Abstract Previously, we proposed an ultrasonic measurement method of arterial wall elasticity for the early detection of arteriosclerosis. Since vascular wall elasticity depends on blood pressure, in this study, the elasticity and viscosity were estimated using the hysteresis loop determined between the incremental strain in the wall and internal pressure by altering the internal pressure in the phantom and in vivo experiments. Consequently, both the estimated elasticity and viscosity increased with the internal pressure. Moreover, the slope of each hysteresis loop was larger than that of the approximated curve for the lowest blood pressures of the hysteresis loops with different internal pressures, as the blood pressure changed in the order of several hertz within a single heartbeat. Hence, we conclude that measuring both the blood pressure and the elastic and viscous moduli would be beneficial in comprehensively investigating more vessel wall properties that change with the progression of arteriosclerosis.

Abstract The thickness of the carotid arterial wall obtained from B-mode imaging using ultrasonic diagnostic devices is widely used for the diagnosis of atherosclerosis. However, the measurement interval in the lateral direction of the B-mode image depended on the beam interval (>100 μm). Therefore, the B-mode image is discrete in the lateral direction and cannot reflect changes in local and minute thicknesses. A method for measuring the roughness of the luminal surface of the wall was proposed using the displacement of the carotid arterial wall in the lateral direction during one heartbeat. In this method, the lateral measurement interval is much shorter than the beam interval, enabling a smooth measurement of the luminal surface. By simultaneously applying the method to the lumen-intima and medial-adventitia boundaries of the wall, we propose a novel method to measure the local and minute thicknesses of the carotid arterial wall.

Quantification of the dynamics of the carotid artery wall is useful in evaluating arteriosclerosis and atherosclerosis. As the carotid artery wall moves not only in the radial direction but also in the longitudinal direction, longitudinal movement should be considered in the analysis of the dynamic properties of the carotid artery wall. In this study, we propose a "lateral M-mode" method for visualizing the longitudinal movement of the intima-media complex (IMC). For the lateral M-mode, we set the target line in the longitudinal direction along the IMC and visualize the signals on the target line frame-by-frame by correcting the position of the target line along the radial displacement estimated by the phased tracking method. Differentiating the envelope signals between consecutive ultrasound beams was effective in visualizing the lateral movement of the IMC. The precision of the longitudinal displacement of the IMC estimated using the conventional block-matching method was validated by comparing it with the lateral M-mode. Because the conventional M-mode sequence plays an important role in evaluation of the dynamics of various tissues, the proposed "lateral M-mode" contributes to a detailed understanding of vascular dynamics and the development of diagnostic methods for vascular diseases.

In this study, the attenuation coefficient of blood was measured in vivo in the frequency range of 10–45 MHz. A procedure to correct the distribution of sound pressure in the measurements was discussed. Further, in vivo measurements were applied on the dorsal hand vein of four healthy subjects at rest and during avascularization. As a preliminary result, less variation of the measured attenuation coefficients was achieved by the proposed method. The comparable results of the inclination of the attenuation coefficients were obtained at rest and during avascularization. Furthermore, the attenuation coefficients during avascularization were markedly higher than those at rest, reflecting the degree of red blood cell aggregation promoted by avascularization. This method may aid in the non-invasive evaluation of blood properties reflecting the degree of red blood cell aggregation.

For the early diagnosis of atherosclerosis, our group developed an ultrasound probe that can simultaneously measure blood pressure and vessel diameter at the same position. However, because the developed probe requires the blood vessel to be deformed by pushing to measure the blood pressure, it affects the estimation of the vessel's elastic modulus. In the present study, we derived a series of equations to estimate the elastic modulus of a blood vessel considering the pushing pressure applied by the ultrasound probe and the resultant deformation of the blood vessel. The validity of the proposed method was verified by numerical calculations, and then the method was applied to in vivo measurements. The proposed method resulted in fewer variations in the elastic modulus estimates with different pushing pressures compared with the conventional method.

In epidural anesthesia, it is difficult to specify the puncture position of the anesthesia needle. We have proposed an ultrasonic method to depict the thoracic spine using the different characteristics of reflection from bone and scattering from muscle tissue. In the present paper, we investigated the transmission aperture's width of the ultrasound probe to emphasize the differences in the reflection and scattering characteristics. First, we determined the optimum transmission aperture's width using a simulation experiment. Next, we measured reflection and scattering signals by changing the transmission aperture's width in a water tank experiment and confirmed that the results corresponded to the simulations. However, as the transmission aperture's width increased, the lateral resolution at the focal point improved. Therefore, better imaging of the human thoracic vertebrae can be achieved by selecting the transmission aperture's width, which considers the effect on lateral resolution.

Improving spatial resolution is a crucial issue in medical ultrasound. One of the improving methods is the post-processing of the received ultrasound RF signal. In the present paper, we proposed a design method for a noise-robust broadband filter based on the singular value decomposition of the received RF signal. To design a noise-robust filter, we proposed a logical method to determine the optimal truncated order of singular values, which was validated by applying the filter to noise-contaminated signals. Furthermore, the proposed filter applied to the wire phantom resulted in a better axial resolution than that obtained without the filter and with our previously designed Wiener filter.

Noninvasive measurement of the degree of red blood cell (RBC) aggregation is useful for evaluating blood properties. In the present paper, we proposed a method to estimate the size of RBC aggregates without using the power spectrum of the posterior wall by introducing a reference scattering spectrum. The reference power spectra were calculated using the power spectrum measured for an ultrafine wire with a hemispherical tip. They were applied to the size estimation of microparticles simulating RBC aggregates. The estimated sizes were close to the true values, which shows that the calculated reference power spectra were suitable for accurate size estimation. The proposed method was also applied to in vivo measurements, and the estimated sizes between at rest and in RBCs aggregated by avascularization were successfully differentiated. This demonstrates that the proposed method will be useful for estimating the size of RBC aggregates.

The heart wall has a multilayered structure and moves rapidly during ejection and rapid filling periods. Local strain rate (SR) measurements of each myocardial layer can contribute to accurate and sensitive evaluations of myocardial function. However, ultrasound-based velocity estimators using a single-frequency phase difference cannot realize these measurements owing to insufficient maximum detectable velocity, which is limited by a quadrature frequency. We previously proposed a velocity estimator using multifrequency phase differences to improve the maximum detectable velocity. However, the improvement is affected by a spatial discrete Fourier transform (DFT) window length that represents the locality of the velocity estimation. In this article, we theoretically describe that shortening the window increases the interference between different frequency components and decreases the maximum detectable velocity. The tradeoff between the maximum detectable velocity and the window length was confirmed through simulations and a water-tank experiment. Under the tradeoff, the Hanning window, which was used in previous studies, is not always appropriate for the local measurement of the velocity, which sometimes exceeds 100 mm [Formula: see text] depending on the subject, direction of the ultrasound beam to the heart wall, and cardiac periods. In the in vivo measurement with the short window, the Tukey window with a large flat part that has a high-frequency resolution and ameliorates the discontinuity at both edges of the windowed signal was appropriate to measure the maximum velocity. This study offers the potential for local measurements of each myocardial layer using the multifrequency velocity estimator with the appropriate window function and window length.

目的:医用超音波は,硬膜外麻酔時の穿刺位置の特定に用いられている.しかし,胸椎の構造は複雑であり,胸椎と筋組織の描出の区別は難しい.本研究では,超音波の反射・散乱特性の差異に基づき,骨と筋組織の描出を区別することを目的とする.方法:骨と筋組織からの受信信号の差を実験的に調べた.骨を強調するための新しいパラメータとして,理想的な遅延線上のみの受信信号の振幅と,その周囲の広い範囲における受信信号の平均振幅との比を提案した.結果:はじめに,基礎実験により,骨と筋組織からの受信信号の差を確認した.また,トリもも肉を用いたin vitro実験,ヒトにおけるin vivo実験により,その差を確認した.両実験において,提案法は,通常のBモード像と比較して,骨の描出を強調し,筋組織の描出を抑制することに成功した.結論:骨からの反射特性と筋組織からの散乱特性の差を用いて,提案法により,骨と筋組織を区別することができた.(著者抄録)

Measurement of the myocardial strain rate (SR), with high spatial resolution, is useful in evaluation of the transmurality of myocardial infarction. As the SR distribution is calculated using velocities observed at multiple positions in the heart wall, it is necessary to estimate the local velocity to measure SR distribution. In the present study, our previously proposed local velocity estimator, with multifrequency phase differences, was used to measure SR distribution in the heart wall. The SR distribution measured with the proposed local velocity estimator revealed alternate layers of contraction and relaxation, which were not measured with the conventional velocity estimator with spatial averaging. The reproducibility of the SR distributions was confirmed in three consecutive heartbeats with three subjects. High-spatial-resolution SR measurement with the proposed local velocity estimator will allow myocardial layer-specific analysis in the transmural direction.

The quality of ultrasonic images can be improved by estimating the sound velocity accurately. Our previous study proposed a method to estimate the sound velocity based on the difference between the reception times of radiofrequency signals received by elements in an ultrasonic probe. Because the method assumed an ideal point scatterer as the target, the estimation error in the sound velocity increased with an increase in the target scatterer size. In the present study, the effect of the target scatterer size on the estimation method was examined, and the relationship between the size of the target scatterer and the estimation error in the sound velocity was quantified. Through simulations and basic experiments, it was confirmed that the estimation error was caused by the change in the reception time from the target surface and that the estimation error depended on the depth and size of the target scatterer.

A sharp depiction of the puncture point of the needle by differentiating muscle and bone is required for ultrasound-guided epidural anesthesia in the thoracic spine. In the present paper, we proposed a method for depicting the thoracic vertebral surface by utilizing the difference between scattering and reflection characteristics. This method estimates whether an object is a scatterer or a reflector referring to the scattering and reflection characteristics acquired in the water tank experiment. The proposed method was applied to basic experiments and in vivo experiments. In the basic experiments, the matching using root mean squared error allowed us to differentiate the depiction between scattering and reflection. In the in vivo experiment, we were able to estimate the position of the bone as a reflector and the slope was generally correct.

Purpose: In coherence-based beamforming (CBB) using a generalized coherence factor (GCF), unnecessary signals caused by sidelobes are reduced, and an excellent contrast-to-noise ratio (CNR) is achieved in ultrasound imaging. However, the GCF computation is complex compared to the standard delay-and-sum (DAS) beamforming. In the present study, we propose a method that significantly reduces the number of GCF computations. Methods: In the previously proposed GCFreal, generation of the analytic signal for each element in the conventional GCF could be omitted. Furthermore, in GCF estimated from binarized signals (GCFB) proposed in the present study, the GCF value is calculated after the received signal of each element is binarized to reduce the computational complexity of the GCF. Results: The values of GCFB and GCFreal estimated from simulation and experimental data were compared. We also evaluated the image quality of B-mode images weighted by GCFB and GCFreal. Compared with GCFreal, GCFB was superior in reducing unnecessary signals but tended to reduce the brightness of the diffused scattering media. The CNR improvement was comparable for both methods. Conclusion: Generalized coherence factor estimated from binarized signals exhibits excellent CNR improvement compared to DAS. CNR improvements yielded by GCFB and GCFreal may depend on the observation target; however, under the conditions of the present study, comparable performances were obtained. Because GCFB can significantly reduce the computational complexity, it is potentially applicable in clinical diagnostic equipment.

