田 真法, 伊関 洋, 岡本 淳, 岸本 眞治, 正宗 賢, 吉澤 晋, 梅村 晋一郎

    日本癌治療学会誌　50　(2)　447-448　2015/09

    Publisher: (一社)日本癌治療学会

    ISSN：0021-4671

  66. A Study of the Driving Circuit for Array Transducer Considering the Impedance Properties

    JIMBO Hayato, GOTO Kota, YOSHIZAWA Shin, UMEMURA Shinnichiro

    Technical report of IEICE. EA　114　(423)　39-43　2015/01/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    High-intensity focused ultrasound (HIFU) is a noninvasive method for cancer treatments, and one of the requirements for clinical use is to make the treatment more efficient. One of the approach, there is a multi-channel array transducer to enlarge treatment volume by making multiple focal points and scanning focal points. Since array transducer needs driving circuits for each channel, we have developed studying compact and high-efficiency driving circuits. In this study, we designed and made a driving circuit for array transducers considering the impedance properties. We compared new circuit and prior circuit by simulating its electrical power consumption and measuring focal pressure.

  67. Quantitative Measurement of Pulsed Ultrasound Pressure Field Using Optical Phase Contrast

    OYAMA Seiji, SYAHID Mohd, YASUDA Jun, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    Technical report of IEICE. EA　114　(423)　69-74　2015/01/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    Establishment of fast and accurate measurement of ultrasound pressure field leads to the development of ultrasound application in medication. The most common method is a hydrophone scan which requires a long scanning time and disturbs the acoustic field. In this study, we used an optical phase contrast method for the measurement which enables a fast and noninterfering measurement. This method measures the modulated phase of light cause by the pulsed ultrasound pressure field. Then, we applied a CT algorithm to reconstruct the 3D ultrasound pressure field and measure the pressure field quantitatively. The result of optical phase contrast method was compared with that of hydrophone measurement and simulation and well agreement was achieved.

  68. Monitoring of Cavitation Bubbles Induced by High-Intensity Focused Ultrasound in a Graphite Gel Phantom

    TAGUCHI Kei, TAKAGI Ryo, YASUDA Jun, MIYASHITA Takuya, OYAMA Seiji, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    IEICE technical report. Ultrasonics　114　(422)　63-68　2015/01/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    High-intensity focused ultrasound (HIFU) treatment is a noninvasive treatment method in which ultrasound is focused to a target tissue such as cancer to be thermally coagulated. Cavitation bubbles can be used to provide efficient therapy. In this case, it is necessary to monitor cavitation bubbles. In this study, we examined the efficiency of high-speed pulse inversion imaging with plane wave transmission for monitoring cavitaion bubbles. Cavitation bubbles were generated and monitored by ultrasound imaging and high-speed photography in a graphite gel phantom. The result suggests that pulse inversion imaging is efficient when duration of bubble vibration is short after cavitation phenomenon.

  69. Quantitative Measurement of Pulsed Ultrasound Pressure Field Using Optical Phase Contrast

    OYAMA Seiji, SYAHID Mohd, YASUDA Jun, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    IEICE technical report. Ultrasonics　114　(422)　105-110　2015/01/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    Establishment of fast and accurate measurement of ultrasound pressure field leads to the development of ultrasound application in medication. The most common method is a hydrophone scan which requires a long scanning time and disturbs the acoustic field. In this study, we used an optical phase contrast method for the measurement which enables a fast and noninterfering measurement. This method measures the modulated phase of light cause by the pulsed ultrasound pressure field. Then, we applied a CT algorithm to reconstruct the 3D ultrasound pressure field and measure the pressure field quantitatively. The result of optical phase contrast method was compared with that of hydrophone measurement and simulation and well agreement was achieved.

  70. A Study of the Driving Circuit for Array Transducer Considering the Impedance Properties

    JIMBO Hayato, GOTO Kota, YOSHIZAWA Shin, UMEMURA Shinnichiro

    IEICE technical report. Ultrasonics　114　(422)　75-79　2015/01/28

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    High-intensity focused ultrasound (HIFU) is a noninvasive method for cancer treatments, and one of the requirements for clinical use is to make the treatment more efficient. One of the approach, there is a multi-channel array transducer to enlarge treatment volume by making multiple focal points and scanning focal points. Since array transducer needs driving circuits for each channel, we have developed studying compact and high-efficiency driving circuits. In this study, we designed and made a driving circuit for array transducers considering the impedance properties. We compared new circuit and prior circuit by simulating its electrical power consumption and measuring focal pressure.

  71. 2P5-3 Analysis of Ultrasound-Enhanced Heating in near and far Vicinity of Cavitation Area(Poster Session)

    Miyashita Takuya, Yasuda Jun, Taguchi Kei, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　35　309-310　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  72. 2P5-10 Detection of Thermally-Induced Lesion Using Shear Wave Imaging in Cavitation-Enhanced High-Intensity Focused Ultrasound Therapy(Poster Session)

    Iwasaki Ryosuke, Nagaoka Ryo, Takagi Ryo, Goto Kota, Yoshizawa Shin, Saijo Yoshifumi, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　35　323-324　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  73. 3J3-2 Elimination of Therapeutic Ultrasound Noise from Pre-beamformed RF Data in Ultrasound Imaging for US-guided High-Intensity Focused Ultrasound Treatment(Biomedical Ultrasound III)

    Takagi Ryo, Goto Kota, Jinbo Hayato, Matsuura Keiko, Iwasaki Ryosuke, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　35　393-394　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  74. 2P5-2 Analysis of Decorrelation in Ultrasonic Echo Signals Coincided with Tissue Change due to High-Intensity Focused Ultrasound Enhanced by Cavitation(Poster Session)

    Matsuura Keiko, Takagi Ryo, Yanagisawa Yukari, Yoshizawa Shin, Kodama Tetsuya, Umemura Shim-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　35　307-308　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  75. 2P5-1 Effect of Controlled Offset of Focal Position in Cavitation Enhanced High Intensity Focused Ultrasound Treatment(Poster Session)

    Goto Kota, Takagi Ryo, Jinbo Hayato, Miyashita Takuya, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　35　305-306　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  76. 3P5-19 A Basic Study of Intrinsic Elastography Based on Propagation Velocity Distribution Induced by Artery Pulsation(Poster Session)

    Nagaoka Ryo, Iwasaki Ryosuke, Arakawa Mototaka, Kobayashi Kazuto, Yoshizawa Shin, Umemura Shin-ichiro, Saijo Yoshifumi

    Proceedings of Symposium on Ultrasonic Electronics　35　545-546　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  77. 1P5-22 Quantitative Assessment of Reactive Oxygen Sonochemically Generated by Cavitation Bubbles(Poster Session)

    Yasuda Jun, Miyashita Takuya, Taguchi Kei, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　35　167-168　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  78. 2E2-4 Quantitative Measurement of High Intensity Focused Ultrasound Pressure Field by Optical Phase Contrast Method Applying Non-Continuous Phase Unwrapping Algorithm(Biomedical Ultrasound I)

    Syahid Mohd, Oyama Seiji, Yasuda Jun, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　35　197-198　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  79. A Basic Study of Visualization of Propagation Velocity Distribution Induced by Arterial Pulsation

    Nagaoka Ryo, Arakawa Mototaka, Kobayashi Kazuto, Yoshizawa Shin, Umemura Shin-ichiro, Saijo Yoshifumi

    The Computational Mechanics Conference　2014　(27)　362-363　2014/11/22

    Publisher: The Japan Society of Mechanical Engineers

    ISSN：1348-026X

  80. Measurement of propagation wave velocity of thyroid induced by pulsation Peer-reviewed

    Ryo Nagaoka, Shin Yoshizawa, Shin Ichiro Umemura, Yoshifumi Saijo, Kazuto Kobayashi

    IEEE International Ultrasonics Symposium, IUS　1136-1139　2014/10/20

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2014.0279 　

    ISSN：1948-5719

    eISSN：1948-5727

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    Shear wave imaging is a technique with ultrasound that estimates tissue stiffness by measuring shear wave induced by Push Beam, which is generated by acoustic radiation force. However, the technique requires Push Beam for a duration of several hundred micron seconds to deform tissue, and a decay of estimate accuracy may be attributed to out-of-focus Push Beam generated by motions of pulsation and heartbeat. In this presentation, the propagation velocity of thyroid was measured by ultrasound spatial compound imaging with a high temporal resolution. In this proposal method, two components of particle velocity can be obtained by using spatial compound imaging, and two kinds of propagation velocity can be also estimated from the propagation appearance of each component. Verasonic ultrasound scanner (30 MHz, 16 bit, Redmond, WA) and 7.5 MHz UST-5412 Linear Probe (Hitachi Aloka Medical. Ltd.) were used to acquire RF data. Each plane wave was transmitted at 5 different angles, -18, 18, -9, 9, 0, with each time interval of 200μs to acquire echo data for making one spatial compound image. The data of each angle was processed by parallel beamforming, and a spatial compound image was obtained by superposing five B-mode images. Time interval between each spatial compound image is 1 ms. Therefore, the frame rate of the imaging was 1 kfps. A measurement area was thyroid of a 22-year-old healthy male at short axis view. An appearance of the propagation from the artery to thyroid area induced by pulsation was visualized with high-frame-rate ultrasound imaging. There were obvious difference between the shear waves along lateral direction. It's considered that mechanical properties of tissue can be observed from the propagation. According to our past research, the shear wave along muscle fibers was 7.43 ± 0.30 m/s at the frequency of 15 Hz. The muscle fiber direction can be distinguished by the proposal method. These results showed possibility of estimation of tissue stiffness by measuring the shear wave induced by pulsation.

  81. High frame-rate estimation of two-dimensional blood flow vector by bidirectional doppler ultrasound with parallel beamforming Peer-reviewed

    Genta Masuno, Ryo Nagaoka, Osamu Akagawa, Shoya Sasaki, Shin Yoshizawa

    Transactions of Japanese Society for Medical and Biological Engineering　52　331-O-332　2014/08/17

    Publisher: Japan Soc. of Med. Electronics and Biol. Engineering

    DOI： 10.11239/jsmbe.52.O-331 　

    ISSN：1347-443X 1881-4379

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    Ultrasonography has widely used as a simple and useful diagnostic tool in the clinical settings. The blood flow can be estimated with Doppler ultrasound. However, conventional ultrasound system can estimate only one-dimensional component along the ultrasound beam. In this study, the purpose is estimating blood flow vector includes two-dimension by using compounded two different one-dimensional components. Each components was obtained by bidirectional Doppler ultrasound with parallel beam forming using the same linear array probe&lt sup&gt (1)&lt /sup&gt . The frame-rate was increased by using parallel waves. Targets for measurement were carotid artery and a biantennary phantom. This work was implemented with a frame-rate of 100 Hz. We believe this method of estimating the true blood flow leads to early diagnosis of the diseases such as thrombus and plaque in the area of abnormal blood flow.

  82. Focused ultrasound thermal treatment using cavitation-enhanced ultrasonic heating Peer-reviewed

    Shin Yoshizawa, Ryo Takagi, Hiroshi Sasaki, Kota Goto, Nobutaka Abe, Shohei Kodera, Hiroshi Ishii, Takashi Suzuki, Yoshihiro Muragaki, Hiroshi Iseki, Shin-Ichiro Umemura

    Transactions of Japanese Society for Medical and Biological Engineering　52　3-SY-4　2014/08/17

    Publisher: Japan Soc. of Med. Electronics and Biol. Engineering

    DOI： 10.11239/jsmbe.52.SY-3 　

    ISSN：1347-443X 1881-4379

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    High-intensity focused ultrasound (HIFU) causes selective tissue necrosis through heating and is used for a noninvasive treatment of cancer therapy. However, HIFU thermal treatment has a problem of long treatment time because cooling time is needed between two consecutive shots of focused ultrasound exposure to avoid near-field heating owing to heat accumulation. It is known that acoustic cavitation generated in the focal region of HIFU enhances tissue heating. The objective of this study is to develop a method to accelerate HIFU thermal treatment by using cavitation bubbles. Cavitation bubbles were generated at six positions in the direction perpendicular to ultrasound propagation and they were observed by high-speed ultrasound imaging in real time. The coagulation volumes of chicken breast with and without cavitation bubbles were compared. The results show the high efficiency of the proposed HIFU exposure sequence using cavitation-enhanced heating for HIFU thermal treatment.

