平田 慎之介

Abstract Purpose Quantitative diagnosis of the degree of fibrosis progression is currently a focus of attention for fatty liver in nonalcoholic steatohepatitis (NASH). However, previous studies have focused on either lipid droplets or fibrotic tissue, and few have reported the evaluation of both in patients whose livers contain adipose and fibrous features. Our aim was to evaluate fibrosis tissue and lipid droplets in the liver. Methods We used an analytical method combining the multi-Rayleigh (MRA) model and a healthy liver structure filter (HLSF) as a technique for statistical analysis of the amplitude envelope to estimate fat and fibrotic volumes in clinical datasets with different degrees of fat and fibrosis progression. Results Fat mass was estimated based on the non-MRA fraction corresponding to the signal characteristics of aggregated lipid droplets. Non-MRA fraction has a positive correlation with fat mass and is effective for detecting moderate and severe fatty livers. Progression of fibrosis was estimated using MRA parameters in combination with the HLSF. The proposed method was used to extract non-healthy areas with characteristics of fibrotic tissue. Fibrosis in early fatty liver suggested the possibility of evaluation. On the other hand, fat was identified as a factor that reduced the accuracy of estimating fibrosis progression in moderate and severe fatty livers. Conclusion The proposed method was used to simultaneously evaluate fat mass and fibrosis progression in early fatty liver, suggesting the possibility of quantitative evaluation for discriminating between lipid droplets and fibrous tissue in the early fatty liver.

Abstract The basic concept of distance measurement using the alternate transmission of two different codes based on the pulse-echo method has been used to obtain an extension of the measurable distance, in which the temporal resolution is not degraded in the one-code transmission. In the alternate transmission, the reflected signals from the object are measured by two correlation signals. The received signal is correlated with each transmitted signal. The truncation and truncated interference noise of signals are generated in the cross-correlation function. Which is a part of the signal components. The signal components are changed according to the transmit signal. In this paper, the signal-to-noise ratio (SNR) of the alternate transmission of the different chirp signals is described and investigated. The highest SNR of the alternate chirp signal is achieved by the high bandwidth and long length of the transmitted signal. Moreover, the different bandwidth of the chirp transmission is simulated. The SNRs of the alternate transmission of different chip signals between the experiment and simulation are compared.

Introduction: Assessing the stage of liver fibrosis during the diagnosis and follow-up of patients with diffuse liver disease is crucial. The tissue structure in the fibrotic liver is reflected in the texture and contrast of an ultrasound image, with the pixel brightness indicating the intensity of the echo envelope. Therefore, the progression of liver fibrosis can be evaluated non-invasively by analyzing ultrasound images. Methods: A convolutional-neural-network (CNN) classification of ultrasound images was applied to estimate liver fibrosis. In this study, the colorization of the ultrasound images using echo-envelope statistics that correspond to the features of the images is proposed to improve the accuracy of CNN classification. In the proposed method, the ultrasound image is modulated by the 3rd- and 4th-order moments of pixel brightness. The two modulated images and the original image were then synthesized into a color image of RGB representation. Results and Discussion: The colorized ultrasound images were classified via transfer learning of VGG-16 to evaluate the effect of colorization. Of the 80 ultrasound images with liver fibrosis stages F1–F4, 38 images were accurately classified by the CNN using the original ultrasound images, whereas 47 images were classified by the proposed method.

Abstract Previous studies have shown that shear wave elastography of liver tissue can be unstable due to factors such as uncertainties in the acoustic radiation force (ARF) irradiation due to the influence of tissues near the surface and the complexity of the liver’s structure and its physical properties. This study aims to verify the influence of near-surface tissues on ARF and the effect of tissue structure on shear wave propagation and shear wave velocity (SWV) evaluation using the wave propagation simulations by the elastic finite-difference time domain method. It is found that the ARF becomes weakly focused on multiple locations due to refraction of longitudinal waves by near-surface tissues, and multiple shear waves of small amplitude are propagated. However, a macroscopic SWV assessment, as in clinical practice, reduces the influence of near-surface tissues because the microscopic assessment results are averaged over the near-surface tissues.