Red blood cell (RBC) aggregation is the reversible adhesion of RBCs among themselves. We previously reported a positive correlation between blood glucose level and the degree of RBC aggregation (the brightness of the B-mode image). In the present study, we investigated the contribution to the brightness according to the deviation from the central axis in measurements along with the long-axis view of the vein. The results show that the brightness changed significantly for a slight change in the lateral position in the short-axis image. We found that the stability of the measurements was not guaranteed in the long-axis view and estimated the correct analysis window range for the short-axis view.

Studies to investigate the ultrasound elasticity measurement of the carotid artery, for early detection of arteriosclerosis, are ongoing. In the long-axis cross-sectional measurement in vivo, the position where the intima-media complex (IMC) is visible on the B-mode image was assumed to be the central axis of the short-axis view of the carotid artery. However, the IMC is also visible near the central axis of the short-axis view of the carotid artery. In the present study, accuracy in elasticity measurement within the IMC visible range was evaluated through a phantom experiment. The elasticities of the posterior wall measured at plural points within the IMC visible range differed by up to 6%. From the experimental results, we concluded that for the highest accuracy, it is important to measure along the central axis of the short-axis view of the carotid artery.

A measurement by transmitting ultrasonic non-focusing beams increases the temporal resolution but causes an error in the velocity measurements because of the lower signal-to-noise ratio (SNR) caused by the lower transmitted power and the lower spatial resolution. In the present study, we evaluated the relationship between the SNR and the transmitted beamwidth by the phantom experiment. The SNR decreased as the beamwidth became wider, and the measurement error increased when SNR was lower than 10 dB. Furthermore, the error factor due to the low spatial resolution more affected the measurement error than that due to the low transmitted power.

We developed a single ultrasound probe to simultaneously measure blood pressure and changes in the diameter of the radial artery to estimate the wall viscoelasticity during flow-mediated dilatation (FMD). This probe can be used for the early diagnosis of arteriosclerosis. This paper introduces the pulse transit time method to accurately measure changes in blood pressure during FMD. Using the single ultrasound probe and the proposed method, in vivo experiments involving three subjects were conducted, and reasonable results on blood pressure were obtained. Thus, the usefulness of the pulse transit time method was experimentally confirmed.

The in vivo measurement of the contractile response caused by electrical excitation has been studied to detect myocardial ischemia in its early stages. In the present study, we used our previously proposed local velocity estimator to measure the two-dimensional distribution of the strain rate using high-density beam scanning to obtain propagation of the local and minute contractile response in the heart walls of healthy humans. Alternate layers of contraction and relaxation were observed around the time phase representing the onset of the conduction of electrical excitation. The contraction propagated along the direction of the myocardial fiber in the myocardial layer. These results indicated that the electrical excitation conducted in each myocardial layer and the transmural shearing deformation occurred at the boundary between alternate layers of contraction and relaxation. The measurement of the propagation of the local and minute contractile response can reveal the effective contraction with the transmural shearing deformation.

© 2020 World Federation for Ultrasound in Medicine & Biology Local high-accuracy velocity estimation is important for the ultrasound-based evaluation of regional myocardial function. The ultrasound phase difference at the center frequency of the transmitted signal has been conventionally used for velocity estimation. In the conventional method, spatial averaging is necessary owing to the frequency-dependent attenuation and interference of backscattered waves. Here, we propose a method for suppressing these effects using multifrequency phase differences. The resulting improvement in velocity estimation in the heart wall was validated by in vivo experiments. In the conventional method, the velocity waveform exhibits spike-like changes. The velocity waveform estimated using the proposed method did not exhibit such changes. Because the proposed method estimates myocardium velocity without spatial averaging, it can be used for measuring heart wall dynamics involving thickness changes.

© 2021, The Japan Society of Ultrasonics in Medicine. Purpose: Red blood cell (RBC) aggregation is one of the main factors that determines blood viscosity and an important indicator for evaluating blood properties. As a noninvasive and quantitative method for diagnosing blood properties, our research group estimated the size of RBC aggregates by fitting the scattered power spectrum from the blood vessel lumen with the theoretical scattering characteristics to evaluate the degree of RBC aggregation. However, it was assumed that the propagation attenuation of ultrasound in the vascular lumen was the same regardless of whether RBCs were aggregated or not, which caused systematic errors in the estimated size. Methods: To improve the size estimation accuracy, we calculated and corrected the attenuation of the blood vessel lumen during RBC aggregation and non-aggregation. The attenuation in the blood vessel lumen was calculated with the spectra acquired from two different depths. Results: In the basic experiments using microparticles, the estimation accuracy decreased as the concentration increased in the case of the conventional method, but the estimated size tended to approach the true size irrespective of the concentration, removing the propagation attenuation component with the proposed method. In the in vivo experiment on the human hand dorsal vein, the size was estimated to be larger during RBC aggregation and smaller during non-aggregation using the proposed method. Conclusion: These results suggest that the proposed method can provide precise size estimation by considering the propagation attenuation component regardless of differences in blood conditions such as RBC concentration and degree of aggregation.

© 2020 IEEE. We have developed a non-invasive and quantitative method to estimate the size of RBC aggregates by analyzing ultrasonic backscattering properties from blood vessel lumen and comparing those with the theoretical scattering characteristics. In the present study, we aimed to improve accuracy by calculating and correcting the attenuation in the blood vessel lumen. The attenuation in the blood vessel lumen was calculated with the spectra acquired from two different depths. In the basic experiments using microparticles, the estimated size tended to approach the true size irrespective of the concentration removing the propagation attenuation component by the proposed method.

© 2020 IEEE. To establish an evaluation index for vascular endothelial function, we estimated the change of viscoelasticity of the radial artery during flow-mediated dilatation (FMD) using a developed ultrasonic probe that can simultaneously measure the blood pressure and the diameter at the same position. The elasticity after the recirculation from avascularization was larger than that at rest. Moreover, the elasticity increased 100 seconds after the recirculation. The absolute value of the elasticity was different from that before the avascularization. However, the tendency of the change was consistent with our previous study. These results show the possibility to measure the change of viscoelastic characteristics during FMD using a single ultrasonic probe.

© 2020 IEEE. Measurement of roughness in tens of microns on the luminal surface of the arterial wall is expected to provide the basis for an extremely early diagnosis of atherosclerosis. We have previously proposed a method for measuring the surface profile with micron-order precision by exploiting the longitudinal displacement due to pulsation and measuring the radial displacement due to surface roughness. This method allows estimation of the surface profile without influence by the region of heterogeneous sound velocity between the carotid artery and the skin. However, since the radial displacement of the carotid artery wall measured by ultrasound is not only due to the surface roughness but also the artery expansion due to pulsation, the latter has to be removed. In the present study, a novel method for locally removing radial displacements due to pulsation is proposed by using the spatial distribution of the pulsation component. The proposed method was verified by using a target consisting of urethane resin with a 10-µm-high sawtooth shape on the surface. The agreement with the actual profile was significantly improved by the proposed method. This result indicates that locally removing the pulsation component by the proposed method is useful for accurately estimating the micron-order surface profile of the arterial wall.

硬膜外麻酔において、麻酔針の穿刺位置を確実に特定するために、超音波による胸椎表面の鮮鋭な描出が求められている。そのために、骨の描出と筋組織の描出を区別する必要がある。本報告では、基礎実験により、骨のように超音波を反射する対象物と、筋組織のように超音波を散乱する対象物に対する、反射特性と散乱特性の違いを検討した。また、それらの違いを活かして骨と筋組織の描出を分離する方法を提案し、実験結果に適用した。その結果、反射体の存在と傾きは概ね正しく推定できた。散乱体では、送信ビームの真下に散乱体がある場合で正しく推定できたが、誤推定された箇所があった。今後、散乱体を正しく推定する方法を検討していく。(著者抄録)

© 2020 The Japan Society of Applied Physics. To establish an evaluation index for vascular endothelial function, we developed an ultrasonic probe that can measure changes in blood pressure and blood vessel diameter at the same position in the radial artery. Based on phantom experiments, the pressure waveforms measured using the piezoelectric effect of the ultrasonic probe element and those using a pressure sensor exhibited a high correlation (correlation coefficient: r = 0.979 - 0.999). We confirmed the continuous measurement of the relationship between changes in blood pressure and the diameter from the in vivo experiments. We could then estimate the changes in viscoelasticity by calibrating the output from the probe element to the absolute blood pressure values in advance. The average coefficients of variations were 0.02 and 0.24 for elasticity and viscosity, respectively. This study demonstrated the possibility of measuring changes in the viscoelastic moduli of the radial arterial wall due to flow-mediated dilation using the developed ultrasonic probe.

© 2020 The Japan Society of Applied Physics. An estimation of anisotropic viscoelasticity is important for evaluating muscle lesions. In the previous study, we proposed a method for estimating viscoelasticity in a local region by exciting a phantom specimen from both directions. In the present study, we observed the acoustic field having the locality and directivity generated by dual ultrasound excitation. In addition, the displacement distributions for the isotropic and anisotropic viscoelastic phantoms were measured, and the local generation of large displacement and its directionality was confirmed around the excitation focal point. Furthermore, we applied our viscoelasticity estimation method to the anisotropic viscoelastic phantom. The estimated shear modulus differed depending on the angle between the opposite direction of the ultrasound transducer projected on the phantom surface and longitudinal direction of the cylindrical urethane rubber bundle in the anisotropic viscoelastic phantom. Therefore, the viscoelasticity estimation method in the present study could estimate anisotropic viscoelasticity locally.

© 2020, The Japan Society of Ultrasonics in Medicine. Purpose: The generalized coherence factor (GCF), an adaptive beamforming technique, can reduce unnecessary signals from an unfocused position without reducing the contrast-to-noise ratio. However, the computational complexity of this method is large compared to the conventional delay-and-sum (DAS) beamformer. In the present paper, we propose a novel method to achieve the same reduction effect of unnecessary signals with a smaller computational load than that of the conventional GCF approach. Methods: One of the factors increasing the computational complexity of the GCF-based beamformer compared with DAS is the generation of analytic signals at receiving elements. We clarified the mechanism of generating unnecessary signal components to enable the calculation of the GCF value directly from real signals without generating analytic signals. Furthermore, we proposed a method to filter out these components without generating analytic signals. Results: The GCF values obtained using the proposed and conventional methods were compared and verified using the actual data acquired from a phantom with an ultrasound diagnostic system. We also compared the B-mode images. As a result, equivalent GCF values and similar B-mode image quality were achieved with the proposed method with reduced computational complexity. Conclusion: With the proposed method, generation of analytic signals at receiving elements can be omitted, and as a result, the computational load of the GCF method can be greatly reduced, while preserving the effect of reducing unnecessary signals like with the conventional method.

© 2020 Polish Academy of Sciences. All rights reserved. Plate shaped Fe–Al alloy crystals were successfully grown using the µ-PD method. The orientation and grain size could be controlled by using the well oriented Fe0.95Al0.05 seed crystal. The as-grown Fe0.82Al0.18 and Fe0.80Al0.20 showed the magnetostriction 3/2λ = 121 and 149 ppm, respectively, which is comparable to the values for single crystal samples grown by the Bridgman-Stockbarger method. Distributions of Fe and Al were homogenous along the growth direction within standard deviations of 0.35% and 1.3%, respectively. A prototype vibration energy harvester was demonstrated using the grown Fe–Al alloys.