  83. Visualization of pulse propagation with high frame rate spatial compound imaging Peer-reviewed

    Ryo Nagaoka, Genta Masuno, Kazuto Kobayashi, Shin Yoshizawa, Shin-ichiro Umemura, Yoshifumi Saijo

    Transactions of Japanese Society for Medical and Biological Engineering　52　353-O-354　2014/08/17

    Publisher: Japan Soc. of Med. Electronics and Biol. Engineering

    DOI： 10.11239/jsmbe.52.O-353 　

    ISSN：1347-443X 1881-4379

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    Shear wave Imaging is a technique that estimates tissue stiffness by measuring shear wave induced by Push Beam. However, a decay of estimate accuracy may accrue due to motions of such as pulsation and breathing. In this presentation, we propose estimation method of tissue stiffness based on the pulse propagation.Verasonic and 7.5 MHz Linear Probe were utilized to acquire raw data. The frame rate was 1 kfps. The identical data was used to measure the velocity by a modified 1D-cross-correlation-algorithm. A measurement area was right common carotid artery of 24-year-old healthy male.The pulse propagation was visualized with high-frame-rate ultrasound imaging. The dispersion-relation was observed. For example, the velocity of artery was 6.08 ± 0.19 m/s, and that of muscle was 7.43 ± 0.30 m/s at 15 Hz. It was possible to visualize the appearance of propagation induced by pulsation. The dispersion relation was revealed by the proposal method.

  84. Elimination of HIFU Components in Monitoring of High-Intensity Focused Ultrasound Lesion Formation

    TAKAGI Ryo, MATSUURA Keiko, IWASAKI Ryosuke, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    IEICE technical report. Ultrasonics　114　(102)　9-12　2014/06/23

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    Ultrasonic detection of focal tissue coagulation thermally induced by high-intensity focused ultrasound (HIFU) has been difficult without the involvement of microbubbles. A significant length of interval between HIFU shots is set for monitoring target tissue to avoid interference between HIFU noise and RF echo signals in conventional ultrasound monitoring of HIFU treatment. This way, it is difficult to detect tissue changes in the order of milliseconds, which is required for dynamically controlling the HIFU exposure. In this study, a new filtering method to handle RF signals before beam forming is proposed, which will enable truly real-time detection of tissue coagulation during HIFU exposure.

  85. 超音波医学におけるバブル 基礎から応用まで 超音波生成したキャビテーション気泡の超音波観察

    吉澤 晋, 高木 亮, 佐々木 博史, 佐々木 翔也, 阿部 信隆, 小寺 祥平, 村垣 善浩, 伊関 洋, 梅村 晋一郎

    超音波医学　41　(Suppl.)　S274-S274　2014/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

  86. 高速超音波イメージング下でのキャビテーション援用超音波加熱治療手法の開発

    吉澤 晋, 高木 亮, 佐々木 博史, 後藤 功太, 阿部 信隆, 小寺 祥平, 村垣 善浩, 伊関 洋, 梅村 晋一郎

    超音波医学　41　(Suppl.)　S451-S451　2014/04

    Publisher: (公社)日本超音波医学会

    ISSN：1346-1176

  87. キャビテーションを用いた超音波加熱治療法

    吉澤晋, 中村高太郎, 浅井歩, 佐々木博史, 梅村晋一郎

    超音波テクノ　26　(2)　80-83　2014/04/01

  88. Analysis on Cavitation Region Induced by Positive and Negative Acoustic Pressure

    YASUDA Jun, MIYASHITA Takuya, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    IEICE technical report. Ultrasonics　113　(412)　15-20　2014/01/27

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    Cavitation bubbles have much potential for therapeutic treatments such as high-intensity focused ultrasound (HIFU) treatment. In HIFU treatment method, highly efficient as well as controlled generation of them is important to utilize them effectively as well as safely. However, producing strong negative pressure for generating cavitation bubbles by focused ultrasound is difficult due to the nonlinear propagation. To solve this problem, we have suggested Dual Frequency Ultrasound Exposure method. In this study, cavitation bubbles generated by Dual Frequency Ultrasound Exposure were observed by high-speed camera, and acoustic pressure distribution around focal area was measured by automatic acoustic pressure measurement system. As a result, the measured negative and positive pressure distributions agreed well with the optically observed distributions of cavitation inception and cavitation cloud growth.

  89. 2B34 Highly efficient heating by cavitation bubbles in multiple focal spots in high intensity focused ultrasound treatment

    GOTO Kota, SASAKI Hiroshi, MIYASHITA Takuya, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    2014　(26)　319-320　2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  90. 2B36 Estimation of Coagulation Region by Using Ultrasonic Imaging in Presence of Cavitation Bubbles

    MATSUURA Keiko, TAKAGI Ryo, SASAKI Syoya, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    2014　(26)　323-324　2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  91. 2B21 Quantitative Measurement of High-Intensity Focused Ultrasound Pressure Field by Optical Phase Contrast

    SYAHID Mohd, MIYASAKA Ryo, YASUDA Jun, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    2014　(26)　303-304　2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  92. 2B33 Analysis of Cavitation-enhanced HIFU Heating by Taking Acoustic Emission from Cavitation Bubbles into Account

    Miyashita Takuya, Yasuda Jun, Yoshizawa Shin, Umemura Shin-ichiro

    2014　(26)　317-318　2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  93. Quantitative Measurement of Highly Focused Ultrasound Pressure Field by Optical Shadowgraph Peer-reviewed

    R. Miyasaka, S. Harigane, S. Yoshizawa, S. Umemura

    3RD INTERNATIONAL SYMPOSIUM ON LASER ULTRASONICS AND ADVANCED SENSING　520　(1)　012026　2014

    Publisher: IOP PUBLISHING LTD

    DOI： 10.1088/1742-6596/520/1/012026 　

    ISSN：1742-6588

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    In the development of medical ultrasound techniques, fast and accurate pressure field measurement is important. The most common method to measure an ultrasound pressure field is mechanically scanning a hydrophone, which takes a long time and might disturb the acoustic field. In this study, we used an optical shadowgraph method. To perform this method quantitatively, it is important to define the optical propagation length precisely. For this purpose, a holographic diffuser was used as the imaging screen. Combined with a computed tomography (CT) algorithm, a pressure field was reconstructed, and the result was compared with that of hydrophone measurement. By using two shadowgraph data from short and long propagation lengths, the pressure field was successfully reconstructed even at a pressure level for high intensity focused ultrasound (HIFU) treatment.

  94. 2P5-19 Highly Efficient Cavitation-Enhanced Heating with Dual-Frequency Ultrasound Exposure in High-Intensity Focused Ultrasound Treatment(Poster Session)

    Sasaki Hiroshi, Yasuda Jun, Takagi Ryo, Miyashita Takuya, Goto Kota, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　34　337-338　2013/11/20

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  95. 2P5-7 Quantitative Measurement of Focused Ultrasound Pressure Field by Background-subtracted Shadowgraph Using Holographic Diffuser as Screen(Poster Session)

    Miyasaka Ryo, Yasuda Jun, Syahid Mohd, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　34　313-314　2013/11/20

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  96. 3J5-2 Monitoring of High-Intensity Focused Ultrasound Lesion Formation Using Decorrelation Between High-Speed Ultrasonic Images by Parallel Beamforming(Biomedical Ultrasound 1)

    Sasaki Shoya, Takagi Ryo, Matsuura Keiko, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　34　393-394　2013/11/20

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  97. 2P5-18 Effects of Rose Bengal on Cavitation Generation in Gel Phantom Investigated using High-Speed Camera(Poster Session)

    Yasuda Jun, Miyashita Takuya, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　34　335-336　2013/11/20

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  98. 3P5-19 Two-dimensional Blood Flow Vector obtained by Bidirectional Doppler Ultrasound with Parallel Beamforming(Poster Session)

    Masuno Genta, Nagaoka Ryo, Sasaki Shoya, Yoshizawa Shin, Umemura Shinichiro, Saijo Yoshifumi

    Proceedings of Symposium on Ultrasonic Electronics　34　527-528　2013/11/20

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  99. Adaptive 2-dimension Displacement Estimation on Medical Ultrasonography

    YAMAMOTO Mariko, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    IEICE technical report. Ultrasonics　113　(284)　25-30　2013/11/11

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    We have applied the minimum variance adaptive beamformer to displacement estimation in medical ultrasound imaging and shown improvement in estimation accuracy compared to the conventional method using autocorrelation and Least-square method at low SNR. The proposed method calibrates the weights of trasnducer signals and more improvement was expected along the lateral axis than along the longitudinal axis, while comparable improvements were found by the numerical experiment.

  100. Therapeutic Imaging Using Decorrelation of Ultrasound RF Signal in Cavitation-enhanced Ultrasound Thermal Therapy

    MATSUURA Keiko, TAKAGI Ryo, SASAKI Syoya, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    IEICE technical report. Ultrasonics　113　(284)　31-36　2013/11/04

    Publisher: The Institute of Electronics, Information and Communication Engineers

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    HIFU is a medical technology to coagulate tissue by its acoustic energy. A dependable imaging technology is essential for establishing its accuracy and safety. Minor alternation of ultrasound RF signal in echography due to coagulation is focused in this study. By mapping the decrease in cross-correlation coefficient between frames, we succeeded in estimating the coagulate area in the existence of cavitation bubbles that were generated around the focal spot due to the high ultrasonic intensity.

  101. Analysis of cavitation-enhanced heating and acoustic emission from cavitation in a focused ultrasound field

    Miyashita Takuya, Yasuda Jun, Yoshizawa Shin, Umemura Shin-ichiro

    IEICE technical report. Ultrasonics　113　(201)　19-24　2013/09/12

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    High-intensity focused ultrasound (HIFU) is a noninvasive method for cancer treatments. However, there is a problem that it takes for several hours to treat a large tumor. To shorten the treatment time, there is need for the development of a highly-efficient method. It is known that cavitation bubbles accelerate the HIFU heating treatment. In this study, the enhancement of the heating by cavitation was estimated in a numeral simulation solving a bio-heat transfer equation by increasing the absorption coefficients and heat source in and out of the volume of cavitation bubbles. The absorption coefficient and the amount of the generated heat were calculated by a curve fitting between the temperature rise in experiment and simulation. Finally, we investigated the accuracy of the model by measuring acoustic emission from cavitation in a focused ultrasound field.