Abstract We attempted to visualize a single microbubble driven by acoustic radiation force using a combination of pulse inversion Doppler and plane wave imaging. Commercial microbubbles, Sonazoid^® underwent ultrasound exposure with a center frequency of 5.2 MHz, a pulse repetition frequency of 4 kHz, and a negative peak sound pressure of 1.59 MPa. It succeeded in separately detecting individual microbubbles with high sensitivity. The disappearance of freely-translating microbubbles could be observed as a broadened spectrum of Doppler signal, i.e. a pseudo-Doppler effect. However, the trend was not apparent in the case of wall-colliding microbubbles.

Abstract We compared the evaluation accuracy of amplitude envelope statistics under the transmission and reception conditions of compounded plane wave imaging (CPWI) and focused beam imaging (FBI). In a basic study using a homogeneous phantom, we found that the amplitude gradient in the depth direction and the point spread function in the lateral direction spread in the FBI reduced the accuracy of evaluation in amplitude envelope statistics. On the other hand, CPWI showed a more stable evaluation than FBI because of the elimination of sound field characteristics. In CPWI, the multi-Rayleigh model discriminated signals from two types of scatterer with high accuracy in the evaluation using phantoms mimicking fatty liver. It was confirmed that the combination of CPWI and the multi-Rayleigh model is effective for detecting early fatty liver disease. The results show that CPWI is effective for improving the robustness of amplitude envelope statistics.

Abstract In contrast enhancement ultrasound (CEUS), the vasculature image can be formed from nonlinear echoes arising from microbubbles in a blood flow. The use of binary-coded pulse compression is promising for improving the contrast of CEUS images by suppressing background noise. However, the amplitudes of nonlinear echoes can be reduced, and sidelobes by nonlinear echoes can occur depending on the binary code. Optimal Golay codes with slight nonlinear-echo reduction and nonlinear sidelobe have been proposed. In this study, CEUS images obtained by optimal Golay pulse compression are evaluated through experiments using Sonazoid microbubbles flowing in a tissue-mimicking phantom.

Abstract In sound wave propagation in the sea, it is important to evaluate the characteristics of sound reflection from the sea surface. The amplitude and phase of reflected sound waves fluctuate because of the changing sea surface with waves. In this study, using the finite difference time domain method and experiments in a water tank, we evaluated the variability characteristics of reflected sound waves on the sea surface generated by the Bretschneider-Mitsuyasu spectrum observed on the deep offshore coast of Japan. We introduced the concept of effective roughness of the sea surface and evaluated the variability characteristics of reflected sound waves on the sea surface. We confirmed the Rice distribution could express the amplitude variability, and the energy ratio γ is determined by the Rayleigh roughness parameter $2k{\sigma }_{z0},$ defined by the effective roughness ${\sigma }_{z0}$

Abstract In a previous study, an annular-array transducer was employed to characterize homogeneous scattering phantoms and excised rat livers using backscatter envelope statistics and frequency domain analysis. A sound field correction method was also applied to take into account the average attenuation of the entire scattering medium. Here, we further generalized the evaluation of backscatter coefficient (BSC) using the annular array in order to study skin tissues with a complicated structure. In layered phantoms composed of two types of media with different scattering characteristics, the BSC was evaluated by the usual attenuation correction method, which revealed an expected large difference from the predicted BSC. In order to improve the BSC estimate, a correction method that applied the attenuation of each layer as a reference combined with a method that corrects based on the attenuation of the analysis position were applied. It was found that the method using the average attenuation of each layer is the most effective. This correction method is well adapted to the extended depth of field provided by an annular array.

Abstract This study investigates how the translational velocity of phospholipid-coated bubbles caused by acoustic radiation force depends on their size. The translations of bubbles with mean radii of 0.9–5 μm were experimentally evaluated at five ultrasound frequency conditions (3.5, 5, 7.5, 10, and 15 MHz). We compared experimental data with theoretical prediction using a viscoelastic interfacial rheological model and a model suitable for high amplitude oscillation. The results suggested that the translation of bubbles could be enhanced for a mean radius of 1–3 μm but echo intensity could not.