PURPOSE: Medical ultrasound is often used to specify the puncture position during epidural anesthesia. However, visualization of the thoracic spine is difficult because of the complex structure, i.e., it is difficult to determine whether the thoracic spine or muscle is depicted. Therefore, this study aims to distinguish bone from muscle tissue using the differences in reflection and scattering characteristics of ultrasound. METHODS: We experimentally investigated the difference in signals received from bone and muscle. We proposed a new parameter utilizing the ratio of the amplitude of the received signals averaged in a wide range around the ideal delay line and that only along the ideal delay line, to emphasize the bone. RESULTS: First, we confirmed the difference in signals received from bone and muscle tissue by basic experiments. We also investigated the difference by in vitro experiments using chicken thigh and in vivo experiments in humans. In both experiments, the proposed method succeeded to clearly depict bone, suppressing the depiction of muscle, compared with conventional B-mode imaging. CONCLUSION: Using the difference in the characteristics of reflection from bone and scattering from muscle tissue, we could distinguish bone from muscle tissue with the proposed method.

Measuring myocardial contractile movement caused by electrical excitation leads to early detection of abnormalities of cardiomyocytes due to disease. However, the detailed mechanism of the transition process in the myocardium from dilation to contraction at the pre-ejection period is still unclear. In the present study, we acquired ultrasonic RF signals with a high frame rate of 1.16 ms using the parallel beamforming [1] by transmitting a plane wave with a sector probe. Velocity waveform in the 2D direction, the beam direction (the radial direction in the heart wall), and the direction orthogonal to the beam (the longitudinal direction in the heart) were simultaneously estimated by applying the speckle tracking along the heart wall. The cross-correlation coefficient was interpolated so that the spatial resolutions in displacement estimation along the radial and longitudinal directions were increased to 1.0 and 2.2 μm, respectively. We then detected the propagation speeds of contraction response due to electrical excitation along the radial and longitudinal directions at the pre-ejection period. The radial component of 2D velocity waveforms was measured at 112 points along the septum around the R wave of ECG. The velocity component to RV (LV expansion) and that of LV (contraction) were obtained. In the period around R wave, two components propagated along the septum from the basal to apical sides with speeds of 3 m/s and 6 m/s. On the other hand, for the longitudinal component, three components propagated with speeds of 1 m/s, 3 m/s and 12 m/s. Though these all velocity components were simultaneously measured for the same points in the septum, the situations of 2D velocity waveforms were quite different, which would be useful for understanding what occurs at the pre-ejection period.

For early diagnosis of arteriosclerosis, we have developed methods of measuring arterial wall characteristics such as local elastic modulus and luminal surface roughness by measuring the arterial wall movement. Since the carotid artery moves not only in the radial direction but also in the longitudinal direction due to the contraction of the heart, the movement in the longitudinal direction has to be estimated and introduced into measurement methods of arterial wall characteristics. However, the estimation of the longitudinal movement of the intima-media complex (IMC) is difficult because the acoustic property of IMC is homogeneous in the longitudinal direction, especially in the very early-stage of arteriosclerosis. Therefore, the objective of the present study is to examine an accurate estimation method of the arterial wall movement in the longitudinal direction. The longitudinal displacement of IMC was measured by the block matching method. As the conventional method, the block matching method was applied to the envelope of radio-frequency (RF) signals in IMC. In the present paper, it was also applied to the difference signals of the envelope of RF signals between the neighboring beams to amplify the change of subjects in the longitudinal direction. The block matching methods were applied to the signals in IMC acquired in the right common carotid artery of healthy subjects in the twenties, and the estimated results were compared with the trajectory of the longitudinal movement of IMC which was the change of maximum amplitudes of echo envelope in IMC. In the conventional method, several estimated displacements did not correspond with the trajectory of the longitudinal movement of IMC. By subtracting echo envelope signals in the longitudinal direction, the change of signals was amplified; therefore, the estimated displacements well corresponded with the trajectory of the longitudinal movement of IMC.

High blood glucose level (BGL) is related to the high viscosity of blood. Red blood cells (RBCs) tend to gather each other in the condition of high viscosity. Backscattered echoes become high as RBCs aggregate. Therefore, the intensity of backscattered echo is anticipated to be high as the BGL increases. In the present study, we investigated the relationship between RBC aggregations by ultrasound and the BGL for the development of non-invasive BGL measurement methods. Ultrasonic backscattering echoes for dorsal hand vein and BGLs were repeatedly measured from fasting to 190 min after injecting 40-g glucose for a healthy subject. The brightness of the B-mode image increased as the BGL increased. The brightnesses of B-mode image and the BGLs after 160-190 min were less than those at fasting. The relationship between the brightness of the B-mode image and BGL was almost linear, although the hysteresis characteristic was observed. This is because multiple factors other than BGL are closely related to the RBC aggregations.

© 2019 IEEE. Biomechanics of the cell indicates the inner structure and viability of the cell. Mechanical properties are represented by acoustic properties such as speed of sound (SOS) or acoustic impedance. In the present study, cellular resolution scanning acoustic microscope combined with optical microscope (OptSAM) is developed to observe the change of mechanical properties in cell differentiation. Main part of the OptSAM was consisted of 350 MHz ultrasound transducer mechanically scanned by a piezo-actuator. Thickness, SOS, acoustic impedance, density and elastic bulk modulus of the cell were deduced by the ultrasound responses in both time domain and frequency domain. C2C12 cell changing its form from myoblast to myotube was observed by OptSAM. The value of bulk modulus slightly increased in response to differentiation process. OptSAM non-invasively provides important information on biomechanics of cells without contact or staining.

The propagation of myocardial contraction caused by the conduction of electrical excitation in the heart has been visualized in our previous study. However, it was assumed that the contraction propagated parallel to the heart wall and the propagation speed was constant within the measurement area. In the present study, we estimated the two-dimensional propagation speed of contraction at each local area by ultrasonic measurement, and examined the mechanism of the contraction propagation in the heart by calculating the spatial distribution of the propagation speed vectors. By applying the proposed method to the interventricular septum of the human heart, the propagation speed in the lateral direction was approximately 1.6 times faster than that in the beam direction. The significant difference in propagation speeds between the specialized and ordinary myocardia was detected successfully. This study suggests that the proposed method can detect the myocardial ischemic and arrhythmia regions non-invasively.

It has been revealed that the ultrasound measurement with high temporal resolution is useful for diagnosis of myocardial tissue properties. However, it is considered that the dynamic measurement of the target tissue is affected by the motion of neighbor tissues because of the wide width of the transmitted wave. For this reason, the measurement error is affected by spatial and temporal factors. In the present study, we constructed an experimental system for measuring these effects quantitatively and investigated the accuracy of the velocity measurement using some transmitted waves such as focused, plane, and diverging waves. In the conditions of the present study, the measurement error is minimized at 9° of the angular width of the transmitted wave. This method is useful for evaluating the conditions of transmitted waves for measurements of other targets which need a high temporal resolution such as shear wave, cardiac blood flow, and so on.

An ultrasonic method to measure the changes in radial arterial diameter and blood pressure in a noninvasive manner was proposed to estimate viscoelastic characteristics of the arterial wall to diagnose vascular endothelial dysfunction at an extremely early stage. In the present study, a measurement method of blood pressure using the piezoelectric effect of the ultrasonic probe was investigated. At first, blood pressure waveform measured by the piezoelectric element was discussed using piezoelectric constitutive equations. We confirmed that the blood pressure waveform can be obtained by integrating the waveform measured by the piezoelectric element. Then, a conventional ultrasonic probe was modified to measure a blood pressure waveform and the measurement is demonstrated. Changes in the radial diameter was also measured using an ultrasonic diagnosis equipment with a conventional linear ultrasonic probe. The measured voltage by the piezoelectric element was of the same order as the result estimated from the theoretical consideration with typical material constants of the piezoelectric element. The diameter expanded with an increase in blood pressure and then gradually returned due to the decrease in blood pressure with viscosity. From the relationship between the arterial diameter and blood pressure, the hysteresis characteristic of the artery wall during one heartbeat was confirmed.

Purpose: To develop methods for noninvasively and quantitatively measuring blood glucose levels. Methods: In the present study, we evaluated the degree of red blood cell (RBC) aggregation at a low shear rate robustly by introducing two new parameters determined from changes in the scattering power spectrum of the echoes from the intravascular lumen before and after cessation of blood flow. We also considered the clinical significance of these parameters and the change in sizes estimated by the conventional method by comparing them with the blood glucose level obtained just before the ultrasonic measurements. We performed the measurements in one healthy subject and 11 diabetic patients. Results: A correlation was found between one of the proposed parameters and the blood glucose level. However, the p value was not very high, and one of the reasons for the decline of the correlation will be that some factors other than blood glucose also affect RBC aggregation. Conclusion: The proposed method has potential for clinical application after elucidation of the various factors affecting RBC aggregation.

Purpose: With commercial ultrasonic equipment, the sound velocity is fixed to a constant value of 1530 or 1540 m/s, which is used for beam formation. However, the assumption of a constant sound velocity is not optimal, as the sound velocity in a living body is heterogeneous. In this study, a novel method was proposed to estimate the distribution of the sound velocity in a region of interest. Methods: The sound velocity distribution was estimated by fitting the theoretical propagation time of the ultrasonic wave from the scatterer to each of the probe elements with measured values. Results: In a phantom experiment, the sound velocity distribution was estimated by the proposed method with a maximum estimation error of 0.6%, and the resultant local sound velocity values successfully improved the quality of the ultrasonic image. Conclusion: The proposed method has the potential to improve ultrasonic image quality in in vivo experiments by estimating the sound velocity distribution.

We proposed a robust analysis method for the acoustic properties of biological specimens measured by acoustic microscopy. Reflected pulse signals from the substrate and specimen were converted into frequency domains to obtain sound speed and thickness. To obtain the average acoustic properties of the specimen, parabolic approximation was performed to determine the frequency at which the amplitude of the normalized spectrum became maximum or minimum, considering the sound speed and thickness of the specimens and the operating frequency of the ultrasonic device used. The proposed method was demonstrated for a specimen of malignant melanoma of the skin by using acoustic microscopy attaching a concave transducer with a center frequency of 80 MHz. The variations in sound speed and thickness analyzed by the proposed method were markedly smaller than those analyzed by the method based on an autoregressive model. The proposed method is useful for the analysis of the acoustic properties of bilogical tissues or cells.

In our studies on ultrasonic elasticity assessment, minute change in the thickness of the arterial wall was measured by the phased-tracking method. However, most images in carotid artery examinations contain multiple-reflection noise, making it difficult to evaluate arterial wall elasticity precisely. In the present study, a modified phased-tracking method using the pulse inversion method was examined to reduce the influence of the multiple-reflection noise. Moreover, aliasing in the harmonic components was corrected by the fundamental components. The conventional and proposed methods were applied to a pulsated tube phantom mimicking the arterial wall. For the conventional method, the elasticity was 298 kPa without multiple-reflection noise and 353 kPa with multiple-reflection noise on the posterior wall. That of the proposed method was 302 kPa without multiple-reflection noise and 297 kPa with multiple-reflection noise on the posterior wall. Therefore, the proposed method was very robust against multiple-reflection noise.