  102. 【医療情報誘導治療の最新】 HIFU治療におけるマルチモダリティナビゲーションシステムの開発

    村垣 善浩, 阿部 信隆, 仲本 秀和, 荒井 修, 鈴木 孝司, 岡本 淳, 小寺 祥平, 石井 宏志, 中丸 小百合, 川畑 健一, 吉澤 晋, 梅村 晋一郎, 伊関 洋

    映像情報Medical　45　(7)　597-603　2013/07

    Publisher: 産業開発機構(株)

    ISSN：1346-1354

  103. 2A18 Quantitative Measurement of Highly Focused Ultrasound Pressure Field by Optical Shadowgraph

    MIYASAKA Ryo, HARIGANE Soichiro, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    2013　(25)　267-268　2013/01/08

    Publisher: The Japan Society of Mechanical Engineers

  104. 2A17 Ultrasound Monitoring of Tissue Coagulation Induced by High-Intensity Focused Ultrasound

    SASAKI Shoya, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    2013　(25)　265-266　2013/01/08

    Publisher: The Japan Society of Mechanical Engineers

  105. 2A16 Tissue coagulation enlarged by cavitation babbles in multiple focal spots in high intensity focused ultrasound treatment

    SASAKI Hiroshi, NAKAMURA Kotaro, ASAI Ayumu, YOSIZAWA Shin, UMEMURA Shin-ichiro

    2013　(25)　263-264　2013/01/08

    Publisher: The Japan Society of Mechanical Engineers

  106. 2A15 Analysis on Enhanced Ultrasonic Absorption by Cavitation Bubbles in Ultrasound Thermal Treatment

    OKANO Hiroki, ASAI Ayumu, YASUDA Jun, YOSHIZAWA Shin, UMEMURA Shinichiro

    2013　(25)　261-262　2013/01/08

    Publisher: The Japan Society of Mechanical Engineers

  107. 3I-1 Enhancement of Focal Ultrasonic Treatment by Microbubbles(Invited Talk 3)

    Umemura Shin-ichiro, Kawabata Ken-ichi, Yoshizawa Shin

    Proceedings of Symposium on Ultrasonic Electronics　33　407-408　2012/11/13

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  108. 3Pa5-7 Large Volume Coagulation Utilizing Multiple Cavitation Clouds Generated by 32 Channel Drive Circuits(Poster Session)

    Nakamura Kotaro, Asai Ayumu, Takada Keisuke, Sasaki Hiroshi, Okano Hiroki, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　33　385-386　2012/11/13

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  109. 3Pa5-8 Efficient Generation of Cavitation bubbles in Gel Phantom by Dual-Frequency Ultrasound Exposure(Poster Session)

    Yasuda Jun, Asai Ayumu, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　33　387-388　2012/11/13

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  110. 3Pa5-10 Effect of BSA Concentration on Cavitation Bubbles in Gel Phantom(Poster Session)

    Asai Ayumu, Yasuda Jun, Okano Hiroki, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　33　391-392　2012/11/13

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  111. 1J5-2 Optical Phase Contrast Mapping of Highly Focused Ultrasonic Fields(Biomedical Ultrasound)

    Harigane Soichiro, Miyasaka Ryo, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　33　127-128　2012/11/13

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  112. 実用化を見据えた研究・開発 PDTの発展に向けて 先端医療機器開発における国際標準化の役割

    岸本 眞治, 村垣 善浩, 岡本 淳, 吉光 喜太郎, 鈴木 孝司, 伊関 洋, 吉澤 晋, 梅村 晋一郎, 植松 美幸, 松岡 厚子, 阿部 信隆, 仲本 秀和, 鏑木 正志, 川畑 健一, 石井 宏志

    日本レーザー医学会誌　33　(3)　282-282　2012/10

    Publisher: (NPO)日本レーザー医学会

    ISSN：0288-6200

    eISSN：1881-1639

  113. 新たな低侵襲治療を目指して トリガパルスを用いた高効率集束超音波治療

    村垣 善浩, 和田 章秀, 阿部 信隆, 仲本 秀和, 伊関 洋, 鈴木 孝司, 梅村 晋一郎, 吉澤 晋, 川畑 健一, 石井 宏志, 吉光 喜太郎, 岡本 淳, 小西 良幸

    日本コンピュータ外科学会誌　14　(3)　158-159　2012/10

    Publisher: (一社)日本コンピュータ外科学会

    ISSN：1344-9486

    eISSN：1884-5770

  114. Enhancement of cavitation inception by second-harmonic superimposition Peer-reviewed

    Shin Yoshizawa, Ryo Takagi, Jun Yasuda, Shin ichiro Umemura

    AIP Conference Proceedings　1474　(1)　235-238　2012/05

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.4749339 　

    ISSN：0094-243X

    eISSN：1551-7616

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    High-intensity focused ultrasound (HIFU) treatment with cavitation bubbles has attracted much attention because they enhance the therapeutic efficacy of HIFU. Negative acoustic pressure is known toprimarily determine the cavitation threshold. However, it is hard to generate highly negative acoustic pressure over the cavitation threshold by ultrasonic focusing because of the nonlinear propagation. The sequence, starting with the second-harmonic superimposed pulse waves enhancing the peak negative pressure, and followed by those enhancing the peak positive pressure, demonstrated the highest efficiency in cavitation inception. A high speed camera showed that the negative-pressure enhanced pulse waves produced a small cloud of cavitated microbubbles at the first stage and that the positive-pressure enhanced pulse waves expanded the microbubble cloud at the second stage. © 2012 American Institute of Physics.

  115. Detection of HIFU-induced coagulation by motion-compensated decorrelation of RF echo signals Peer-reviewed

    Shin Ichiro Umemura, Ryo Matsuzawa, Takashi Shishitani, Shin Yoshizawa

    IEEE International Ultrasonics Symposium, IUS　2611-2614　2012

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2012.0654 　

    ISSN：1948-5719

    eISSN：1948-5727

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    Correlation between the ultrasonic echoes has been used to detect the changes of the tissue during high-intensity focused ultrasound (HIFU) exposure, but it tends be lost when tissue coagulation has progressed. In this study, the loss of correlation itself is utilized to detect the tissue coagulation while compensating the local tissue motion. In the experiment with freshly excised and degassed porcine liver, localized decrease in correlation was observed at and around the HIFU focus. The area of decorrelation between each adjacent two frames, separated about 1 s, agreed well with the actual lesion. © 2012 IEEE.

  116. Efficient generation of cavitation cloud by dual-frequency ultrasound exposure in optically transparent gel Peer-reviewed

    Jun Yasuda, Ayumu Asai, Shin Yoshizawa, Shin Ichiro Umemura

    IEEE International Ultrasonics Symposium, IUS　2607-2610　2012

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2012.0653 　

    ISSN：1948-5719

    eISSN：1948-5727

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    Cavitation bubbles are known to enhance HIFU treatment. To generate them at a high efficiency, ultrasound waveforms emphasizing either positive or negative pressure were synthesized by superimposing the second harmonic onto the fundamental and combined in an exposure sequence. In this study, four different types of sequences were compared. Negative-pressure emphasized waves immediately followed by positive-pressure emphasized waves resulted in the highest efficiency. The pressure-release surfaces provided by the cavitation bubbles generated by the former waves may have converted the latter waves to highly negative-pressure emphasized waves. © 2012 IEEE.

  117. Optimization of phase shift of the transducer for high intensity focused ultrasound (HIFU) Peer-reviewed

    Mariko Yamamoto, Shin Yoshizawa, Shin Ichiro Umemura

    IEEE International Ultrasonics Symposium, IUS　1625-1628　2012

    Publisher: IEEE

    DOI： 10.1109/ULTSYM.2012.0407 　

    ISSN：1948-5719

    eISSN：1948-5727

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    A method of beam design for a high-intensity focused ultrasound (HIFU) array transducer, a technology that has recently made significant progress, can be an essential tool to utilize the potential of an HIFU. A method of beam design that constrains the apodization weights of each element based on the least squares method was proposed to meet clinical needs in HIFU therapy in terms of the total power at the focal spot and the suppression of the near-field power density. The difficulty in calculation was solved with orthonormalized maps introduced using a fixed-point theorem. The proposed method was applied to the beamforming design to form a uniform wide beam and a Bessel beam with uniform phase shift as the optimized beam shapes. There was an improvement of approximately 20% in homogeneity and 70% in power efficiency. The proposed method has proven useful in forming a uniform wide beam, and the success of our method suggests its potential usefulness. © 2012 IEEE.

  118. Ultrasound image based visual tracking of kidney by utilizing multi-templates

    FUNAMOTO T., KOIZUMI N., SEO J., NOMIYA A., YOSHIZAWA S., YOSHINAKA K., SUGITA N., MATSUMOTO Y., HOMMA Y., MITSUISHI M.

    13　(3)　190-191　2011/11/22

    ISSN：1344-9486

  119. 3J5-2 Thermal simulation of cavitation enhanced ultrasonic heating verified with tissue mimicking gel(Medical Ultrasound)

    Moriyama Tatsuya, Asai Ayumu, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　32　581-582　2011/11/08

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  120. 3Pb5-6 Simulated B-mode image from acoustic impedance map of HIFU-exposed specimen(Poster Session)

    Shishitani Takashi, Matsuzawa Ryo, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　32　541-542　2011/11/08

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  121. 3Pb5-1 Therapeutic array transducer element using coresonance between hemispherical piezoceramic shell and water sphere(Poster Session)

    Otsu Kenji, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　32　531-532　2011/11/08

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  122. 3Pb5-5 Ultrasonic Monitoring of High Intensity Focused Ultrasound Lesions Using Sub-Image Correlation(Poster Session)

    Matsuzawa Ryo, Shishitani Takashi, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　32　539-540　2011/11/08

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  123. 3Pb5-7 Analysis of temperature increase in excised porcine liver tissue induced by cavitation-enhanced HIFU(Poster Session)

    Iwasaki Eiko, Asai Ayumu, Moriyama Tatsuya, Shishitani Takashi, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　32　543-544　2011/11/08

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  124. 3Pb5-8 Efficient Generation of Cavitation Cloud by Dual-Frequency Ultrasound Exposure(Poster Session)

    Yasuda Jun, Takagi Ryo, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　32　545-546　2011/11/08

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  125. 3Pb5-4 3D-Quantitative Optical Measurement of Asymmetrically Focused Ultrasound Pressure Field(Poster Session)

    Shimazaki Yuta, Harigane Soichiro, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　32　537-538　2011/11/08

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  126. キャビテーション気泡による加熱増強効果を利用した超音波治療

    吉澤晋

    超音波テクノ　23　(5)　91-95　2011/10

  127. マイクロバブルの応用

    S. Yoshizawa, Yoichiro Matsumoto

    Journal of Clinical and Experimental Medicine　238　(2)　157-162　2011/07/09

    Publisher: 医歯薬出版

    ISSN：0039-2359

  128. マイクロ気泡による集束超音波治療の効率化

    梅村 晋一郎, 吉澤 晋, 稲葉 脩太

    ナノ医工学年報　5　(1)　111-120　2011

    Publisher: 東北大学グローバルCOEプログラム「新世紀世界の成長焦点に築くナノ医工学拠点」

    ISSN：1882-4692

  129. 新評価科学の構築:疾患伴侶動物を対象とした新規治療機器の評価手法開発

    村垣善浩, 村垣善浩, 伊関洋, 伊関洋, 鈴木孝司, 吉光喜太郎, 石井宏志, 和田章秀, 岡本芳晴, 仲本秀和, 阿部信隆, 川畑健一, 梅村晋一郎, 吉澤晋

    日本生体医工学会大会プログラム・論文集(CD−ROM)　50th　ROMBUNNO.OS1-2-3　2011

  130. Effects of Lamb waves in a single-element High Intensity Focused Ultrasound transducer Peer-reviewed

    Kenji Otsu, Yasuhiro Kaneshima, Shin Yoshizawa, Shin Ichiro Umemura

    AIP Conference Proceedings　1359　211-214　2011

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.3607907 　

    ISSN：0094-243X

    eISSN：1551-7616

    More details Close

    In a spherical single-element piezoceramic transducer for HIFU (High Intensity Focused Ultrasound) treatment, the modes of plate wave propagation within the ceramic were observed in addition to the pure thickness-mode vibration in experiment. These may potentially influence the therapeutic effects. In this study, we analyzed the vibrational behavior of an air-backed single-element spherical PZT transducer in two ways: by reconstruction of the sound source distribution from the measured ultrasound pressure field, and by numerical simulation of vibration based on a Finite Element Method (FEM). In the two-dimensional Fourier analysis performed in the time and space domains, the radial wavenumber spectrum at the driving frequency showed a high peak, second to the highest peak corresponding to the uniform vibration. This corresponds to waves propagating as leaky Lamb waves from the circumferential edge towards the center of the spherical transducer. These waves propagate at a constant angle with the shell surface in water, and form the relatively large lobes on the acoustic axis on the nearside of the geometric focus. The acoustic energy of the nearside lobes may cause additional near-field heating of tissues which should not to be treated. © 2011 American Institute of Physics.

  131. Gel phantom containing controlled air to test Triggered HIFU exposure sequence Peer-reviewed

    Kengo Takimoto, Tatsuya Moriyama, Ryo Takagi, Shin Yoshizawa, Shin Ichiro Umemura

    AIP Conference Proceedings　1359　109-113　2011

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.3607891 　

    ISSN：0094-243X

    eISSN：1551-7616

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    An optically transparent phantom containing a controlled content of air was developed for dosimetry studies of Triggered HIFU (High Intensity Focused Ultrasound) exposure, in which a high intensity short pulse (Triggering Pulse) is used in order to trigger cavitation and enhance the heating effect of an immediately subsequent continuous wave (CW) exposure CW (Heating Waves) with intensity and duration typical of conventional HIFU treatment. The air content was controlled by the time and pressure of degassing during gel formation. We measured the temperature change in the gel with a film thermocouple at the HIFU focus. The temperature rise induced by a 100 μs Triggering Pulse at 10 kW/cm of followed by a 10 s CW exposure at 0.2 kW/cm was higher than the Heating Waves alone, by up to six to ten times. © 2011 American Institute of Physics. 2 2

  132. Minimally invasive intracardiac intervention using high intensity focused ultrasound Peer-reviewed

    Takashi Mochizuki, Taizou Kihar, Kazunori Itani, Kouji Ogawa, Shin Yoshizawa, Shin Ichiro Umemura, Gontaro Kitazumi, Yasumasa Katsuike, Toshio Chiba

    AIP Conference Proceedings　1359　241-245　2011

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.3607912 　

    ISSN：0094-243X

    eISSN：1551-7616

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    This paper describes the development of a HIFU irradiation system with the goal of devising an intrauterine means of preventing hypoplastic left heart syndrome (HLHS) or balloon atrial septostomy (BAS). Four large confocal ultrasound transducers were adopted in a large animal experiment to simulate an intervention for the treatment of fetuses in utero. © 2011 American Institute of Physics.