Abstract In medical ultrasound imaging using microbubbles (MBs), the nonlinear echoes from the MBs are used for contrast-specific image construction. Techniques such as pulse inversion, amplitude modulation, and the combined method (PIAM) are employed to increase nonlinear components in the echoes. In addition, employment of pulse compression using binary-coded ultrasound can potentially increase the components. In the case of the nonlinear echo, however, a nonlinear sidelobe occurs around the compressed pulse (correlation peak), and nonlinear components for PIAM in the correlation peak are reduced. The shape of the nonlinear sidelobe and the nonlinear-component reduction in the correlation peak can be estimated from the binary codes used. In this study, the optimal binary codes for PIAM are determined from all patterns of 10, 16, and 20 bit Golay codes. Then, the performance of PIAM with pulse compression using each code is evaluated via computer simulations and experiments using the SonoVue MBs.

In previous studies, the double-Nakagami (DN) model has been proposed for fatty liver assessment and applied to in vivo rat livers and clinical data sets. The healthy liver structure filter (HLSF) method, which extracts non-healthy areas using two DN parameters, has also been proposed. In this paper, we first verify the accuracy of the DN model and the HLSF method for acoustic fields at 15 and 5 MHz, which were reproduced using numerical simulation. We then apply the method to clinical data sets of livers observed using a frequency of 3 MHz and investigate the method's clinical usefulness. A positive correlation (r = 0.28) was found between the ratio of the non-healthy area and fat mass. Although the results were inferior to the results produced using 15 MHz ultrasound (r = 0.96), we found that it was possible to detect the difference between a normal liver and a fatty liver even at a lower frequency. (C) 2021 The Japan Society of Applied Physics

<p>目的：慢性肝疾患は，長期に渡る治療中に注意深い経過観察が必要であり，超音波イメージングシステムに基づく肝線維化の定量的診断法の開発が強く期待されている．方法：同時生起行列を使用したテクスチャ解析を，線維化肝の臨床超音波画像と超音波シミュレーション画像両方に応用した．画素間距離rに対し一連の同時生起行列が生成され，テクスチャ特徴量コントラストを選択し，マルチレイリーモデルを使用したエコー振幅分布の統計的分析と組み合わせて，rに対する応答を観察した．結果：臨床超音波画像と超音波シミュレーション画像両方において線維化が進行するにつれ，コントラストは大きな値に収束し，rに対する応答に大きな揺らぎが見られた．収束値は，線維化の初期段階で急速に上昇し，揺らぎは線維化の進行期で大きくなった．既知の線維組織構造に対する超音波シミュレーション画像を用いた解析により，コントラストの挙動と線維化の進行との関係性を理論的に明らかにした．結論：コントラストの収束値と揺らぎが，線維組織構造に関する情報を提供することが明らかになり，これらのデータが肝線維化の進行度の定量診断に利用されることが期待される．</p>

A method of ultrasonic position and velocity measurements for a moving object by M-sequence pulse compression has been proposed. In the proposed method, the Doppler velocity is estimated from the peak in the autocorrelation function of the received signal, which includes cyclic M-sequences reflected from the object. Then, the received signal is correlated with the reference M-sequence expanded or compressed in accordance with the estimated Doppler velocity. The position is determined from the acoustic image formed from cross-correlation functions obtained in different propagation paths of ultrasound. In this paper, the simultaneous transmission of preferred-pair M-sequences is studied to improve the spatial resolution of the image while keeping the original frame rate of the proposed method. Experiments using the moving pole, two loudspeakers and three microphones are conducted to evaluate the estimated Doppler velocities and determined positions. In most situations, Doppler velocities can be accurately estimated when two different Doppler components are included in the received signal. In some situations, however, accurate Doppler velocities inevitably cannot be estimated due to the peak overlapping in the autocorrelation function. The accuracy of determined positions may degrade when the signal-to-noise ratio of the received signal is insufficient or Doppler velocities are not accurately estimated.