We proposed a new method for estimating the viscoelastic property of the local region of a sample. The viscoelastic parameters of the phantoms simulating the biological tissues were quantitatively estimated by analyzing the frequency characteristics of displacement generated by acoustic excitation. The samples were locally strained by irradiating them with the ultrasound simultaneously generated from two point-focusing transducers by applying the sum of two signals with slightly different frequencies of approximately 1 MHz. The surface of a phantom was excited in the frequency range of 20–2,000 Hz, and its displacement was measured. The frequency dependence of the acceleration provided by the acoustic radiation force was also measured. From these results, we determined the frequency characteristics of the transfer function from the stress to the strain and estimated the ratio of the elastic modulus to the viscosity modulus (K/η) by fitting the data to the Maxwell model. Moreover, the elastic modulus K was separately estimated from the measured sound velocity and density of the phantom, and the viscosity modulus η was evaluated by substituting the estimated elastic modulus into the obtained K/η ratio.

Pulse wave velocity (PWV) is used as a diagnostic criterion for arteriosclerosis, a major cause of heart disease and cerebrovascular disease. However, there are several problems with conventional PWV measurement techniques. One is that a pulse wave is assumed to only have an incident component propagating at a constant speed from the heart to the femoral artery, and another is that PWV is only determined from a characteristic time such as the rise time of the blood pressure waveform. In this study, we noninvasively measured the velocity waveform of small vibrations at multiple points on the carotid arterial wall using ultrasound. Local PWV was determined by analyzing the phase component of the velocity waveform by the least squares method. This method allowed measurement of the time change of the PWV at approximately the arrival time of the pulse wave, which discriminates the period when the reflected component is not contaminated.

Scanning acoustic microscopy (SAM) using impulsive signals is useful for characterization of biological tissues and cells. The operating center frequency of an ultrasonic device strongly depends on the performance characteristics of the device if the measurement is conducted by using impulsive signals. In this paper, a method for the design of ultrasonic devices for SAM using impulsive signals was developed. A new plane-wave model was introduced to calculate frequency characteristics of loss of ultrasonic devices by taking into account the conversion loss at the ultrasonic transducer, the transmission loss at the acoustic anti-reflection coating, and the propagation loss in the couplant. Ultrasonic devices were fabricated with a ZnO ultrasonic transducer using two acoustic lenses with aperture radii of 1.0 mm and 0.5 mm, respectively. The frequencies at which measured losses became minima corresponded to the calculation results by the plane-wave model. This numerical calculation method is useful for designing ultrasonic devices for acoustic microscopy using impulsive signals.

© 2017 Elsevier B.V. Melt growth of scintillating halide crystals is reviewed. The vertical Bridgman growth technique is still considered as very popular method that enables production of relatively large and commercially attractive crystals. On the other hand, the micro-pulling-down method is preferable when fabrication of small samples, sufficient for preliminary characterization of their optical and/or scintillation performance, is required. Moreover, bulk crystal growth is also available using the micro-pulling-down furnace. The examples of growths of various halide crystals by industrially friendly melt growth techniques including Czochralski and edge-defined film-fed growth methods are also discussed. Finally, traveling molten zone growth that in some degree corresponds to horizontal zone melting is briefly overviewed.

The temperature dependences of the acoustic properties of Ca3Ta(Ga-1% Al-x(x)) 3Si(2)O(14) [CTGAS(x)] were experimentally studied as a function of the Al substitution content x. Five specimens, i.e., one each of X-, Y-, and Z-, and two rotated Y- cut specimens, were prepared from each crystal ingot of CTGAS(x) (x = 0, 0.25, 0.50, and 0.75) grown by the Czochralski technique. The longitudinal wave and shear wave velocities of CTGAS(x) were measured at three temperatures ranging from 291 to 300 K, then acoustically related physical constants (elastic, piezoelectric, and dielectric constants and coefficient of thermal expansion) were determined at approximately room temperature. The results revealed that the temperature coefficients of all the constants linearly changed with Al content. By one of the calculations using the constants and their temperature coefficients determined in this study, we demonstrated their capability to predict suitable conditions (i.e., cut angle, propagation direction, and chemical composition) for acoustic wave devices although they were determined in a narrow temperature range. (C) 2017 The Japan Society of Applied Physics.

The relationship among lattice constant a, Al content, and acoustic properties were experimentally examined using a plate specimen perpendicular to Y-axis prepared from Ca3Ta(Ga0.75Al0.25) 3Si2O14 [CTGAS(0.25)] single crystal grown by Czochralski method. As the acoustic properties, leaky surface acoustic wave (LSAW) velocities with different propagation directions, X-and Z-propagations, and longitudinal wave velocity propagating along Y-axis direction were measured by the line-focus-beam/plane-wave ultrasonic-material-characterization (LFB/PW-UMC) system. The measured results of LSAW velocity distributions revealed inhomogeneity in radial direction of the crystal ingot exhibiting lower velocity area at the center of the ingot. In addition, the distributions of lattice constant a and chemical composition (especially Al content) were measured along the radial direction. Abnormal changes suggesting existence of residual stresses concentrated on the central part of the crystal ingot other than the effect of chemical composition change were detected from the relationships among the measured parameters.

Platinum (Pt) crystalline fibers were grown from the melt by the micro-pulling-down (mu-PD) method using the ZrO2 ceramics crucible. The diameter of the grown Pt fiber was controlled by the phi 1 mm outlet made at the bottom of the crucible and the Pt fiber of 0.95 +/- 0.03 mm in diameter and over 5 m in length was obtained at 10 mm/min pulling-down rate. In addition, the Pt fiber was grown at 1-110 mm/min pulling rates while the liquid-solid interface reached the bottom of the crucible and the crystal growth became unstable at 120 mm/min pulling rate. Few grain boundaries were observed in the scanning electron microscopy image of the Pt fibers and there were some spots with high intensity in the pole figures.

Ce-doped (Gd, La)(2)Si2O7 scintillators have fast decay time and keep high light output even at high temperature (similar to 150 degrees C). To improve the scintillation properties such as light output and decay time, Ce-doped (Gd, La)(2)Si2O7 scintillators codoped with the divalent ions (e.g. Mg2+, Ca2+) have been studied. In this study, we focused on the other divalent ions (Sr2+ and Ba2+), and investigated their effect on the scintillation properties and temperature dependence of light output. The absorption due to Ce4+ was not observed for Sr or Ba codoping. The light outputs were degraded by Sr2+ or Ba2+ codoping, while the decay times at room temperature were not changed for the samples codoped with divalent ions. On the other hand, the temperature dependence of light output for Ba-codoped sample was improved, and the light output value at 175 degrees C was 36,000 photons/MeV, which was 93% of that at 25 degrees C. (C) 2017 Elsevier B.V. All rights reserved.

We evaluated the elastic properties of the compressive stress (CS) layer of chemically tempered glass by ultrasonic microspectroscopy (UMS) in a very high frequency (VHF) range. Two commercial aluminosilicate glass specimens were prepared, and one of them was chemically tempered. Changes in elastic properties in the CS layer with the residual stress introduced by the exchange of Na+ ions for larger K+ ions were estimated by precisely measuring the densities and longitudinal and shear velocities for both the tempered and nontempered specimens. Using a single-layer model for the surface layer, we observed drastic increases in bulk-wave velocities and significant decreases in attenuation coefficients. We determined that the average elastic properties, namely, the elastic constants c11 and c44, and the density of the surface layer, were 9.6 and 7.1, and 1.2% larger than those of the nontempered specimen, respectively. We also estimated the distributions of the elastic properties according to the complementary error function (CEF) for the distribution of K+ ion concentration. Furthermore, using a line-focus-beam (LFB) system, we measured the frequency characteristics of the velocity (VLSAW) of leaky surface acoustic waves (LSAWs) on a water-loaded surface of the tempered specimen and clarified that the distributions of the elastic properties did not follow the CEF. The LFB system can be used for analyzing/determining details of the surface properties and is a promising tool for evaluating and characterizing chemically tempered glass and tempering process conditions.

CaTa(Ga1-xScx)(3)Si2O14 (CTGSS) single crystals with various Sc concentrations (x = 0, 0.1, 0.2, 0.3, and 0.4) were grown by the micro-pulling-down method and their structure and chemical composition were evaluated. Through the powder X-ray diffraction (XRD) measurement and backscattered electron (BSE) imaging, it was demonstrated that all the CTGSS crystals with different Sc concentration were successfully grown as langasitetype structure although some secondary phases were observed for the crystals with x = 0.2, 0.3 and 0.4. Lattice parameters calculated from the powder XRD pattern generally increased with Sc substitution. Measured parameters for CTGSS crystal with x = 0.1 were larger permittivity epsilon(T)(11)/epsilon(0) and lower electromechanical coupling coefficient k(12) and piezoelectric constant d(11) than those for CTGS crystal with x = 0. It was also suggested that piezoelectric constant |d(14)| became larger due to the Sc substitution.

We performed depth analysis of a compression layer in Corning Gorilla Glass 3, one of commercialized chemically-strengthened glasses, using depth-resolved micro-Raman spectroscopy. We obtained a depth variation of Raman spectra and an ion-exchange rate of Na for K was determined by energy dispersive X-ray spectroscopy. We found that a peak position around 1100 cm(-1) in the Raman spectra is shifted to higher wavenumber and the ion-exchange rate of Na for K increases with a decreasing depth when shallower than similar to 30 mu m. This correlation can be qualitatively explained as follows: compression of a TO2 tetrahedra network (T = Si or Al) induced by the ion exchange gives rise to an increase in frequency of vibrational modes of the TO4 tetrahedra. (C) 2016 The Ceramic Society of Japan. All rights reserved.

The acoustic properties of Ca3Ta(Ga1-xAlx)(3)Si2O14 (CTGASx) were experimentally studied as a function of the Al substitution content x in the ranges from x = 0 to 0.50. Five specimens, X-, Y-, Z-, 35 degrees Y-, and 140 degrees Y- cut, were prepared from each crystal of CTGASx (x = 0, 0.25, and 0.50) grown by the Czochralski technique. Longitudinal wave and shear wave velocities for CTGASx linearly increase with Al content for all propagation directions. Dielectric constants and density were measured and then elastic and piezoelectric constants were determined from the measured velocities for each crystal. The results revealed that all of the constants change linearly with Al content. From the relationship, the constants for CTAS (x = 1) were estimated. Calculations of the velocities using the determined constants also suggested that the maximum electromechanical coupling factor k(2) for the slow shear wave mode propagating along the rotated Y- axis direction of CTAS was improved to 4.42% compared with 3.83% for CTGS, owing to the Al substitution effect. (C) 2016 The Japan Society of Applied Physics

We developed a procedure for fabricating a Fabry-Perot optical cavity with less long-term length variation. We fabricated a homogenized TiO2-SiO2 ultralow-expansion (ULE) glass ingot from a commercial TiO2-SiO2 ULE glass ingot with striae. We also controlled the zero-crossing temperature of the coefficient of thermal expansion of the homogenized ingot to approximately 30 degrees C by heat treatment at 970 degrees C for 72 h to change the fictive temperature of the ingot. A 100-mm-long cavity spacer was carefully fabricated while reducing the mechanical residual stress introduced by machining. A cavity composed of the spacer and two mirrors of 39-layered Ta2O5/SiO2 films exhibited a high finesse of 420,000 at 729 nm and a high length stability of 13 fm/day after 500 days from the beginning of the measurement at a constant temperature of 29.78 degrees C. (C) 2015 The Japan Society of Applied Physics

Biomechanics of the cell has been gathering much attention because it affects the pathological status in atherosclerosis and cancer. In the present study, an ultrasound microscope system combined with optical microscope for characterization of a single cell with multiple ultrasound parameters was developed. The central frequency of the transducer was 375 MHz and the scan area was 80 x 80 mu m with up to 200 x 200 sampling points. An inverted optical microscope was incorporated in the design of the system, allowing for simultaneous optical observations of cultured cells. Two-dimensional mapping of multiple ultrasound parameters, such as sound speed, attenuation, and acoustic impedance, as well as the thickness, density, and bulk modulus of specimen/cell under investigation, etc., was realized by the system. Sound speed and thickness of a 3T3-L1 fibroblast cell were successfully obtained by the system. The ultrasound microscope system combined with optical microscope further enhances our understanding of cellular biomechanics.