  133. 2P-48 Frequency-Dependent Phase Change threshold of Perfluorocarbon Nanodroplets(Poster Session)

    Takimoto Kengo, Moriyama Tatsuya, Yoshizawa Shin, Asami Rei, Kawabata Ken-ichi, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　31　385-386　2010/12/06

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  134. 2P-54 Creation of Multiple Cavitation Clouds by Phased Array Transducer Driven with Staircase Voltage(Poster Session)

    Okada Jumpei, Inaba Yuta, Moriyama Tatsuya, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　31　397-398　2010/12/06

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  135. 2P-44 Cavitation Inception by Dual-Frequency Excitation in High Intensity Focused Ultrasound Treatment(Poster Session)

    Takagi Ryo, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　31　377-378　2010/12/06

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  136. 2P-46 Study on Change in Sound Speed by HIFU-Exposure in Chicken Breast Muscle(Poster Session)

    Shishitani Takashi, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　31　381-382　2010/12/06

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  137. 2P-52 High Speed Observation of Multiple Cavitation Cloud Behavior Induced by HIFU(Poster Session)

    Inaba Yuta, Moriyama Tatsuya, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　31　393-394　2010/12/06

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  138. 1Pb-60 Analysis of Non-uniform Vibration of Focused Ultrasound Transducer Using Time-Reversal Method(Poster Session)

    Komura Yuji, Otsu Kenji, Yoshizawa Shin, Umemura Shin-iciro

    Proceedings of Symposium on Ultrasonic Electronics　31　261-262　2010/12/06

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  139. 1Pb-15 On the Optical Measurement of Focused Ultrasound Pressure Field(Poster Session)

    Omura Ryosuke, Shimazaki Yuta, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　31　171-172　2010/12/06

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  140. 1Pb-53 Breathing Mode Ceramic Element for Therapeutic Array Transducer(Poster Session)

    Otsu Kenji, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　31　247-248　2010/12/06

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  141. 1Pb-63 Effect of thin intervening layer on acoustic impedance measurement of soft tissue using ultrasonic microscope(Poster Session)

    Satoh Yusuke, Shishitani Takashi, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　31　267-268　2010/12/06

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  142. Staircase Voltage MOSFET Driver Circuit for High Intensity Forcused Ultrasound

    TAKADA Keisuke, OKADA Jumpei, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    IEICE technical report　110　(213)　117-120　2010/09/22

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    In ultrasound treatment, an array transducer with a number of elements becomes to be used. Then, we need a class D amplifier which is inexpensive, compact, and low power loss. In square wave drive, odd harmonics are large, so that we designed a class D amplifier which can eliminate the third and fifth harmonics by staircase voltage drive and tested the performance of this amplifier

  143. 3D reconstruction of HIFU(high intensity focused ultrasound) pressure field from optical mearuement

    SHIMAZAKI Yuta, OMURA Ryosuke, YOSHIZAWA Shin, UMEMURA Shin-itiro

    IEICE technical report　110　(213)　13-16　2010/09/22

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

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    To ensure the safety and accuracy of medical, typically therapeutic, ultrasound an accurate measurement of the ultrasonic field is especially important. The optical ultrasonic field mapping such as a schlieren method has advantages over the measurement with a hydrophone in its orders-of-magnitude faster speed and its non-interference nature to the acoustic field. However, the ultrasonic field obtained by a conventional schlieren method is rather qualitative. By modifying the optical configuration and signal processing, we obtained a pressure field map preserving the sign of the ultrasonic pressure, which is necessary for 3-D reconstruction of the ultrasonic field using a CT algorithm.

  144. Vibration Analysis of Single-element High Intensity Focused Ultrasound Transducer : Effects of Leaky Lamb Waves

    OTSU Kenji, KANESHIMA Yasuhiro, KOMURA Yuji, YOSHIZAWA Shin, UMEMURA Shin-ichiro

    IEICE technical report　110　(213)　111-116　2010/09/22

    Publisher: The Institute of Electronics, Information and Communication Engineers

    ISSN：0913-5685

    More details Close

    In a spherical single-element piezoceramic transducer for HIFU (High Intensity Focused Ultrasound) treatment, the unwanted modes of plate wave propagation within the ceramic were observed in addition to the pure thickness-mode vibration in experiment. In this study, we analyzed the vibration behavior of a single-element spherical PZT transducer in two ways: by reconstruction of the sound source distribution from the measured ultrasound pressure field and by numerical simulation of vibration based on a Finite Element Method (FEM). In the two-dimensional Fourier analysis, the radial wavenumber spectrum showed a secondary peak, corresponding to waves propagating along the spherical transducer like leaky Lamb waves. The leaked waves propagate in water and form the relatively large lobes on the propagating axis in the nearside of the geometric focus. The acoustic energy of the nearside lobes may cause additional near-field heating of the tissues, which should not be treated.

  145. 2P1-G24 Construction Methodology for Non-Invasive Ultrasound Theragnostic System : 2^<nd> report

    KOIZUMI Norihiro, SEO Joonho, DEUKHEE Lee, NOMIYA Akira, YOSHINAKA Kiyoshi, YOSHIZAWA Shin, SUGITA Naohiko, HOMMA Yukio, MATSUMOTO Yoichiro, MITSUISHI Mamoru

    2010　"2P1-G24(1)"-"2P1-G24(4)"　2010

    Publisher: The Japan Society of Mechanical Engineers

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    We propose a non-invasive ultrasound theragnostic system that tracks movement in an affected area (kidney stones, in this study) by irradiating it with high-intensity focused ultrasound (HIFU). In this paper, the concept behind a novel medical support system that integrates therapy and diagnostics (theragnostics), is illustrated. The required functions for the proposed system are discussed and an overview of the constructed system configuration is illustrated. Problems of stone motion tracking by ultrasonography are described. To overcome with this problem, we should take 2 approaches. The first approach is to minimize the servoing error to enhance both the efficiency of the therapy and the safety of the patient. The second approach is to reduce the effect of the servoing error. Concerning the first approach, we propose 2 solutions. One is robust detection of the stone position by shape information. Another is the controller that compensates for periodic motion of the affected area. Concerning the second approach, we propse a solution to control HIFU irradiation power in accordance with the servoing error, mainly to enhance the safety of the patient.

  146. マイクロ気泡による集束超音波治療の加速 : 相変化ナノ液滴やキャビテーションの応用

    梅村 晋一郎, 吉澤 晋

    ナノ医工学年報　4　(1)　109-118　2010

    Publisher: 東北大学グローバルCOEプログラム「新世紀世界の成長焦点に築くナノ医工学拠点」

    ISSN：1882-4692

  147. Effects of lamb wave in therapeutic ultrasound transducer by vibration analysis Peer-reviewed

    Kenji Otsu, Yasuhiro Kaneshima, Shin Yoshizawa, Shin Ichiro Umemura

    IFMBE Proceedings　31 IFMBE　1640-1643　2010

    Publisher: SPRINGER

    DOI： 10.1007/978-3-642-14515-5_417 　

    ISSN：1680-0737

    More details Close

    A typical single-element High Intensity Focused Ultrasound (HIFU) transducer has a spherical shell in order to focus the acoustic energy onto the focal spot. In a prototype PZT transducer we constructed, a mode of plate wave propagation in the shell was experimentally observed in addition to the uniform thickness vibration mode. Such an unwanted wave component may deform the ultrasonic power deposition pattern, which can potentially influence the therapeutic effects. In this study, we analyzed the vibrating behavior of a spherical piezoelectric transducer in two ways: by the reconstruction of the sound source distribution from a measured pressure field and by a numerical simulation of vibration based on a Finite Element Method (FEM). In the two-dimensional Fourier analysis performed in both time and space domain, the radial wavenumber spectrum showed a high peak, second to the highest peak corresponding to the uniform vibration. This corresponds to the waves propagating from the circumference towards the center of the spherical transducer like a symmetric mode of leaky Lamb waves. The leaked waves propagate at a constant angle with the shell surface in water and form a relatively large lobe on the axis at the nearside of the geometric focus. This nearside lobe, also observed in the measurement, may cause additional near field heating of tissues. © 2010 International Federation for Medical and Biological Engineering.

  148. Acoustic impedance evaluation of thermally denatured and non-denatured biological tissues Peer-reviewed

    T. Shishitani, S. Yoshizawa, S. Umemura

    IFMBE Proceedings　31 IFMBE　1629-1632　2010

    Publisher: SPRINGER

    DOI： 10.1007/978-3-642-14515-5_414 　

    ISSN：1680-0737

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    High-intensity focused ultrasound (HIFU) is a method to treat non-superficial tumors by inducing high temperature to coagulate them. In this study, we measured the acoustic impedance distribution and sound speed of thermally-denatured and nondenatured chicken breast muscles. The thermally-denatured specimen was obtained by exposure to HIFU at about 800 W/cm for 60 s. The condition was so chosen that cavitations would not occur. © 2010 International Federation for Medical and Biological Engineering. 2

  149. 3J5-2 Vibration Analysis of High Intensity Focused Ultrasound Source using Time Reversal : Effects of Lamb Waves(Medical Acoustics)

    Kaneshima Yasuhiro, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　30　403-404　2009/11/18

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

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    In HIFU (High Intensity Focused Ultrasound) therapy, ultrasound is focused on target tissue for coagulation. This method is attracting attention as noninvasive therapeutic modality, and being researched widely from basic study to clinical application. Accurate measurement of the ultrasound pressure field is very important in the research areas of HIFU such as biological effects and ultrasound devices. In this study, we reconstructed the distribution of sound source vibration using Time Reversal and investigated the effects of Lamb waves. In the two-dimensional Fourier transform of the sound source vibration in both time and space domain, we found a peak with a finite phase velocity, which may corresponds to Lamb waves propagating from the edge toward the center of the circular transducer.