M-sequence pulse compression is one of the typical techniques of distance measurement by the time of flight (TOF) of ultrasound. In the cross-correlation function (CCF) between the received signal and the transmitted M-sequence code, a sharp peak occurs at the time corresponds to the TOF. The limit of the measurable TOF corresponds to the maximum measurable distance is determined by the length of the M-sequence coded ultrasound. Furthermore, there is a trade-off between the measurable distance and the temporal resolution of the measurement. The alternate transmission of two different codes in M-sequence pulse compression has been proposed to extend the measurable distance to double with keeping the temporal resolution in the one-code transmission of the M-sequence. However, truncation and truncated interference noises are generated around sharp peaks and make it difficult to identify sharp peaks. Amplitudes or shapes of these noises are varied by the combination of M-sequences. Therefore, the selection of suitable combination of M-sequences can suppress the effect of these noises.

Functional measurement techniques and noncontact measurement techniques using ultrasound have been widely studied. However, only a few studies have addressed the possibility of noncontact elasticity measurements using airborne ultrasound. In this paper, we propose a novel noncontact measurement method that uses a high-frequency airborne ultrasonic transducer operating at 1 MHz. First, the fundamental characteristics of the proposed high-frequency airborne ultrasonic transducer were quantified both numerically and experimentally. Second, to validate the proposed method, experimental viscoelasticity estimations were performed. Young's moduli and viscosity coefficients of three tissue-mimicking phantoms (Young's moduli: 30 kPa with/without viscosity, 70 kPa) and chicken tissue samples were estimated using a piezoelectric actuator and the proposed airborne ultrasonic transducer. The estimated Young's moduli and viscosity agreed with the reference values. Thus, the proposed system can be used for noncontact measurements of elasticity. (C) 2020 The Japan Society of Applied Physics

We have been developing a quantitative estimation method of liver fibrosis using the multi-Rayleigh model to express a probability density function of the echo envelope. In the estimation, a combination of moments of the echo amplitude is used as input to estimate model parameters. To realize a robust quantification of liver fibrosis stage, we searched for the optimal combination of moments in the complex space. By using the estimated results in the multi-Rayleigh model parameters' space, we found the optimal combination of moments in real and imaginary spaces that can improve the estimation accuracy of multi-Rayleigh model parameters. From the results of the accuracy analysis, it was found that it is difficult to estimate the mixture ratio for the early stage of fibrosis even if the optimal combination of moments is used. However, estimation of the variance ratio is accurate enough to quantify fibrosis and can provide useful information. It became clear that the quantification method using the multi-Rayleigh model is effective. (C) 2020 The Japan Society of Applied Physics

In M-sequence pulse compression for acoustic distance measurement, a continuous signal modulated by the cyclic binary code in an M-sequence is transmitted. Then, the received signal is correlated with one cycle of the transmitted code. The time of flight for the estimation of the propagation distance is determined from the peak appeared in the cross-correlation function when both codes match. The temporal resolution of the measurement and the maximum measurable distance are determined by the cycle length of the transmitted signal and in a trade-off relationship. Alternate transmission of different M-sequence codes and cross-correlations with each code can extend the measurable distance without degradation of the temporal resolution. However, truncation noise in each code and truncated interference noise between codes are generated around correlation peaks. The patterns of these noises are varied by the combination of codes. Therefore, contamination by these noise can be suppressed by selecting suitable codes. (C) 2019 The Japan Society of Applied Physics

Many kinds of hydroacoustic devices are used in the field of ocean development of resources and observations. In evaluating the effect of sound propagation in water, it is important to evaluate the characteristics of sound reflection on sea surface. Amplitude and phase of reflected sound waves often fluctuates because of the changing sea surface with waves. In this paper, we evaluated the amplitude and phase variability characteristics of reflected sound waves on sea surface by acoustic simulation with the finite difference time domain method and water tank test. It is revealed that the energy ratio. for amplitude variability is uniquely determined by Rayleigh roughness parameter 2k sigma(z) when the sea surface is sufficiently random or the number of surface waves 2L/Lambda included in the irradiation range of sound waves is large. In addition, the standard deviation of phase sigma(theta) for the phase variability is determined by 2k sigma(z) regardless of Lambda, that is, sea surface spectrum. (C) 2019 The Japan Society of Applied Physics