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

Scanning acoustic microscope (SAM) is useful for tissue characterization because it is possible to obtain two-dimensional information of acoustic properties, viz., velocity and attenuation coefficient, in the microscopic region. We have studied development of SAM and its application to quantitative evaluation of biological tissue and a single cell. We developed a SAM system using a pulse signal and analytical procedure to obtain acoustic properties. Recently, we also developed an acoustic and optic hybrid system to obtain both optical and elastic images and acoustic properties for a single cell in real time. We applied the system to a 3T3-L1 mouse fibroblast cell using an acoustic lens with center frequency of 250 MHz. Measurements were conducted immediately and enough later after takeoff from the culture apparatus. Sound velocities were 1602 m/s and 1558 m/s, and thicknesses were 7.9 μm and 16 μm, respectively. Properties changes of the cell were successfully detected quantitatively.

Recently, the biomechanics of cell has received attention because the study on the biomechanics will lead to development of diagnosis and treatment of cancer and arteriosclerosis. Most methods on the measurement of biomechanics require direct contact to the cell. Because the square of sound speed is proportional to the cell elasticity, non-contact measurement of sound speed with ultrasound microscopy can obtain the mechanical properties. In the present study, quantitative measurement of cell parameters such as thickness, sound speed, acoustic impedance, density, bulk modulus, attenuation and images of each parameter are successfully obtained. The transducer had 150 MHz center frequency and f-number of 0.88 and focal length of 3.8 mm. Pulse spectrum analysis was applied to calculate thickness and sound speed of the cells because the signal from a cell surface was not distinguished from the echo from the petri dish. This study may contribute measurement of cellular biomechanics.

Precise measurement of blood flow is important because blood flow closely correlates formation of thrombus and atherosclerotic plaque. Among clinically applied modalities for blood flow measurement, color Doppler ultrasound shows two-dimensional (2D) distribution of one-dimensional blood flow component along the ultrasound beam. In the present study, 2D blood flow vector is obtained with high temporal and bidirectional Doppler ultrasound technique. Linear array probe with the central frequency of 7.5 MHz and an ultrasound data acquisition system with 128 transmit and 128 receive channels were equipped. Frame rate of 5 kHz was achieved by parallel receive beam forming with a wide transmitted wave. The flow velocity was measured from two different angles by beam steering. The interval of two measurements was 0.8 msec and it was considered as almost one moment to obtain 2D blood flow vector. B-mode image and 2D blood flow vector of the pulsatile flow in a carotid artery model showed small vortex at the bifurcation area. The method was also applied for visualization of in vivo blood flow vector in human carotid arteries. 2D blood flow measurement may predict the risk area of thrombus and plaque formation induced by abnormal blood flow.

We discussed a method of evaluating surface compressive layer of tempered glasses by the ultrasonic microspectroscopy (UMS) technology. Chemically tempered glass specimens and the non-tempered specimen were prepared. Velocities of leaky surface acoustic wave (LSAW) and leaky surface skimming compressional wave (LSSCW) were measured by the line-focus-beam ultrasonic material characterization system. LSAW and LSSCW Velocities increased drastically caused by the surface compressive stress. Velocity differences caused by the difference of chemical strengthening process conditions were successfully detected. Resolution to depth of compressive stress layer by the LSAW velocity measurement was +/- 0.11 mu m. Frequency characteristics of LSAW velocity have possibility of evaluating elastic properties distributions in the depth direction of tempered layer. Velocities changes were mainly caused by elastic constants changes by the bulk acoustic properties measurements.

Biomechanics of the cell has been gathering much attention because it affects the pathological status in atherosclerosis and cancer. In the present study, an ultrasound and optical combined microscope system for characterization of a single cell with multiple ultrasound parameters was developed. The central frequency of the transducer was 375 MHz and the scan area was 80 x 80 micron with up to 200 x 200 sampling points. An inversed optical microscope was installed in the system and simultaneous observation of the cells cultured in the petridish was available. Two-dimensional mapping of the multiple ultrasound parameters such as attenuation, sound speed and acoustic impedance as well as the thickness and density of the cell was realized by the system. Sound speed and thickness of 3T3-L1 fibroblast cell were successfully obtained by the system. The ultrasound and optical combined microscope system may contribute to understand the cellular biomechanics.

TiO2-SiO2 glass is one of the leading candidates for optical elements of extreme ultraviolet lithography. TiO2-SiO2 glass synthesized by the soot method has shown striae related to inhomogeneity of TiO2 concentration formed in the planes perpendicular to soot growth direction in the synthesis process. It can induce CTE variation and localized surface roughness. Striae were characterized in three modes by polarization microscope. Such striae were improved with an improved gas condition and developing a modified material gas supply system. Specimen prepared from the improved TiO2-SiO2 glass was evaluated by a line-focus-beam ultrasonic material characterization system, using a surface-acoustic-wave mode. Improved glass had 43% striae level compared to conventional glass by birefringence measurement, 31% compared to conventional glass by the ultrasonic measurement. It was found that improved glass had good homogeneity to both directions perpendicular and parallel to striae plane.

The dielectric, elastic, and piezoelectric constants of langasite family single-crystal La3Ta0.5Ga5.3Al0.2O14 (LTGA) were measured by combing plane-wave ultrasonic microspectroscopy (PW-UMS) technology with the resonance-antiresonance method in a range from room temperature to 1000 degrees C. The influence of dielectric loss at high temperatures on resonance and antiresonance frequencies was discussed. At room temperature, the piezoelectric constants d(11) and d(14) were 6.62 and -4.65 pC/N, respectively. d(11) increased to 7.5 pC/N at 1000 degrees C. The electromechanical coupling factor k(12) was about 16.8% in the entire temperature range. All the necessary parameters of the LTGA crystal for acoustic wave applications at high temperatures were determined in this research. (C) 2012 The Japan Society of Applied Physics

The fundamental acoustic properties of amorphous Ta2O5 and Nb2O5 thin films prepared by RF sputtering were evaluated using a Rayleigh-type surface acoustic wave (SAW) on 128 degrees YX-LiNbO3 and a shear-horizontal-type SAW on 36 degrees YX-LiTaO3. The elastic constants c(11) and c(44) of the thin films were determined from the measured phase velocities of two SAW modes with mutually perpendicular particle motion. Although the elastic constants of the Ta2O5 thin film were found to be approximately 14-17% larger than those of the Nb2O5 thin film, it was clarified that the Ta2O5 thin film has a stronger SAW trapping effect than the Nb2O5 thin film because the density of the former was measured to be 1.5 times higher than that of the latter. On the other hand, the Nb2O5 thin film has a smaller propagation loss for a Rayleigh-type SAW, a lower temperature coefficient of delay, and a higher refractive index than the Ta2O5 thin film. (C) 2012 The Japan Society of Applied Physics

A determination method of accurate acoustical physical constants and their temperature coefficients was demonstrated for La3Ta0.5Ga5.3Al0.2O14 (LTGA) single crystal using the ultrasonic microspectroscopy (UMS) technology combined with the resonance method. Several specimens (X-, Y-, Z-, 29.14 degrees Y-, and 150.86 degrees Y-cut) were prepared from an LTGA ingot. Acoustical physical constants and their temperature coefficients around room temperatures were determined using the longitudinal-and shear-wave velocities measured by the UMS system, dielectric constants, density, and thermal expansion coefficients. Measured leaky surface acoustic wave (LSA W) velocities and calculated ones using the determined constants at 23 degrees C were compared, resulting in good agreement within -3.0 to 1.1 m/s for all propagation directions. Using four X-cut rotated Y-bar (-30 degrees y, 0 degrees y, 15 degrees Y, 30 degrees Y) specimens and Y-cut specimen prepared from the same ingot, the temperature coefficients in a range from -30 to 80 degrees C were also obtained by the resonance method. Combining the temperature coefficients obtained by the resonance method with the accurate constants obtained by the UMS technology, we can determine more reliable constants and temperature coefficients.

Experimental procedures to evaluate the fictive temperature (T(F)) of synthetic silica glass were developed using ultrasonic microspectroscopy (UMS) technology by measuring longitudinal-wave velocity (V(l)). Two kinds of commercial synthetic silica glass (without and with water) were demonstrated, resulting in the establishment of calibration lines between V(l) and T(F) with a resolution within 1 degrees C and clear observation of their hydroxyl (OH) dependences. This ultrasonic method and system will be extremely useful and effective for improving mass-production conditions of glass ingots as well as for conducting basic studies on glass science. (C) 2011 The Japan Society of Applied Physics

This paper presents the development of a practical system for super-precise evaluation of zero-CTE temperatures T(zero-CTE) of TiO(2)-SiO(2) glasses for extreme ultraviolet lithography (EUVL) by measuring leaky surface-acoustic-wave (LSAW) velocity V(LSAW) with a line-focus-beam ultrasonic material characterization (LFB-UMC) system. This new system can evaluate T(zero-CTE) from 20 to 150 degrees C on the surfaces of glass substrates for photomasks and optical mirrors located at different positions in EUVL systems. This system operates in a stabilized temperature measurement environment (e.g., 23.00 degrees C). It was demonstrated at 225 MHz for homogenized TiO(2)-SiO(2) glass specimens with different annealing temperatures and realized an extremely homogeneous glass ingot with Delta T(zero-CTE) of 1.6 degrees C around 23.2 degrees C. This ultrasonic system enables both glass manufacturers and users to speedily inspect all glass substrates with reliable data of T(zero-CTE).