  150. 2P5-7 Staircase Voltage MOSFET Driver Circuit for Therapeutic Ultrasound(Poster Session)

    Moro Kosuke, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　30　333-334　2009/11/18

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  151. 2P5-8 Vibration Analysis of Therapeutic Ultrasound Transducer by FEM(Poster Session)

    Otsu Kenji, Yoshizawa Shin, Azuma Takashi, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　30　335-336　2009/11/18

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  152. 3P5-20 Acoustic Impedance Evaluation of Thermally-induced Lesion in Biological Tissue using Ultrasonic Microscopy(Poster Session)

    Shishitani Takashi, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　30　561-562　2009/11/18

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  153. 3P5-17 Enhancement of Localized Heating by Ultrasonically Induced Cavitation in High Intensity Focused Ultrasound Treatment(Poster Session)

    Takagi Ryo, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　30　555-556　2009/11/18

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  154. 3P5-18 Coagulation of Large Region by Creating Multiple Cavitation Clouds for HIFU Treatment(Poster Session)

    Inaba Yuta, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　30　557-558　2009/11/18

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  155. 1P2-16 Analysis of Therapeutic Ultrasound Pressure Field with Schlieren Optical System(Poster Session)

    Omura Ryosuke, Yoshizawa Shin, Umemura Shin-ichiro

    Proceedings of Symposium on Ultrasonic Electronics　30　47-48　2009/11/18

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN：1348-8236

  156. 医工連携の実践 治療機器開発のための疾患伴侶動物の試験研究 動物実験とヒト治験の橋渡し

    村垣 善浩, 伊関 洋, 鈴木 孝司, 吉光 喜太郎, 石井 宏志, 和田 章秀, 岡本 芳晴, 佐々木 明, 仲本 秀和, 阿部 信孝, 荒井 修, 川畑 健一, 梅村 晋一郎, 吉澤 晋

    日本コンピュータ外科学会誌　11　(3)　153-154　2009/11

    Publisher: (一社)日本コンピュータ外科学会

    ISSN：1344-9486

    eISSN：1884-5770

  157. Servoing Performance and safety enhancement for the Non-Invasive Ultrasound Theragnostic System

    小泉憲裕, SEO Joonho, 鈴木悠悟, 野宮明, 吉澤晋, 葭仲潔, 杉田直彦, 本間之夫, 松本洋一郎, 光石衛

    日本ロボット学会学術講演会予稿集(CD-ROM)　27th　2009

  158. ナノまたはマイクロ粒子による集束超音波治療効果の強調

    梅村 晋一郎, 吉澤 晋

    ナノ医工学年報　3　(1)　113-122　2009

    Publisher: 東北大学グローバルCOEプログラム「新世紀世界の成長焦点に築くナノ医工学拠点」

    ISSN：1882-4692

  159. 超音波キャビテーションとその治療応用

    吉澤晋, 梅村晋一郎, 松本洋一郎

    マテリアルインテグレーション　22　(6)　48-53　2009

    Publisher: ティー・アイ・シィー

    ISSN：1344-7858

  160. Development of HIFU treatment in which the heating location is controlled using microbubbles Peer-reviewed

    Kenichi Kajiyama, Naoyuki Iida, Keisuke Hasegawa, Shin Yoshizawa, Kiyoshi Yoshinaka, Shu Takagi, Yoichiro Matsumoto

    AIP Conference Proceedings　1113　48-52　2009

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.3131469 　

    ISSN：0094-243X

    eISSN：1551-7616

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    High-intensity focused ultrasound (HIFU) treatment that employs microbubbles to provide enhanced heating has been investigated in order to develop a less invasive and more rapid tumor therapy. Previous studies by us have demonstrated that ultrasound propagation is disturbed when there are microbubbles in front of the focus. In this study, we develop a method for obtaining enhanced heating by using microbubbles just at the focus, thus avoiding heating on the transducer side. In this method, microbubbles are destroyed in front of the HIFU focus (on the transducer side) by irradiating a very short burst wave of microsecond order, before irradiating the ultrasound waves for heating the focus. The experiment is conducted in a medium of a gel containing microbubbles, and a temperature-sensing liquid crystal sheet is set in the focus to observe the temperature distribution. The ultrasound frequency was 2.2 MHz and the intensity was 5000 W/cm , and 20 burst wave waves were irradiated at pulse repetition frequency of 1 kHz. The number of wave pulses was varied. The continuous-wave frequency, intensity and irradiation time are 2.2 MHz, 1000 W/cm and 60 sec, espectively. As the number of pulses increased, the heating region moves from the transducer side to the focus. This is because microbubbles in front of the focus are destroyed and the ultrasound propagates around the target position effectively. These results suggest that the microbubble distribution and the heating position in the developed HIFU system can be controlled. © 2009 American Institute of Physics. 2 2

  161. 1A1-C11 Construction Methodology for Non-Invasive Ultrasound Theragnostic System

    KOIZUMI Norihiro, LEE Deukhee, OTA Kohei, OTA Ryuhei, YOSHIZAWA Shin, YOSHINAKA Kiyoshi, MATSUMOTO Yoichiro, MITSUISHI Mamoru

    2008　"1A1-C11(1)"-"1A1-C11(4)"　2008/06/06

    Publisher: The Japan Society of Mechanical Engineers

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    The authors have developed a non-invasive ultrasound theragnostic system to decrease the strain of patients and medical doctors. The system we propose tracks and follows movement in an affected area -kidney stones here- while High-Intensity Focused Ultrasound (HIFU) is irradiated onto the area. In this paper, a framework of the non-invasive ultrasound theragnostic system is proposed and illustrated. Specifically, the concept of the system is proposed at first. Secondly, decomposing and reconstructing (structuring) of the functional requirements are discussed. Third, the constructed system, which is based on those structured functional requirements, is illustrated. Fourth, the result of the servoing experiments of the model stone is reported to confirm the effectiveness of the proposed construction methodology and constructed system.

  162. Nonlinear phenomena of acoustic cloud cavitation Peer-reviewed

    Yoichiro Matsumoto, Shin Yoshizawa, Shu Takagi

    AIP Conference Proceedings　1022　237-240　2008

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.2956196 　

    ISSN：0094-243X

    eISSN：1551-7616

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    Acoustic cavitation, which is normally consisted of bubble cluster, has an important role in various fields such as medical, environmental, industrial applications. The strong pressure appears in the case of bubble cluster like a cloud cavitation. As the dynamics of bubbles are strongly influenced by the thermal phenomena inside the bubbles, these phenomena are considered to numerically investigate the behavior the bubble cloud. The pressure wave focuses to the center of the cloud and the pressure inside bubbles extremely increases when the frequency of the pressure wave is near the first mode natural frequency of the cloud. Due to the strong nonlinearity of the pressure wave propagation in the bubbly liquid, a sinusoidal wave changes to the steep waveform in the cloud and it generates high pressure fluctuation near the center of the cloud even when the frequency is much lower than the first mode frequency. © 2008 American Institute of Physics.

  163. Framework of the non-invasive ultrasound theragnostic system Peer-reviewed

    Norihiro Koizumi, Deukhee Lee, Kohei Ota, Shin Yoshizawa, Kiyoshi Yoshinaka, Yoichiro Matsumoto, Mamoru Mitsuishi

    MEDICAL IMAGING AND AUGMENTED REALITY, PROCEEDINGS　5128　231-240　2008

    Publisher: SPRINGER-VERLAG BERLIN

    DOI： 10.1007/978-3-540-79982-5_26 　

    ISSN：0302-9743

    eISSN：1611-3349

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    The authors have developed an Non-Invasive Ultrasound Theragnostic System to decrease the strain of patients and medical doctors. The system we propose tracks and follows movement in an affected area -kidney stones here-while Hi-h-Intensity Focused Ultrasound (HIFU) is irradiated onto the area. In this paper, a framework of the non-invasive ultrasound theragnostic system is proposed and illustrated. Specifically, the concept of the system is proposed at first. Secondly, decomposing and reconstructing (structuring) of the functional requirements are discussed. Third, the constructed system, which is based on those structured functional requirements, is illustrated. Fourth, the result of the servoing experiments of the model stone is reported to confirm the effectiveness of the proposed construction methodology and constructed system.

  164. High Intensity Focused Ultrasound Therapy with Microbubbles

    S. Yoshizawa, S. Umemura, Y. Matsumoto

    11th International Symposium on Advanced Biomedical Ultrasound　2008

  165. 1P1-H06 Feedforward control utilizing real-time information of the integrated system for non invasive ultrasound diagnosis and treatment

    KOIZUMI Norihiro, OTA Kohei, LEE Deukhee, YOSHIZAWA Shin, ITOH Akira, MATSUMOTO Yoichiro, MITSUISHI Mamoru

    2007　"1P1-H06(1)"-"1P1-H06(2)"　2007/05/11

    Publisher: The Japan Society of Mechanical Engineers

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    The authors have developed an integrated system for the non-invasive ultrasound diagnosis and treatment to decrease the load of patients and medical doctors. In this paper, motion of a kidney and abdominal circumference information, which is acquired by a force sensor, are analyzsed at first. Secondly, the authors propose a feedforward controller to enhance the servoing performance of the system for model kidney stones by utilizing real-time information of abdominal circumference. Finally, experimental results show that the constructed system ia appropriate to presume the phase information of stone motion to generate the feedforward term of the controller.

  166. 1P1-H05 Kidney Stone Tracking Framework Using Ultrasonic Radio Frequency Echo Signal

    LEE Deukhee, KOIZUMI Norihiro, OTA Kohei, YOSHIZAWA Shin, ITOH Akira, MATSUMOTO Yoichiro, MITSUISHI Mamoru

    2007　"1P1-H05(1)"-"1P1-H05(3)"　2007/05/11

    Publisher: The Japan Society of Mechanical Engineers

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    The authors are developing an ultrasound-based integrated system for non-invasive diagnosis and treatment of kidney stones. The major goals of the system are to aid to detect kidney stones with ultrasound images and to eliminate them by cloud-cavitaion controlled lithotripsy using high intensity focused ultrasound (HIFU). The target kidney stone of lithotripsy moves during the treatment by breathing. Therefore, real-time motion tracking and servoing of the target kidney stone are necessary in order to improve the accuracy of the treatment and reduce treatment time. This paper describes the feasibility study of real-time 3D tracking and servoing with two ultrasound diagnostic probes and a 3D stage machine using ultrasonic radio frequency (RF) echo signal with regard to the therapeutic goal of the integrated system.

  167. Optimization of Ultrasound Lithotripsy by Ultrasound Monitoring

    OHTA Ryuhei, ITO Akira, YOSHIZAWA Shin, TAKAGI Shu, MATSUMOTO Yoichiro

    34　S306　2007/04/15

    ISSN：1346-1176

  168. 非侵襲超音波診断・治療統合システムにおけるフィード・フォワード制御

    小泉憲裕, 太田耕平, LEE Deukhee, 吉澤晋, 伊藤陽, 松本洋一郎, 光石衛

    精密工学会大会学術講演会講演論文集　2007　2007

  169. 非侵襲超音波診断・治療統合システムのためのリアルタイム呼吸情報取得

    太田耕平, 小泉憲裕, LEE Deukhee, 吉澤晋, 伊藤陽, 松本洋一郎, 光石衛

    精密工学会大会学術講演会講演論文集　2007　2007

  170. 10項 超音波エレクトロニクス研究会(3節 工学研究会,第5章 国際会議・シンポジウム等)

    梅村 晋一郎, 吉澤 晋

    東北大学電気通信研究所研究活動報告　14　300-301　2007/01/01

  171. Behavior of microbubbles in an ultrasound field and medical applications using microbubbles

    S. Yoshizawa, Y. Matsumoto

    Valve technical report　22　(1)　62-66　2007

  172. Real-time imaging of the process of stone crushing by ultrasound Peer-reviewed

    Akira Ito, Shin Yoshizawa, Yukio Kaneko, Haruki Kume, Tadaichi Kitamura, Yoichiro Matsumoto

    AIP Conference Proceedings　911　342-348　2007

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.2744295 　

    ISSN：0094-243X

    eISSN：1551-7616

    More details Close

    A new method of lithotripsy combining high and low frequency ultrasound has been investigated. This method controls generation of cavitation only on the stone surface and utilizes collapse pressure of the bubbles. In order to apply this method for clinical practice, it is important to monitor the process of stone crushing and behavior of cavitation from outside the body. In this study, ultrasound imaging was coupled with a therapeutic ultrasound system for real-time monitoring and targeting of stones. Stone crushing tests have been conducted in vitro and in vivo experiments. In vitro experiment, crushing process of a model stone in a polyacrylamide gel was observed with both ultrasound imaging and a digital video camera. It was observed with ultrasound imaging that the stone was crushed with ultrasound. In vivo experiment, a stone crushing experiment has been conducted in a pig bladder. And a mark of crushing was found on the surface of the stone taken out from the bladder after the irradiation, as well as in vitro experiment. The process of stone crushing in a pig bladder could be monitored with bi-plane ultrasound imaging from outside the body. © 2007 American Institute of Physics.

  173. Numerical Study on Rectified Diffusion of an Oscillating Microbubble in an Ultrasound Field Peer-reviewed

    S. Yoshizawa, Y. Matsumoto

    Proc. of The 1st International Colloquium on Dynamics, Physics and Chemistry of Bubble and Gas-Liquid Boundaries　2007

  174. Development of an integrated system for non-invasive ultrasound diagnosis and treatment

    OTA K., KOIZUMI N., LEE D., YOSHIZAWA S., ITO A., MATSUMOTO Y., MITSUISHI M.

    8　(3)　386-387　2006/12/30

    ISSN：1344-9486

  175. AM06-KN-004 Medical Applications in Fluid Mechanics : Noninvasive Therapeutic Ultrasound with Microbubbles

    Matsumoto,Yoichiro, Fujiwara,Akiko, Yoshizawa,Shin, Kaneko,Yukio

    Proceedings, ... meeting of Japan Society of Fluid Mechanics　2006　(0)　17-20　2006/09

    Publisher: Japan Society of Fluid Mechanics

    ISSN：1342-8004

    More details Close

    Ultrasonic medical applications such as ultrasound diagnosis and High Intensity Focused Ultrasound (HIFU) therapy have recently been the subject of much interest. In these applications, micro-bubbles facilitate the medical treatment by improving the image quality or enhancing the therapeutic effects through localized heating or acoustic emission. In order to treat a diseased part properly and safely, real-time diagnosis with therapy is necessary. The objective of this study is the establishment of the integrative system of real-time ultrasound imaging and minimally invasive HIFU therapy.

  176. Ultrasound Imaging for the Diagnostic and Therapeutic System

    YOSHIZAWA Shin, KANEKO Yukio, FUJIWARA Akiko, MATSUMOTO Yoichiro

    Journal of the Visualization Society of Japan　26　(1)　5-8　2006/07/01

    Publisher: 可視化情報学会

    ISSN：0916-4731

  177. Characterization of the HIFU-induced cloud cavitation for the optimization of high pressure concentration for lithotripsy Peer-reviewed

    Teiichiro Ikeda, Shin Yoshizawa, Yukio Kaneko, Yoichiro Matsumoto

    AIP Conference Proceedings　829　328-332　2006/05/08

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.2205491 　

    ISSN：0094-243X

    eISSN：1551-7616

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    The bubble cloud is a highly scattering object; to the contrary, it is also a strong pressure wave enhancer, if the wavelength and amplitude of the wave is appropriate ones. We've been investigated the stone erosion enhancement in the existence of bubble cloud on the stone surface by using high frequency waveform that immediately followed by low frequency trailing pulse (C-C waveform; Cavitation Control waveform). For the optimization of the high pressure concentration it is needed to know, "how the enhancement of the pressure wave through the bubble cloud" and "how we can estimate the efficiency thorough the passive detection of the reflected signal from the bubble cloud". We measured the "Transmittance" and " Reflection" by two types of acoustic emission sensors, PCD (Passive Cavitation Detector) and DCD (Direct Collapse Detector). The results well depict the characteristics of the HIFU-induced bubble cloud responses. The response curves reveal that the local maxima of the "Transmittance" and "Reflection" occur at the different bubble cloud volume. The PCD signal is higher in the larger bubble cloud band. The DCD signal is larger in the smaller bubble cloud band. These tendencies imply the therapeutic effect through the bubble cloud is optimized in the small bubble cloud region and too much bubbles scatter the incoming ultrasound wave and the ultrasound wave does not efficiently propagates inward the bubble cloud. Thus, for the optimization of the bubble cloud collapse, the cavitation threshold can be the lower limit and the large scattering amplitude from bubble cloud can be the upper limit of the ultrasound conditions. © 2006 American Institute of Physics.

  178. 21101 Real-time Ultrasound Imaging of Process of Ablation Induced by HIFU

    ITO Akira, KANEKO Yukio, YOSHIZAWA Shin, TAKAGI Shu, MATSUMOTO Yoichiro

    2006　(12)　89-90　2006/03/09

    Publisher: The Japan Society of Mechanical Engineers

    More details Close

    It is necessary to accurately understand the condition of the treated region from outside of the body in real-time in HIFU (High Intensity Focused Ultrasound) therapy. In this study, to monitor the condition of the treated region with ultrasound diagnostic system, the ultrasound diagnostic images were compared with the movie taken by a digital video camera during and after ultrasound irradiation. In the ultrasound diagnostic images, high-bright region got shrunk after the irradiation stopped, but not in the video images. This probably means cavitation bubbles disappeared after the irradiation. This result indicates the necessity for the consideration of cavitaion effect on ultrasound diagnostic images in monitoring HIFU therapy.

  179. Design of Controller and its Servoing Performance of the Integrated System for Non-Invasive Ultrasound Diagnosis and Treatment

    小泉憲裕, 太田耕平, LEE Deukhee, 吉澤晋, 伊藤陽, 中島義和, 松本洋一郎, 光石衛

    日本ロボット学会学術講演会予稿集(CD-ROM)　24th　2006

  180. 3638 Simulation of Temperature Rise during High Intensity Focused Ultrasound Therapy

    KATO Mitsuaki, YOSHIZAWA Shin, ONO Kenji, MATSUMOTO Yoichiro

    The Proceedings of Mechanical Engineering Congress, Japan　2006　(0)　369-370　2006

    Publisher: 一般社団法人 日本機械学会

    DOI： 10.1299/jsmemecjo.2006.2.0_369 　

    More details Close

    Focused ultrasound treatment is widely applied in the clinical treatment, for example the tumor ablation with High Intensity Focused Ultrasound (HIFU). HIFU shows considerable nonlinearity due to its high pressure amplitude, and it is attenuated, reflected and refracted in the medium. Previously, researchers have simulated the ultrasound field using linear and nonlinear approximation equations. However, the predictions using these equations have restrictions such that the higher order nonlinearity or the reflection and refraction cannot be reproduced. So we apply axsymmetric Navier-Stokes equation to the governing equation to solve the ultrasound propagation without such restrictions. We calculated the profile of temperature rise in a liver with the model of an array transducer and an absorption effect. It is concluded that the temperature rise is focused at focal point by modeling array transducer and the ratio of the parameters inside the absorption coefficient affects the temperature rise and distribution.

  181. 2A1-A18 The development of the integrated system for non invasive ultrasound diagnosis and treatment (1st report) : The controller and experiment for servoing stone model in the bladder

    OTA Kohei, KOIZUMI Norihiro, YOSHIZAWA Shin, ITOH Akira, NAKAJIMA Yoshikazu, WARISAWA Shin'ichi, MATSUMOTO Yoichiro, MITSUISHI Mamoru

    The Proceedings of JSME annual Conference on Robotics and Mechatronics (Robomec)　2006　(0)　_2A1-A18_1-_2A1-A18_3　2006

    Publisher: The Japan Society of Mechanical Engineers

    DOI： 10.1299/jsmermd.2006._2A1-A18_1 　

    More details Close

    In this paper, the authors report the required functions of the integrated system for non invasive ultrasound diagnosis and treatment and the methods of mounting these functions. The concept of the proposed system is to destroy cancer tissues and stones by applying high intensity focused ultrasound (HIFU) to the affected parts precisely without destroying peritumoral tissues. But if the affected parts lie in the deep portion of the patient's body, it is difficult to apply HIFU precisely by reason of the movement of the affected parts with the influence of breath. Therefore the authors propose the system which has the function of canceling the influence of the movement.

  182. Medical applications in fluid mechanics (noninvasive therapeutic ultrasound with microbubbles)

    Y. Matsumoto, A. Fujiwara, S. Yoshizawa, Y. Kaneko

    Nagare　25　(6)　533-541　2006

    Publisher: Japan Society of Fluid Mechanics

    DOI： 10.11426/nagare1982.25.533 　

    ISSN：0286-3154

  183. Numerical study on growth by rectified diffusion of an oscillating bubble in an ultrasound field Peer-reviewed

    S. Yoshizawa, Y. Matsumoto

    Proc. of 6th International Symposium on Cavitation　2006

  184. Optimization of the bubble cloud collapse with application to lithotripsy Peer-reviewed

    T. Ikeda, S. Yoshizawa, Y. Matsumoto

    Proc. of 6th International Symposium on Cavitation　2006

  185. The design of microbubbles specialized for therapeutic or diagnostic use Peer-reviewed

    Yukio Kaneko, Shunsuke Watanabe, Shin Yoshizawa, Shu Takagi, Yoichiro Matsumoto

    AIP Conference Proceedings　754　224-226　2005/03/28

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.1901643 　

    ISSN：0094-243X

    eISSN：1551-7616

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    Medical applications which employ microbubbles, such as ultrasound imaging, gene transfer and sonodynamic therapy, are currently being investigated. In the field of bubble dynamics, it is known that bubbles can play a role in converting the mechanical energy of an ultrasound wave into not only energy of acoustic emission but also heat energy deposition when they are subjected to an oscillating field. In this study, the desired properties of the microbubble acting either as an echo source or a heat source are discussed. The type of gas inside a bubble has a strong effect on the energy radiation from the bubbles. It is shown that the balance between heat deposition and acoustic emission from the bubbles can be altered by changing the gas inside the bubbles. Consequently, HIFU treatment or ultrasound imaging can be carried out more effectively, utilizing these microbubbles. © 2005 American Institute of Physics.

  186. High-speed observation of two-frequency controlled cloud cavitation in HIFU field Peer-reviewed

    Teiichiro Ikeda, Masataka Tosaki, Shin Yoshizawa, Yoichiro Matsumoto

    AIP Conference Proceedings　754　199-203　2005/03/28

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.1901636 　

    ISSN：0094-243X

    eISSN：1551-7616

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    Ultrasound induced cavitation control with application to lithotripsy has been investigated. Previously, a two-frequency ultrasound combination has been proposed to utilize the violent collapse of the cloud cavitation. In this paper, the cavitation cloud collapse phenomena is investigated experimentally in more detail. The behaviour of the bubble cloud formation in the high frequency phase (3.88 [MHz]) is photographed. Then low frequency ultrasound (555 kHz, short pulse) is used to expose the various kinds of the cloud. Acoustic emission due to the bubble collapse is recorded with a Passive Cavitation Detector (PCD) and the response of the cloud to the 555 [kHz] ultrasound is investigated. © 2005 American Institute of Physics.

  187. Numerical study of the heat transfer from an oscillating bubble Peer-reviewed

    Shin Yoshizawa, John S. Allen, Shu Takagi, Yoichiro Matsumoto

    AIP Conference Proceedings　754　131-133　2005/03/28

    Publisher: AMER INST PHYSICS

    DOI： 10.1063/1.1901618 　

    ISSN：0094-243X

    eISSN：1551-7616

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    Recently, ultrasound contrast agents have been used for therapeutic purposes to enhance the heating effect of High Intensity Focused Ultrasound (HIFU). It has been shown that the heat transfer from the bubble is not negligible for medical ultrasound sound conditions. The heat transfer depends on the Peclet number and the shell properties of the bubble as well as the specific heat ratio of the internal gas. We investigate the heat transfer at various Peclet numbers, with or without a shell, numerically. The results show that there is an optimal Peclet number which corresponds to the maximum heat transfer from the bubble to the surrounding medium, and the viscous shell increases the thermal damping due to the heat generation in the shell. © 2005 American Institute of Physics.

  188. Nonlinear acoustic behavior of a microbubble in an oscillating pressure field

    S. Yoshizawa, Y. Matsumoto

    Nagare　24　(4)　405-412　2005

    Publisher: Japan Society of Fluid Mechanics

    DOI： 10.11426/nagare1982.24.405 　

    ISSN：0286-3154

  189. Dynamics of bubble and bubble cloud

    Y. Matsumoto, S. Yoshizawa

    Ultrasonic technology　17　(1)　1-6　2005

  190. Using of Focused Ultra-induced Cavitation Erosion for the Industrial Application

    TOSAKI Masataka, IKEDA Teiichiro, YOSHIZAWA Shin, TAKAGI Shu, MATSUMOTO Yoichiro

    Fluids engineering conference ...　2004　291-291　2004/11/24

    Publisher: The Japan Society of Mechanical Engineers

    ISSN：1348-2882

  191. Simulation of ultrasound propagation in body

    IMAKITA Akio, ONO Kenji, YOSHIZAWA Shin, MATSUMOTO Yoichiro

    Fluids engineering conference ...　2004　277-277　2004/11/24

    Publisher: The Japan Society of Mechanical Engineers

    ISSN：1348-2882

  192. Nonlinear oscillation of ultrasound contrast agents

    S. Yoshizawa, Y. Matsumoto

    Medical ultrasound - new technology and clinical application　125-129　2004

  193. Ultrasound Focusing in a Spherical Bubble Cloud Peer-reviewed

    S. Yoshizawa, T. Ikeda, S. Takagi, Y. Matsumoto

    Proc of the 5th International Conference on Multiphase Flow　2004

  194. Ultrasound Focusing in Spherical Bubble Cloud (CAV2003) Peer-reviewed

    S. Yoshizawa, Y. Matsumoto

    Proc. of Fifth International Symposium on Cavitation　2003

  195. Control of Cavitation in Ultrasound Field

    KANEKO Yukio, IKEDA Teiichiro, YOSHIZAWA Shin, TAKAGI Shu, MATSUMOTO Yoichiro

    The proceedings of the JSME annual meeting　2002　123-124　2002

    Publisher: The Japan Society of Mechanical Engineers

    DOI： 10.1299/jsmemecjo.2002.3.0_123 　

    More details Close

    It is known that cavitation erosion cause to break the parts of fluid machinery or damage the tissue of the body during medical ultrasound, for example, ESWL : Extracorporeal Shock Wave Lithotripsy. But if cavitation behavior can be analyzed and controlled actively, we are able to utilize cavitation as a transducer, which can concentrate energy in a very narrow area. And this cavitation control has the possibilities to be applied in engineering and medical field. In order to analyze cavitation behavior in ultrasound field, we conduct experiments and numerically simulate the dynamics of bubble cloud in detail, and we obtain the following conclusions. We build the method to concentrate cavitation cloud only in a small region with high frequency ultrasound and oscillate and crush the cloud with low frequency one near the natural frequency of it. And it is possible to break an object in a narrow area by this method.