A new set of acoustical physical constants for ZnO was obtained by ultrasonic microspectroscopy (UMS) using very conductive and resistive (001), (100), and (101) ZnO specimens, grown by the hydrothermal method. The specimens were selected from a lot of small ZnO crystals evaluated with the velocity of leaky surface acoustic waves (LSAWs) on a water-loaded specimen surface, in order to identify proper specimens or proper measurement positions for bulk-wave velocity measurements. The constants were determined with measured bulk-wave velocities, according to the determination procedures developed previously. Their accuracies were estimated by comparing the measured LSAW velocities with the calculated ones using the determined constants, within 3.1 m/s. We observed LSAW velocity distributions and bulk-wave velocity dispersions for some specimens that were related to the resistivity distributions on the specimen surfaces and inside the specimens. We established experiment procedures to apply our UMS technology to ZnO crystals in this study. This ultrasonic method is useful for further understanding ZnO crystal growth processes in the hydrothermal method. This application is extended to other class-6mm crystals. (C) 2010 The Japan Society of Applied Physics

A micro line-focus-beam (LFB) ultrasonic device was developed to improve the spatial resolution of the LFB ultrasonic material characterization (UMC) system. This device was demonstrated at 225 MHz with a wedge-shaped, slightly focused ultrasonic beam from a ZnO-film transducer fabricated on a large cylindro-convex surface with a 13-mm radius, not on the flat surface in a normal LFB ultrasonic device, and achieved over three-times improvement. We confirmed its ability to detect crystal anisotropy and to evaluate elastic inhomogeneity with steep variations using ZnO specimens. This device expands the potential of the LFB-UMC system for materials analyses. (C) 2009 The Japan Society of Applied Physics

We theoretically and numerically investigated procedures for accurately determining the acoustical physical constants of piezoelectric hexagonal (class 6mm) crystals, taking ZnO as an example, using bulk-wave velocities and leaky surface acoustic wave (LSAW) velocities acquired by ultrasonic microspectroscopy technology. Selection of appropriate propagation modes and directions for eight velocity measurements to facilitate accurately determining five elastic constants (c(11)(E), c(12)(E), c(13)(E), c(33)(E), and c(44)(E)) and three piezoelectric constants (e(15), e(31), and e(33)) was discussed in addition to measurements of two dielectric constants (epsilon(S)(11) and epsilon(S)(33)) and the density (rho). Several determination procedures were obtained. Using only bulk-wave velocities measured for Y-cut, Z-cut, and several rotated Y-cut crystalline plane specimens provided the best determination accuracies for constants c(13)(E), c(33)(E), e(31), and e(33). Favorable determination accuracies were also achieved using several sets of two rotated Y-cut crystalline plane specimens such as (101) and (102). Conductive specimens of (001) and (102) with a resistive (103) specimen made the bulk-wave measurements simpler, resulting in greatly improved determination accuracies. The additional use of LSAW velocity with one conductive (001) specimen enabled the determination procedures to be simplified, resulting in acceptable accuracy for c(13)(E). Measurements of bulk-wave velocities and LSAW velocities for just two resistive Y-cut and Z-cut specimens could determine all the constants, albeit with some deterioration in accuracy, especially for e(31) and e(33). This will be useful for preliminary determination of the constants for precious crystals. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3141784]

Preliminary experiments and numerical calculations were conducted for developing a new ultrasonic method of evaluating resistivity distributions in ZnO single crystals using the line-focus-beam ultrasonic material-characterization system. Velocity and attenuation of leaky surface acoustic waves (LSAWs) were measured at 225 MHz on three Z-cut ZnO specimens with different resistivities. We observed drastic LSAW velocity and attenuation changes associated with relaxation between piezoelectricity and semiconduction for LSAW propagation: 56 m/s in velocity and 0.012 in normalized attenuation around a resistivity of 8.3 Omega m. This ultrasonic method is promising for ZnO crystal characterization. (C) 2009 The Japan Society of Applied Physics

This paper presents a calibration line between leaky surface acoustic wave (LSAW) velocities (V(LSAW)) and coefficient-of-thermal-expansion (CTE) characteristics for TiO(2)-doped SiO(2) (TiO(2)-SiO(2)) glass to evaluate the absolute CTE by the line-focus-beam ultrasonic material characterization (LFB-UMC) system. Commercial TiO(2)-SiO(2) ultra-low-expansion glass and synthetic silica glass were selected as specimens. We measured V(LSAW) by the LFB-UMC system and CTE characteristics by dilatometers, and obtained relationships among V(LSAW), CTE at 22 degrees C {CTE(22 degrees C)} and zero-CTE temperature {T(zero-CTE)}. Resolutions of CTE(22 C) and T(zero-CTE) determined by the LSAW velocity measurement were estimated as +/-0.72 (ppb/K) and +/-0.14 degrees C (+/-2 sigma, sigma: standard deviation) at 225 Hz. Both manufacturers and users can precisely inspect T(zero-CTE) for all EUVL-grade ultra-low-expansion glass substrates by this indirect evaluation method using the calibration line.

We evaluated eleven ZnO polycrystalline films with different thicknesses fabricated on silica glass substrates by DC sputtering and RF sputtering methods using a line-focus-beam ultrasonic material characterization (LFB-UMC) system. We measured fH (product of frequency f and film thickness H) dependences of leaky surface acoustic wave (LSAW) velocities for each ZnO-film specimen. The calculated LSAW velocities decreased from 3424.3 m/s for silica glass to 2671.6 m/s for Z-cut ZnO single crystal as fH increased. The measured LSAW velocities became lower than the calculated ones: decreases of 42 m/s for the DC-ZnO film and 27 m/s for the RF-ZnO film from a calculated value of 2672.1 m/s at fH = 1680 Hz·m. These velocity decreases were related to the FWHM in c-axis orientation, resulting in decreases in elastic constant c44 E associated with ZnO polycrystalline film structure: about 6% for the DC-ZnO film and about 3% for the RF-ZnO film. We also demonstrated the capability of the system for evaluating film thickness distributions through LSAW velocity distributions. This ultrasonic method is useful for characterization of polycrystalline and epitaxial films. ©2009 IEEE.

In this paper, we tried to evaluate several small ZnO single crystals grown by the hydrothermal method using a micro-line-focus-beam ultrasonic material characterization (LFB-UMC) system. We measured leaky surface-acoustic-wave (LSAW) velocity distributions at 225 MHz for the top and bottom surfaces of three (100) (Y-cut) ZnO specimens with different colors, i.e. different electrical properties. We prepared a standard specimen of YX-ZnO, proper for calibrating the LFB system, which is independent of the piezoelectricity of ZnO. We evaluated the Y-cut specimen surfaces using the piezo-active Z-axis LSAW propagation, resulting in a high velocity of 2649 m/s for a very resistive (&gt 100 Ωm) surface and a very low velocity of 2618 m/s for a very conductive (&lt 1 Ωm) surface. Additional experiments for cross-sectional ±c-plane surfaces of one Y-cut ZnO specimen plate revealed significant LSAW velocity distributions associated with the crystal growth condition changes. This ultrasonic method will be useful for further understanding the crystal growth processes. ©2009 IEEE.

Ultrasonic microspectroscopy technology was applied to characterization of synthetic silica glasses. Acoustic properties (longitudinal and shear velocities, leaky surface acoustic wave velocity, and density), fictive temperature Tf, chlorine concentration C(Cl), and OH concentration C(OH) were measured, and related relationships among their properties were discussed. The longitudinal velocities in the acoustic properties have the highest sensitivities of 5.93°C/(m/s), -202 wtppm/(m/s), and -31 wtppm/(m/s), with resolutions of 0.6°C, 20 wtppm, and 3.1 wtppm, to T f, C(Cl), and C(OH), respectively. The variations in the acoustic velocities due to Tf, C(Cl), and C(OH) are mainly caused by variations in elastic constants, except for shear velocity due to C(OH). ©2009 IEEE.

A TiO2-SiO2 glass ingot was fabricated by the soot method and homogenized by the zone-melting method. Elastic homogeneities of specimens prepared at different production stages were evaluated by measuring leaky surface acoustic wave (LSAW) velocity V-LSAW using the line-focus-beam ultrasonic material-characterization system at 225 MHz. The homogeneous V-LSAW distribution was within +/- 1.13 m/s, corresponding to a variation of the coefficient of thermal expansion (CTE) of +/- 5 ppb/K, and no striae were observed. V-LSAW changes associated with residual stress inside the ingot could be detected. The relationships among V-LSAW, TiO2 concentration, density, CTE characteristics, and fictive temperature were investigated. We found the possibility for extremely homogeneous TiO2-SiO2 glass with zero-crossing in CTE at a desired room temperature. (C) 2008 The Japan Society of Applied Physics.

Basic acoustic properties of AlN single crystal Y-cut and Z-cut plates, grown by the physical vapor transport method, were evaluated using ultrasonic microspectroscopy (UMS) technology. A method of determining the acoustical physical constants with two specimens was developed by measuring the velocities of longitudinal and shear waves and leaky surface acoustic waves (LSAWs). We obtained accurate bulk-wave velocities, LSAW velocities and their distributions in the specimen surfaces, and the density with great differences compared with the calculated ones using the reported constants. We also determined the corresponding constants. This UMS technology will contribute to the further development of AlN crystals. (C) 2008 The Japan Society of Applied Physics.

Accurate measurements of the longitudinal and shear velocities, densities, elastic constants, and lattice constants of two sapphire single-crystal ingots grown by the Bagdasarov method and the Kyropulos method are reported. No significant differences were observed in the acoustic properties of the two crystals. The elastic constants and densities were accurately determined, with considerable differences in c(13), c(14), and c(33), as compared with the published constants, and the sign Of c(14) was confirmed to be positive.

In this paper, we tried to fabricate a TiO2-doped SiO2 (TiO2-SiO2) glass ingot by the soot method, and homogenized the glass ingot by the zone-melting method. Homogeneities of the specimens were evaluated by measuring leaky surface acoustic wave (LSAW) velocity using the line-focus-beam ultrasonic material characterization system at 225 MHz. Two-dimensional LSAW velocity distributions having an average velocity of 3304.08 m/s with a maximum velocity difference of 3.85 m/s were measured for a homogenized specimen. Striae were not observed for the specimen. The velocity difference corresponds to 17.0 ppb/K from the sensitivity of the LSAW velocity to the CTE {4.41 (ppb/K)/(m/s)l. However, the velocity distributions excluding the edge parts were within +/- 1.13 m/s, corresponding to the CTE specification of +/- 5 ppb/K required for EUVL-grade glass. We also discussed the relationship between LSAW velocities and fictive temperatures by heat-treating a part of the homogenized specimen.

This paper describes an investigation of determining acoustical physical constants of ZnO. We obtained three specimens of (001)-, (100)-, and (101)-ZnO crystal substrates prepared from three very small single crystals, grown by the hydrothermal synthesis method. We measured bulk-wave velocities in the frequency range from 50 MHz to 300 MHz and LSAW velocities at 225 MHz using the ultrasonic microspectroscopy (UMS) technology. We observed that the specimens included partially conductive region inside the crystals. We determined the constants more accurately except for e(15) and e(31).

We experimentally and theoretically studied an exact measurement model for attenuation of leaky surface acoustic waves (LSAWs) using the line-focus-beam ultrasonic-material-characterization (LFB-UMC) system. We measured the I-SAW propagation characteristics (viz., phase velocity and attenuation) for two specimens of synthetic silica (SiO2) glass and borosilicate (Pyrex) glass at 225 MHz. We detected acoustic loss of LSAWs due to the acoustic absorption effect for the Pyrex glass by calibrating the measurement results with reference to those of the SiO2 glass.