  196. Nonlinear oscillation of a bubble

    Y. Matsumoto, S. Yoshizawa

    Science of machine　54　(1)　108-113　2002

  197. Acoustic Emission from Micro Bubbles in Ultrasound Field Peer-reviewed

    S. Yoshizawa, K. Sugiyama, Y. Matsumoto

    Proc. of Fourth International Symposium on Cavitation　2001

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Books and Other Publications 4

  1. Ultrasonics : physics and applications

    Matsukawa, Mami

    IOP Pub.　2022

    ISBN: 9780750349345

  2. スマート医療テクノロジー

    エヌ・ティー・エス　2019/10

    ISBN: 9784860436193

  3. 微細気泡の最新技術Vol.2 ～進展するマイクロ・ナノバブルの基礎研究と拡がる産業利用～

    エヌ・ティー・エス　2014/08

    ISBN: 9784860434076

  4. マイクロバブル最前線

    松本洋一郎, 高木周, 吉澤晋, 金子暁子, 竹村文男, 村井祐一, 川村隆文, 児玉良明, 幸田和郎, 井田博之, 川崎達治, 金子幸生

    共立出版　2009

    ISBN: 9784320081673

Presentations 14

  1. Enhancement of cavitation inception by second-harmonic superimposition International-presentation

    S. Yoshizawa, R. Takagi, J. Yasuda, S. Umemura

    19th International Symposium on Nonlinear Acoustics　2012/05/21

  2. High-intensity focused ultrasound heating of large tissue region enhanced by cavitation bubbles at multiple focal spots

    S. Yoshizawa, K. Nakamura, A. Asai, J. Yasuda, S. Umemura

    Acoustics 2012　2012/05/13

  3. Ultrasound Tissue Heating Enhanced by Cavitation Clouds at Multiple Focal Spots for High-intensity Focused Ultrasound Therapy International-presentation

    S. Yoshizawa, T. Moriyama, E. Iwasaki, K. Nakamura, A. Asai, S. Umemura

    6th International Symposium on Medical, Bio- and Nano-Electronics　2012/03/08

  4. Cavitation Inception and Growth by Dual-Frequency Excitation in High-Intensity Focused Ultrasound Treatment International-presentation

    S. Yoshizawa, J. Yasuda, S. Umemura

    2011 IEEE International Ultrasonics Symposium　2011/10/18

  5. Cavitation Inception and Growth by Dual-Frequency Excitation Method International-presentation

    S. Yoshizawa, R. Takagi, J. Yasuda, S. Umemura

    11th International Symposium on Therapeutic Ultrasound　2011/04/11

  6. Large-volume coagulation by creating multiple cavitation clouds in High Intensity Focused Ultrasound treatment International-presentation

    S. Yoshizawa, Y. Inaba, R. Takagi, S. Umemura, Y. Muragaki, H. Iseki

    Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) International Symposium　2011/01/17

  7. 3D reconstruction of ultrasonic fields from optical measurement International-presentation

    R. Omura, Y. Shimazaki, ○S. Yoshizawa, S. Umemura

    2010 IEEE International Ultrasonics Symposium　2010/10/11

  8. Ultrasound lithotripsy for pet kidney stones International-presentation

    S. Yoshizawa, K. Iida, A. Wada, T. Matsuura, H. Ishii, S. Umemura, Y. Matsumoto

    10th International Symposium on Therapeutic Ultrasound　2010/06/09

  9. Enhancement of Localized Heating by Creating Multiple Cavitation Clouds International-presentation

    S. Yoshizawa, Y. Inaba, R. Takagi, S. Umemura

    10th International Symposium on Therapeutic Ultrasound　2010/06/09

  10. Tissue ablation using cavitating bubbles triggered by high intensity ultrasound pulse International-presentation

    S. Yoshizawa, R. Takagi, S. Umemura

    9th International Symposium on Therapeutic Ultrasound　2009/09/23

  11. Cavitation Detection with Subharmonic Emissions by Low Intensity Sustaining Ultrasound International-presentation

    S. Yoshizawa, S. Umemura, Y. Matsumoto

    2008 IEEE International Ultrasonics Symposium　2008/11/02

  12. Ultrasound Heating Enhanced with Acoustic Cavitation Induced by Pulsed Ultrasound International-presentation

    S. Yoshizawa, S. Umemura, Y. Matsumoto

    8th International Symposium on Therapeutic Ultrasound　2008/09/10

  13. High Intensity Focused Ultrasound Therapy with Microbubbles International-presentation

    S. Yoshizawa, S. Umemura, Y. Matsumoto

    11th International Symposium on Advanced Biomedical Ultrasound　2008/03/07

  14. Numerical Study on Rectified Diffusion of an Oscillating Microbubble in an Ultrasound Field International-presentation

    S. Yoshizawa, Y. Matsumoto

    1st International Colloquium on Dynamics, Physics and Chemistry of Bubble and Gas-Liquid Boundaries　2007/09/25

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Industrial Property Rights 15

  1. 超音波医用装置

    吉澤 晋, 高木 亮, 梅村 晋一郎, 玉野 聡

    特許6633314

    Property Type: Patent

  2. 光音響計測装置

    長岡 亮, 西條 芳文, 梅村 晋一郎, 吉澤 晋

    Property Type: Patent

  3. 超音波医用システム

    吉澤 晋, 高木 亮, 梅村 晋一郎, 玉野 聡

    Property Type: Patent

  4. 超音波の送信回路

    梅村 晋一郎, 吉澤 晋, 神保 勇人, 玉野 聡

    Property Type: Patent

  5. アレイ型超音波送波器

    梅村 晋一郎, 吉澤 晋, 大津 賢治

    Property Type: Patent

  6. アレイ型超音波送波器

    梅村 晋一郎, 吉澤 晋, 大津 賢治

    特許第5605567号

    Property Type: Patent

  7. 超音波洗浄方法

    正木 広志, 妻木 伸夫, 佐原 輝隆, 北田 由光, 松本 洋一郎, 吉澤 晋

    Property Type: Patent

  8. 超音波洗浄方法

    正木 広志, 妻木 伸夫, 佐原 輝隆, 北田 由光, 松本 洋一郎, 吉澤 晋

    特許第5127257号

    Property Type: Patent

  9. 超音波洗浄装置

    松本 洋一郎, 池田 貞一郎, 吉澤 晋, 佐原 輝隆, 妻木 伸夫, 北田 由光

    Property Type: Patent

  10. 超音波洗浄装置

    松本 洋一郎, 池田 貞一郎, 吉澤 晋, 佐原 輝隆, 妻木 伸夫, 北田 由光

    特許第4442383号

    Property Type: Patent

  11. 超音波照射方法及び超音波照射装置

    松本 洋一郎, 池田 貞一郎, 吉澤 晋

    Property Type: Patent

  12. 超音波照射方法及び超音波照射装置

    吉澤 晋, 松本 洋一郎, 池田 貞一郎

    Property Type: Patent

  13. 超音波照射方法及び超音波照射装置

    吉澤 晋, 松本 洋一郎, 池田 貞一郎

    特許第4139916号

    Property Type: Patent

  14. 微小可動機構システムと微小可動機構部の制御方法

    柳田 美穂, 吉澤 晋

    Property Type: Patent

  15. 微小可動機構システムと微小可動機構部の制御方法

    柳田 美穂, 吉澤 晋

    特許第3800161号

    Property Type: Patent

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Research Projects 15

  1. Ultrasonic signed echo imaging to distinguish bwtween vulnerable and stable plaques

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (C)

    Institution: Tohoku University

    2021/04/01 - 2024/03/31

  2. リピッドバブルとMRIガイド経頭蓋超音波による血液脳関門開口と脳内薬物送達

    丸山 一雄, 吉田 道春, 梅村 晋一郎, 吉澤 晋, 小俣 大樹

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 基盤研究(B)

    Institution: 帝京大学

    2020/04/01 - 2023/03/31

    More details Close

    脳には血液と脳実質の間の物質移行を厳密に制御する血液脳関門が存在する。脳腫瘍やアルツハイマー病などの中枢神経系疾患に対する薬物治療において、血液脳関門が障壁となる。そのため、脳実質へと薬物送達可能な技術が求められている。近年、集束超音波とマイクロバブルを利用した血液脳関門の透過性亢進技術が注目されている。超音波照射によりマイクロバブルの収縮や膨張といった機械的作用が誘導され、血管内皮細胞間の密着結合が緩まり、血管透過性が亢進すると考えられている。そのため、マイクロバブルの収縮や膨張などの振る舞いに影響する超音波の周波数と音圧は、血液脳関門の透過性亢進において重要なパラメーターである。そこで本研究では、効率的かつ低侵襲的な血液脳関門の透過性亢進を行うために、脳への薬物送達と傷害性に及ぼす集束超音波の周波数と音圧の影響を検討した。マウスにリピッドバブルとモデル薬物としてエバンスブルーを静脈内投与し、脳に集束超音波 (周波数：0.25, 0.5, 1.0 MHz、音圧：0.1, 0.2, 0.4, 0.6 MPa) を照射した。1時間後に血液還流し、脳実質へのエバンスブルー移行を評価した。その結果、0.25 MHz、0.5 MHzの各音圧および1 MHzの0.6 MPaでは脳の広範囲において脳の広範囲においてエバンスブルーの漏出が認められた。一方で、1 MHzの0.4 MPaでは超音波集束部位でエバンスブルーの漏出が認められた。次に、各周波数において、エバンスブルー漏出が認められた最低音圧を用いて、血液脳関門の透過性亢進を誘導し、脳切片のヘマトキシリン・エオジン染色により傷害性を評価した。その結果、0.25 MHzと0.5 MHzでは赤血球の漏出が認められたに対して、1 MHzの0.4 MPaでは赤血球の漏出は認められなかった。これらの結果から、1 MHz、0.4 MPaの集束超音波照射条件を用いることで、標的部位に対して低侵襲的かつ効率的な血液脳関門オープニングを誘導できることが示唆された。

  3. 音響力学的療法における治療効果増強薬剤の探索的研究

    岡本 淳, 吉澤 晋, 村垣 善浩

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 基盤研究(B)

    Institution: 東京女子医科大学

    2020/04/01 - 2023/03/31

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    本提案では音響力学的療法（sonodynamic therapy：SDT）において抗腫瘍効果増大作用を示す薬剤の網羅的な探索研究を行う。SDTは高密度集束超音波（high-intensity focused ultrasound: HIFU）と薬剤の相互作用を利用する方法であり、体内深部の低侵襲がん治療を目的としている。我々は既にDDS製剤（エピルビシンナノミセル）を用いたSDTの疾患動物治療や人に対する臨床研究を行っているが、SDTの作用機序自体は明らかでない部分が多い。本研究では難治性がんの代表である膵がん等で適用されている抗がん剤を中心に選定した薬剤に対し、HIFUとの相互作用によるマウスに対する腫瘍増殖抑制効果検証実験を行い、がんに対して有効な薬剤のスクリーニングを行うとともに、結果から推測される作用機序について考察を行い、SDTの効果に関する科学的な説明を試みる。 本年度は効果的にキャビテーションをエンハンス可能なマルチチャンネルトランスデューサを開発し、性能評価試験を実施した。加熱波、トリガー波の焦点サイズと焦点位置、サイドローブの大きさを精密に測定し、また、天秤法により音響出力も正確に測定を行った。さらに焦点温度の計測も行い、細胞に対するサーマルドーズとの関係を導き、細胞への影響を定量化した。来年度以降、本トランスデューサを用い、マウス等を用いたSDT実験を実施していく。