We proposed a new coefficient-of-thermal-expansion (CTE) evaluation method for ultra-low expansion glasses using the line-focus-beam ultrasonic material characterization system. In this paper, we investigated evaluation procedures for photomasks and optical mirrors with practical size used as reflective optics in extreme ultraviolet lithography (EUVL) systems. Two specimens were prepared with their surfaces parallel to the striae plane from commercial TiO2-SiO2 ultra-low-expansion glass ingots. Homogeneities/inhomogeneities of specimens were evaluated at 225 MHz. Evaluation procedures with sufficient accuracy were established for analysis of striae parameters such as striae periodicity and variations. Our ultrasonic method should be standardized as a new evaluation method not only for development of the EUVL-grade glass and evaluation of the production processes, but also for quality control and selection of the production lots.

The evaluation of periodic striae layers in TiO2-SiO2 ultra-low-expansion glasses, formed during production, is discussed through the measurement of leaky surface acoustic-wave (LSAW) velocities by the line-focus-beam (LFB) ultrasonic material-characterization system, The averaging effect associated with an LSAW propagation region interacting with periodic striae on a specimen surface was examined at 225 MHz, taking several specimens prepared with inclination angles of theta = 0,.2, 5, 10, 20, and 90 degrees to the plane of striae layers with a periodicity of 0.16 mm. LSAW velocities corresponding to TiO2 concentrations in the glass were properly measured for the specimens with 0 less than 10 degrees, and the perpendicular specimen (theta = 90 degrees) was suitable for accurate determination of the striae periodicities for LSAW propagation perpendicular to the striae plane.

Experimental procedures and standard specimens for characterizing and evaluating TiO2-SiO2 ultralow expansion glasses with periodic striae using the line-focus-beam (LFB) ultrasonic material characterization system are discussed. Two types of specimens were prepared, with specimen surfaces parallel and perpendicular to the striae plane using two different grades of glass ingots. The inhomogeneities of each of the specimens were evaluated at 225 MHz. It was clarified that parallel specimens are useful for accurately measuring velocity variations of leaky surface acoustic waves (LSAWs) excited on a water-loaded specimen surface associated with the striae. Perpendicular specimens are useful for obtaining periodicities in the striae for LSAW propagation perpendicular to the striae plane on a surface and for precisely measuring averaged velocities for LSAW propagation parallel to the striae plane. The standard velocity of Rayleigh-type LSAWs traveling parallel to the striae plane for the perpendicular specimens was numerically calculated using the measured velocities of longitudinal and shear waves and density. Consequently, a reliable standard specimen with an LSAW velocity of 3308.18 +/- 0.35 m/s at 23 degrees C and its temperature coefficient of 0.39 (m/s)/degrees C was obtained for a TiO2-SiO2 glass with a TiO2 concentration of 7.09 wt%. A basis for the striae analysis using this ultrasonic method was established.

Striae configurations in TiO2-SiO2 ultrd-low-expansion glasses caused by variations in TiO2 concentration were investigated through measurement of leaky surface acoustic wave (LSAW) velocities by the line-focus-beam (LFB) ultrasonic material characterization system. LSAW velocity distributions were measured on the surface of a specimen substrate prepared from a large circular plate glass ingot produced by the direct method using a flame hydrolysis process. A subsequent procedure that included polishing the surface of the specimen to reduce the specimen thickness by 40 mu m and measuring the LSAW velocity distributions on the surface was repeated five times in order to examine at least one period of the striae. TiO2 concentration variations were clearly observed in the deposit direction of the glass ingot and in its radial direction: The maximum LSAW velocity difference over the whole examined region was 11.7 m/s, corresponding to 0.70 wt % TiO2 concentration. The three-dimensional striae structure revealed that the striae plane in the examined region was almost parallel to the substrate surface but gently curved down in the radial direction. The plane had a slightly convex-shaped cross section layered with a striae periodicity of about 0.16 mm and a curvature radius of about 440 mm, and also existed in a circular form with a curvature radius of about 450 mm. The ultrasonic method will contribute to improvement of characteristics and homogeneity of glass associated with production-process conditions.

Measurement accuracies of leaky surface acoustic wave (LSAW) velocities for materials with highly attenuated waveforms of V(z) curves obtained-by the line-focus-beam ultrasonic material characterization (LFB-UMC) system are investigated. Theoretical investigations were carried out and experiments were performed for TiO2-SiO2 glass (C-7972), Li2O-Al2O3SiO2 glass ceramic (Zerodur (R)), and (111) gadolinium gallium garnet (GGG) single crystal as specimens. Waveform attenuations of V(z) curves for C-7972 and Zerodur are greater than those for the (111) GGG single crystal. Frequency dependences of the waveform attenuations were calculated for each specimen by considering the propagation attenuation of LSAWs. The theoretical results revealed that the waveform attenuation dominantly depends upon the acoustic energy loss due to the water loading effect on the specimen surface, and that the waveform attenuation becomes smaller with decreasing frequency. Significant improvement of the measurement precision of LSAW velocities was demonstrated for each specimen using three LFB ultrasonic devices with different curvature radii R of the cylindrical acoustic lenses: R = 2.0 mm at 75 MHz, R = 1.5 mm at 110 MHz, and R = 1.0 mm at 225 MHz; for C-7972, the precisions were improved from +/- 0.0053% at 225 MHz to +/- 0.0020% at 75 MHz.

We obtained an accurate relationship between the leaky surface acoustic wave (LSAW) velocities and TiO2 concentrations. Such a relationship is needed for the line-focus-beam ultrasonic material characterization (LFB-UMC) system as a new technology for evaluating the coefficient of thermal expansion (CTE) of ultra-low-expansion glasses with extremely high precision. Using commercially available TiO2-SiO2 glass with periodic striae, averaged velocities for LSAW propagation parallel to the striae plane at 225 MHz and averaged TiO2 concentrations by X-ray fluorescence analysis were measured on the surface of seven specimen substrates prepared perpendicular to the striae plane. The obtained sensitivity of LSAW velocity to TiO2 concentration was -0.0601 wt %/(m/s), and the measurement resolution was estimated to be 0.0084 wt % for +/- 2 sigma (sigma: standard deviation) from the LSAW velocity measurement resolution of 0.14 m/s. The TiO2 concentration for the standard TiO2-SiO2 glass specimen with a LSAW velocity of 3308.18 m/s for system calibration was determined to be 7.09 wt %. This ultrasonic technology will contribute greatly to the development of the ultra-low-expansion glasses needed for extreme ultraviolet lithography (EUVL) systems.

Super accurate evaluation method for TiO2-doped SiO2 ultra-low-expansion glass having periodic striae associated with its fabrication process was investigated using the line-focus-beam ultrasonic material characterization (LFB-UMC) system. To obtain absolute values of leaky surface acoustic wave (LSAW) velocities measured with the LFB-UMC system, proper standard specimens of the glass for system calibration was examined. Using a specimen with a surface perpendicular to the striae plane as the standard specimen, a reliable standard LSAW velocity of 3308.18 m/s within 0.35 m/s for the calibration was obtained regardless of influence of velocity variations due to the periodic striae. Also, we determined the accurate relationship between the TiO2 concentrations and LSAW velocities (sensitivity: -0.0601 wt%/(m/s)) so that the TiO2 concentration of the standard specimen with a LSAW velocity of 3308.18 m/s was determined to be 7.09 wt%. Furthermore, to evaluate more reliably the more homogeneous ultra-low-expansion glasses in the near future, the measurement accuracy of the LSAW velocity was improved with a method using the LFB device with a larger curvature radius R operating at lower frequency from +/- 0.0053% for R=1.0 mm at 225 MHz to +/- 0.0020% for R=2.0 mm at 75 MHz.

We developed experimental procedures to evaluate glass materials using the line-focus-beam ultrasonic-material-characterization (LFB-UMC) system. We prepared 28 specimens of a commercial borosilicate glass from random lots, and measured the velocities of leaky-surface acoustic waves (LSAWs) and leaky-surface-skimming compressional waves (LSSCWs), V-LSAW and V-LSSCW, using V(z) curve measurements at 225 MHz and 23 degrees C. The velocities for V-LSAW ranged from 3121.83 m/s to 3149.77 m/s, with a maximum deviation of 27.94 m/s. The velocities for VLSSCW ranged from 5547.7 m/s to 5585.0 m/s, with a maximum deviation of 37.3 m/s. To investigate these observed variations in V-LSAW and V-LSSCW, we measured the bulk acoustic wave (BAW) properties, viz., longitudinal and shear velocities, then the densities and the chemical compositions of 8 of the 28 specimens. The LFBUMC measurements confirmed that decreases in V-LSAW and V-LSSCW occur mainly with the B2O3 dopant concentrations, corresponding to the decrease of shear-wave and longitudinal-wave velocities that are caused by the decrease of the stiffness constants c(44) and c(11), respectively, rather than with decreased densities. The sensitivities are -6.36 X 10(-2) wt%/(m/s) for V-LSAW and -4.87 X 10-2 wt%/(m/s) for V-LSSCW. This demonstrates that the LFB-UMC system is effective for evaluating glass materials and controlling production processes, by analyzing variations in chemical composition through the super-accurate velocity measurements of LSAWs and LSSCWs.

A super-precise method of evaluating the coefficient of thermal expansion (CTE) of ultra-low-expansion glasses for future extreme ultra-violet lithography (EUVL) systems was developed using the line-focus-beam ultrasonic material characterization (LFB-UMC) system. Evaluation was demonstrated for two commercial glasses, TiO(2)-SiO(2) glass (C-7971) and Li(2)O-Al(2)O(3)-SiO(2) glass ceramic (Zerodur). For the C-7971 specimens, the sensitivity and resolution in the velocity measurement of leaky surface acoustic waves (LSAWs) for the CTE were estimated to be 4.40 (ppb/K)/(m/s) and +/- 0.77 ppb/K for +/- 2 sigma (sigma: standard deviation). LSAW velocity differences caused by different TiO(2) concentrations and distributions or striae in each specimen were successfully detected and evaluated. For the Zerodur specimens, LSAW velocity differences associated with the chemical compositions and crystallization conditions were observed among different ingots and specimens. This ultrasonic method is expected to be an extremely useful and effective CTE evaluation technology and to contribute to improving and developing EUVL-grade glass materials.

A super-precision evaluation method of the coefficient of thermal expansion (CTE) of ultra-low expansion glasses was developed using the line-focus-beam ultrasonic material characterization (LFB-UMC) system. Evaluation was demonstrated for TiO2-SiO2 glass. The sensitivity and resolution in the velocity measurement of leaky surface acoustic waves (LSAWs) in CTE were estimated to be 4.40 (ppb/K)/(m/s) and +/- 0.77 ppb/K for +/- 2 sigma (sigma: standard deviation) at 225 MHz. LSAW velocity differences caused by different TiO2 concentrations and distributions or striae in the specimens were successfully detected and evaluated, providing two-dimensional information under the nondestructive and noncontact measurement condition. This ultrasonic method is much more accurate than conventional methods, for evaluating CTE on the surface of ultra-low-expansion glass materials needed for extreme ultra-violet lithography (EUVL) systems.