  4. 超音波キャビテーションを利用した高速・高精度な超音波結石破砕法の開発

    吉澤 晋, 梅村 晋一郎

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業 基盤研究(B)

    Category: 基盤研究(B)

    Institution: 東北大学

    2016/04/01 - 2020/03/31

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    1. 開発したトランスデューサの評価 前年度に開発したトランスデューサの評価を行った．開発したトランスデューサは，0.5 MHz付近と1 MHz付近の2周波数で共振するように設計した．測定の結果，128素子平均での共振周波数は0.48 MHzと0.93 MHzとなった．また，0.48 MHzおよび0.50 MHzにおけるコンダクタンスはそれぞれ2.0 mSおよび1.7 mSとなった．従って，音響エネルギー変換効率が70%程度であるとすると，400 Vpp駆動で3～4 kW程度の音響出力が可能である．音響出力としては，先行研究である0.17 MHzのBurst wave lithotripsy（BWL）を上回ると考えられる． 2. 様々な超音波照射方法による結石破砕実験 さらなる結石破砕の高速化を目指し，まずは周波数1 MHzの強力な超音波を照射し，モデル結石の破砕実験を行った．モデル結石の材料としては，従来のセメントから歯科用石膏に変更した．石膏はモデル結石破砕実験でセメントよりも一般的に用いられる材料であり，セメントに比べて均質性の高いモデル結石ができる．作成したモデル結石のビッカース硬さを測定したところ，平均値が102 HV，標準偏差が14 HVであった．ばらつきはセメントで作成したときよりも改善しており，値は同程度で硬い結石のビッカース硬さと同程度であった．このモデル結石に対して，結石サイズと同等程度の円環状の焦点パターンを持つ超音波を照射し，破砕実験を行った．しかしながら，破砕効率（破砕速度を入力音響エネルギーで割ったもの）は向上しなかった．

  5. Hemi-sperical ultrasonic trasducer producing high power at low voltage

    Umemura Shin-ichiro, ITO HIROSHI

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Tohoku University

    2016/04/01 - 2019/03/31

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    A short ultrasonic pulse at an extremely high pressure is effective to generate acoustic cavitation, which remarkably enhances the efficiency of ultrasonic therapy and lithotripsy. However, if it is for a conventional thickness mode piezoelectric transducer, the required driving voltage may almost exceed the limit of MOSFETs. To overcome this problem, we have suggested a spherical transducer utilizing the co-resonance between a piezoelectric spherical shell and a water sphere. We are further suggesting a cylindrical transducer utilizing the co-resonance between a piezoelectric cylindrical shell and a water cylinder. Its principle was confirmed by a numerical simulation, and a prototype transducer was constructed, which proved that the ratio of acoustic output / driving voltage was in a realistic range.

  6. High-speed Measurement of 3D Ultrasound Field Reconstructed from Shadowgraph Images

    YOSHIZAWA Shin

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

    Category: Grant-in-Aid for Challenging Exploratory Research

    Institution: Tohoku University

    2016/04/01 - 2019/03/31

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    An experimental system for the measurement of a 3D ultrasound field reconstructed from optical images was developed. The optical images of a 3D focused ultrasound field were obtained and the pressure field was successfully reconstructed. A simulation code was developed to estimate optical phase modulations by acoustic field from shadowgraph images. The error of the reconstructed pressure when the distance between the acoustic field and the optical measurement plane was relatively long was reduced by the simulation. Furthermore, a 3D ultrasound field was reconstructed using the combination of the optical measurement and numerical simulation where the nonlinearity of ultrasound propagation is considered. The measurement time for a 3D nonlinear ultrasound field was significantly reduced by the combined method.

  7. Development of photoacoustic flow cytometry by employing multi-channel high frequency ultrasonic probe

    Nagaoka Ryo, SAIJO Yoshifumi, UMEMURA Shin-ichiro, YOSHIZAWA Shin, ARAKAWA Mototaka, ISHIKAWA Kazuo

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Research Activity start-up

    Category: Grant-in-Aid for Research Activity start-up

    2016/08/26 - 2018/03/31

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    In a traditional photoacoustic flow cytometry, cells in vessels are aligned in one line by laser manipulation, and the photoacoustic signals induced from the cells are measured to classify the characteristics. However, scattering and absorption in the living tissues has effects on the propagation of the radiated laser, and the alignment of the cell by the manipulation cannot be achieved owing to the effect. In this study, the effect of the scattering and absorption was minimized by acoustical focusing, and the method could visualize the living tissues at the deeper part was developed.

  8. Real-time detection of HIFU (high-intensity focused ultrasound) induced thermal coaulation by ultrasonic imaging

    Umemura Shin-ichiro, YOSHIZAWA SHIN

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Tohoku University

    2013/04/01 - 2016/03/31

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    In noninvasive therapy such as HIFU (high-intensity focused ultrasound) treatment, a noninvasive imaging method to aim and monitor the tissue to be treated is essential because the surgeon cannot looked at the tissue by naked eye. Ultrasonic imaging has advantages that the deflection due to non-uniformity in sound speed can be inherently corrected and that real-time imaging can achieved at a relatively low cost, but temperature mapping is significantly more difficult than MRI in principle. Therefore, we looked at the fact that the correlation between ultrasonic echo images before and after thermal coagulation significantly decreases because of the change in backscatter of the tissue. As the result of this study, we succeeded in real-time detection of HIFU-induced thermal coagulation of tissue by real-time mapping of maximum correlation coefficient between the ultrasonic RF images obtained using high-speed ultrasonic imaging.

  9. Treatment Time Reduction in Ultrasound Thermal Therapy using Cavitation Bubbles in a Large Region

    YOSHIZAWA Shin, UMEMURA Shin-ichiro

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Tohoku University

    2012/04/01 - 2015/03/31

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    High-intensity focused ultrasound has attracted much attention as a modality for the noninvasive thermal treatment of cancer. However, it has a problem of long treatment time. The objective of this study is to develop a method for the ultrasonic heating with high efficiency by using cavitation clouds generated in a large region. Cavitation clouds were generated and used in a large region by electronically scanning HIFU focus in a plane perpendicular to the HIFU propagation direction. Applying this method to a tissue mimicking phantom, the temperature rise measured with a thermocouple was two to three times of that without cavitation generation. The coagulation volume of chicken breast tissues showed a high efficiency of the developed method for a HIFU thermal treatment.

  10. ACCELERATION OF FOCUSED ULTRASOUND TREATMENT BY HIGH-INTENSITY TRIGGER PULSES

    UMEMURA Shinichiro, YOSHIZAWA Shin

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Tohoku University

    2010 - 2012

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    The generation of cavitated microbubbles which can potentially enhance ultrasonic heating of biological tissue was studied using a high-speed camera. An optically transparent gel with tissue-mimicking ultrasonic properties was developed and used. The generation was confirmed at an ultrasonic intensity more than the order of 10 kW/cm2. It was localized in the focal region at a pulse duration less than the order of 100 μs. The throughput of ultrasonic thermal coagulation of excised tissue was markedly improved by the generated microbubbles. Furthermore, it was discovered that the ultrasonic intensity needed for generating such cavitated microbubbles can be significantly reduced by superimposing the second harmonic to the fundamental.

  11. Development of a novel method to enhance localized heating by cavitation bubbles for ultrasound cancer treatment

    YOSHIZAWA Shin

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

    Category: Grant-in-Aid for Young Scientists (B)

    Institution: Tohoku University

    2010 - 2011

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    High-intensity focused ultrasound (HIFU)therapy is attracting attention as a noninvasive therapeutic modality for cancer. However, it has a problem of long treatment time. It is known that acoustic cavitation generated in the focal region of HIFU enhances tissue heating. In this study, the behavior of cavitation bubbles were observed and scattered pressure waves from the bubbles were detected and investigated for the cavitation monitoring. The optical pressure measurement method was also investigated.

  12. Development of a method to control acoustic cavitation withdual-frequency ultrasound for therapeutic use

    YOSHIZAWA Shin

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

    Category: Grant-in-Aid for Young Scientists (B)

    Institution: Tohoku University

    2008 - 2009

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    Ultrasound treatment has attracted much attention as a treatment for cancer, and many researchers have investigated the method. One of the big topics of the investigation is to control of cavitation bubbles induced by therapeutic ultrasound. In this study, dual-frequency method was investigated to generate cavitation with lower intensity ultrasound and control the cavitation bubbles. The results showed that it is important to choose the frequency and the phase difference of the two-frequency ultrasound depending on the properties of the bubbles.

  13. Noninvasive High Intensity Focused Ultrasound Therapy with Microbubbles Competitive

    2007/05 -

  14. 集束超音波音場における微小気泡群のマルチ・スケール解析およびその医療応用

    吉澤 晋

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業 特別研究員奨励費

    Category: 特別研究員奨励費

    Institution: 東北大学

    2007 - 2007

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    本年度の研究においては,強力集束超音波による非侵襲治療を目指して,集束超音波音場における微小気泡および微小気泡群のマルチ・スケール解析を実験・数値計算によって調べた. 医療応用を目的とした実験的な研究としては,動物実験に適用可能な治療システムとして,呼吸による臓器移動を補正しつつキャビテーション気泡群を制御するシステムを構築した.この成果は,「J. Robotics Mechatronics」にて発表された.単一球形気泡の体積振動に関しては,Rectified diffusionによる気泡成長について詳しく調べた.直接数値計算による非線形な挙動と,単純化されたモデルによる結果の比較を行うことで直接数値計算の重要性を調べた.また直接数値計算によって,用いる超音波波形や気泡の大きさについての様々な条件下でRectified diffusionによる気泡成長について調べ,その結果を「1st International Colloquium on Dynamics,Physics and Chemistry of Bubble and Gas-Liquid Boundaries」において発表した.また,単一気泡での解析結果を気泡群の数値解析にフィードバックし,気泡群の数値解析に改良を加えた.その気泡群数値解析コードによる結果の一部を「11th International Symposium on Advanced Biomedical Ultrasound」において発表を行った.

  15. 強力集束超音波による非観血的低侵襲治療システムの構築

    吉澤 晋

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業 特別研究員奨励費

    Category: 特別研究員奨励費

    Institution: 東京大学

    2004 - 2006

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    単一球形気泡の体積振動に関しては,「6th International Symposium on Cavitation」において気泡振動におけるrectified diffusionにつていの発表を行った.ここでは,昨年度に構築したモデルによる計算結果について従来の近似式によって求められる量との比較検討を行ったうえで,異なる2種類の周波数の超音波を重畳させた波形を用いた計算を行い,その波形,圧力振幅とrectified diffusionによるガスの輸送量について詳細な解析を行った.その結果として,周波数重畳波形がガスの輸送を促進させることのできる気泡の大きさについての知見を得た.気泡群の挙動については,昨年度に日本機械学会論文集に掲載されたものをさらに推し進め,波形や気泡のプロパティをパラメータとした計算を行い,それらの結果をまとめて「151^<st> Meeting Acoustic Society of America」において発表を行った.ここでは,マイクロサイズの微小気泡からなる球形気泡クラウドの周波数応答や,気泡クラウドが崩壊するときの気泡の挙動について,昨年度まででわかったことに加えて,波形や気泡のプロパティを変えることによる定量的な影響についての知見が得られるとともに,崩壊挙動の機序や周波数応答の性質については違いがないことがわかった. 実験では,昨年度に行ったブタ膀胱内でのモデル結石の破砕実験の結果を踏まえて,動物実験において体内のキャビテーション発生,成長をモニタリングし,それによってそのときの実験における適切な超音波のパラメータを決定する手法を水槽実験において開発した.また,それまでの超音波結石破砕にかかる成果は「Ultrasound Medicine and Biology」誌に論文が掲載された.

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