A method of improving the measurement accuracy of leaky surface acoustic wave (LSAW) velocity for TiO2-doped SiO2 ultra-low-expansion glass using the line-focus-beam ultrasonic material characterization (LFB-UMC) system was investigated theoretically and experimentally. The frequency dependence of the interference waveform attenuation in a V(z) Curve obtained for the glass was calculated by considering the propagation attenuation of LSAWs. The theoretical results revealed that the waveform attenuation depends primarily on acoustic energy loss due to the water-loading effect on the specimen surface, and that the waveform attenuation decreases with decreasing frequency. Significant improvement of the measurement accuracy was successfully demonstrated by using an LFB ultrasonic device with a larger curvature radius R of the cylindrical sapphire acoustic lens, R = 2.0 mm, yielding an improved value of +/- 0.0020% obtained at 75 MHz, as compared to +/- 0.0053% obtained at 225 MHz with a cylindrical lens of R = 1.0 mm.

A super-precise method of evaluating the coefficient of thermal expansion (CTE) of ultra-low-expansion glasses was developed using the line-focus-beam ultrasonic material characterization (LFB-UMC) system and was demonstrated for TiO2-doped SiO2 glass. The sensitivity and resolution in the velocity measurement of leaky surface acoustic waves (LSAWs) in CTE were estimated to be 4.40 (ppb/K)/(m/s) and +/-0.77 ppb/K for +/-2sigma (sigma: standard deviation) at 225 MHz. LSAW velocity differences caused by different TiO2 concentrations and distributions or striae in the specimens were successfully detected and evaluated, providing two-dimensional information. This ultrasonic method is effective for evaluating ultra-low-expansion glasses needed for extreme ultra-violet lithography (EUVL) systems.

Langasite-type single crystal Ca3NbGa3Si2O14 (CNGS) was grown by the Czochralski technique. Dielectric, elastic and piezoelectric constants of CNGS were measured by the resonance-antiresonance method. At room temperature, dielectric constants epsilon(11)(T)/epsilon(0) and epsilon(33)(T)/epsilon(0) were 17.8 and 27.9, respectively. Electromechanical coupling coefficients k(12), k(25) and k(26) were also determined as 10.9, 17.3 and 11.9%, respectively. The measurements were carried out in a temperature range from -30 to 80 C. Temperature coefficients of the dielectric, elastic and piezoelectric constants were obtained. The line-focus-beam and plane-wave ultrasonic material characterization system was employed for measuring bulk acoustic velocities, and longitudinal and transverse wave velocities of 7408.4 m/s and 3136.2 m/s, respectively, in the c-direction uncoupled with piezoelectricity at 23 degreesC were obtained. This was in good agreement with the results determined by the resonance-antiresonance method. The density of CNGS was 4125 kg/m(3). All the parameters of the CNGS crystal for bulk and surface acoustic wave applications were determined in this research.

The effective radius of a bulk-wave ultrasonic transducer as a circular piston source, fabricated on one end of a synthetic silica (SiO2) glass buffer rod, was evaluated for accurate velocity measurements of dispersive specimens over a wide frequency range. The effective radius was determined by comparing measured and calculated phase variations due to diffraction in an ultrasonic transmission line of the SiO2 buffer rod/water-couplant/SiO2 standard specimen, using radio-frequency (RF) tone burst ultrasonic waves. Fourteen devices with different device parameters were evaluated. The velocities of the nondispersive standard specimen (C-7940) were found to be 5934.10 +/- 0.35 m/s at 70 to 290 MHz, after diffraction correction using the nominal radius (0.75 mm) for an ultrasonic device with an operating center frequency of about 400 MHz. Corrected velocities were more accurately found to be 5934.15 +/- 0.03 m/s by using the effective radius (0.780 mm) for the diffraction correction. Bulk-wave ultrasonic devices calibrated by this experimental procedure enable conducting extremely accurate velocity dispersion measurements.

A general method was established for precisely measuring velocity dispersion and attenuation in solid specimens with acoustic losses in the very high frequency (VHF) range, using the complex-mode measurement method and the diffraction correction method. Experimental procedures were presented for implementing such a method and demonstrated this measurement method in the frequency range of 50-230 MHz, using borosilicate glass (C-7740) as a dispersive specimen and synthetic silica glass (C-7980) as a nondispersive standard specimen. C-7980 exhibited no velocity dispersion; velocity was constant at 5929.14 +/- 0.03 m/s. C-7740 exhibited velocity dispersion, from 5542.27 m/s at 50 MHz to 5544.47 m/s at 230 MHz with an increase of about 2 m/s in the measured frequency range. When frequency dependence of attenuation was expressed as alpha = alpha(o)f(beta), the results were as follows: alpha(o) = 1.07X 10(-16) s(2)/m and beta=2 for C-7980 and alpha(o)=5.16X 10(-9) s(1.25)/m and beta= 1.25 for C-7740. (C) 2003 Acoustical Society of America.

We prepared standard specimens for the line-focus-beam ultrasonic material characterization system to obtain absolute values of the propagation characteristics (phase velocity and attenuation) of leaky surface acoustic waves (LSAWs). The characterization system is very useful for evaluating and analyzing specimen surfaces. The calibration accuracy of these acoustic parameters depends on the accuracy of acoustical physical constants (elastic constants, piezoelectric constants, dielectric constants, and density) determined for standard specimens. In this paper, we developed substrates of nonpiezoelectric single crystals (viz., gadolinium gallium garnet [GGG], Si, and Ge) and an isotropic solid (synthetic silica [SiO2] glass) as standard specimens. These specimens can cover the phase velocity range of 2600 to 5100 m/s for Rayleigh-type LSAWs. To determine the elastic constants with high accuracy, we measured velocities by the complex-mode measurement method and corrected diffraction effects. Measurements of bulk acoustic properties (bulk wave velocity and density) were conducted around 23degreesC, and bulk wave velocities were obtained with an accuracy of within +/-0.004%. We clearly detected differences in acoustic properties by comparing the obtained results with the previously published values; the differences were considered to be due to differences of the specimens used. We also detected differences in acoustic properties among four SiO2 substrates produced by different manufacturers.

A line-focus-beam ultrasonic material characterization (LFB-UMC) system has been developed to evaluate large diameter crystals and wafers currently used in electronic devices. The system enables highly accurate detection of slight changes in the physical and chemical properties in and among specimens. Material characterization proceeds by measuring the propagation characteristics, viz., phase velocity and attenuation, of Rayleigh-type leaky surface acoustic waves (LSAWs) excited on the water-loaded specimen surface. The measurement accuracy depends mainly upon the translation accuracy of the mechanical stages used in the system and the stability of the temperature environment. New precision mechanical translation stages have been developed, and the mechanical system, including the ultrasonic device and the specimen, has been installed in a temperature-controlled chamber to reduce thermal convection and conduction at the specimen. A method for precisely measuring temperature and longitudinal velocity in the water couplant has been developed, and a measurement procedure for precisely measuring the LSAW velocities has been completed, achieving greater relative accuracy to better than +/-0.002% at any single chosen point and +/-0.004% for two-dimensional measurements over a scanning area of a 200-mm diameter silicon single-crystal substrate. The system was developed to address various problems arising in science and industry associated with the development of materials and device fabrication processes.

The loss and phase advance due to diffraction are experimentally observed by measuring the amplitude and phase of radio frequency (rf) tone burst signals in the VHF range, in an ultrasonic transmission line consisting of a buffer rod with an ultrasonic transducer on one end, a couplant of water, and a solid specimen of synthetic silica glass. The measured results agree well with the calculated results from the exact integral expression of diffraction. The diffraction effects on the velocity and attenuation measured in this frequency range and their corrections are investigated to realize more accurate measurements. It is shown that attenuation measurements are influenced by diffraction losses and can be corrected by numerical calculations, and that velocity measurements are affected by the phase advance caused by diffraction. This investigation demonstrates that, in complex-mode velocity measurements, in which the velocity is determined from the measured phase of the signals, the true velocity at each frequency can be obtained by correction using the numerical calculation of diffraction. Based on this result, a new correction method in amplitude-mode velocity measurements is also proposed. In this new method, the velocity is determined from the intervals of interference output obtained by sweeping the ultrasonic frequency for the superposed signals generated by the double-pulse method. Velocity may be measured accurately at frequencies in the Fresnel region, and diffraction correction is essential to obtain highly accurate values with five significant figures or more. (C) 2000 Acoustical Society of America. [S0001-4966(00)02408-5].

We investigated the velocity measurements of leaky surface acoustic waves (LSAW) by line-focus-beam (LFB) acoustic microscopy of thin specimens for which the waves reflected from the back surface of the specimen (back reflection) must be included in the measurement model. The influence of back reflection resulted in a serious problem in measurement accuracy of the apparent changes of measured velocities. Using several samples of thin synthetic silica glasses, the determination of LSAW velocity affected by the reflected waves and the relationship between the specimen thickness and the apparent velocity change with a periodic frequency interval in the frequency dependence of measured LSAW velocities are discussed in detail. Three useful methods for eliminating that influence are proposed and demonstrated: first, separating the radio frequency (RF) pulsed wave signal from the specimen surface and the pulses reflected from the back surface by reducing the RF pulse width; second, scattering acoustic waves from the roughened back surface; and third, taking the moving average of measured frequency characteristics of LSAW velocities. It is shown that, among these methods, the moving average method is the most useful and effective as a general means to eliminate the influence and to determine intrinsic velocity values because this method needs no specimen process and no system change, and the same conventional V(z) curve measurement and analysis can be employed.

The acoustical physical constants (elastic constant, piezoelectric constant, dielectric constant, and density) of commercial surface acoustic wave (SAW)-grade LiNbO3 and LiTaO3 single crystals were determined by measuring the bulk acoustic wave velocities, dielectric constants, and densities of many plate specimens prepared from the ingots. The maximum probable error in each constant was examined by considering the dependence of each constant on the measured acoustic velocities. By comparing the measured values of longitudinal velocities that were not used to determine the constants with the calculated values using the previously mentioned constants, we found that the differences between the measured and calculated values were 1 m/s or less for both LiNbO3 and LiTaO3 crystals. These results suggest that the acoustical physical constants determined in this paper can give the values of bulk acoustic wave velocities with four significant digits.

When line-focus-beam acoustic microscopy is applied to thin specimens, waves reflected from the back surface of the specimen cause a serious problem in measurement accuracy of measured leaky surface acoustic wave (LSAW) velocities. Experimental results show that the velocities vary not only with the employed ultrasonic frequency but also with the specimen thickness. A method of eliminating that influence using the moving average of the frequency dependence of LSAW velocities is proposed and demonstrated for a Z-cut 5-mol% MgO-doped LiNbO3 wafer specimen about 380-mu m thick.

Absolute accuracy of the line-focus-beam (LFB) acoustic microscopy system is investigated for measurements of the leaky surface acoustic wave (LSAW) velocity and attenuation, and a method of system calibration is proposed. In order to discuss the accuracy, it is necessary to introduce a standard specimen whose bulk acoustic properties, (e.g., the independent elastic constants and density) are measured with high accuracy. Single crystal substrates of gadolinium gallium garnet (GGG) are taken as standard specimens. The LSAW propagation characteristics are measured and compared with the calculated results using the measured bulk acoustic properties. Calibration is demonstrated for the system using two LFB acoustic lens devices with a cylindrical concave surface of 1-mm radius in the frequency range 100 to 300 MHz.