Measurement of ultrasonic propagation characteristics in cancellous bone is one of the diagnosis methods of osteoporosis. In the examination, ultrasonic transducers are typically brought into contact with heel sides through an ultrasonic gel to effectively propagate ultrasound. Non-contact measurement of the speed of sound (SOS) in a heel using airborne ultrasound which passed through the heel has been proposed to enable the easy-repeatable and low-cost examination. However, the accuracy of the proposed method hasn't been sufficient in the measurement of agar phantoms or actual heels. The SOS is estimated based on determination of the time of flight (TOF) and measurement of the propagation path of ultrasound. Therefore, TOF determination and path-length measurement in the proposed method are improved. Then, SOS measurement for the parallel-sides agar phantom is evaluated.

The development of a quantitative diagnostic method for liver fibrosis using an ultrasound B-mode image is highly required. In our previous study, a multi-Rayleigh model was proposed to express a probability distribution of echo envelope amplitude from a fibrotic liver. Using the multi-Rayleigh model, a structure of fibrotic tissue can be quantitatively estimated. In this study, a method of estimating the number of tissue components was proposed to improve the accuracy of estimating a fibrotic tissue structure. Using threshold processing for a squared Mahalanobis distance of moments, which is a statistical property of echo envelope amplitude, the number of tissue components could be quantitatively estimated. The results of evaluation of clinical ultrasound B-mode images using the multi-Rayleigh model with estimation of the number of tissue components well reflected the tissue structural changes caused by liver fibrosis. It was concluded that our proposed method of estimating the number of tissue components improves the accuracy of liver fibrosis evaluation based on the multi-Rayleigh model. (C) 2018 The Japan Society of Applied Physics

The diagnosis of liver fibrosis using an ultrasound B-mode image has the advantages of real-time observation and noninvasive properties. We proposed a multi-Rayleigh model to express a probability density function (PDF) of echo envelope from a fibrotic liver. By using the multi-Rayleigh model, fibrotic parameters can be estimated. To quantitatively evaluate liver fibrosis using the multi-Rayleigh model, it is important to establish a high estimation accuracy method of multi-Rayleigh model parameters for clinical data. In this paper, by using the simulated ultrasound B-mode image, the relationship between the moments of echo data as input parameters for the evaluation of liver fibrosis based on the multi-Rayleigh model and the estimation accuracy of the multi-Rayleigh model parameters was examined. From the simulation results, we can determine the optimal combination of moments that can improve the estimation accuracy of the multi-Rayleigh model by focusing on the distribution of estimated values in the multi-Rayleigh model parameters' space. (c) 2018 The Japan Society of Applied Physics

Purpose Chronic liver disease requires careful follow-up during long-term treatment, and development of a quantitative diagnosis method for liver fibrosis based on an ultrasonic imaging system is highly desired.Methods Texture analysis using a co-occurrence matrix was applied to both clinical and simulated ultrasonic images of fibrotic livers. A sequence of matrices was generated for pixel-pair distance, r, and texture feature contrast was chosen to examine the response to r in combination with statistical analysis of echo amplitude distribution using a multi-Rayleigh model.Results The contrast converged with a larger value and fluctuated more significantly in response to r as fibrosis progressed in both the clinical and simulated ultrasonic images. The convergent value rapidly increased at the early stage of fibrosis, and the fluctuation became larger at the advanced stage of fibrosis. Analysis using simulated ultrasonic images with a known fibrous tissue structure theoretically clarified the relationship between contrast behavior and fibrosis progression.Conclusion It was revealed that contrast convergent value and contrast fluctuation provided information on the fibrous tissue structure, and they are expected to be used for quantitative diagnosis of the degree of liver fibrosis.

A diagnosis of liver fibrosis using an ultrasound B-mode image has the advantages of real-time observation and noninvasive properties. In our previous study, a multi-Rayleigh model was proposed to express a probability density function (PDF) of echo amplitudes from a fibrotic liver. From the multi-Rayleigh model, fibrosis parameters, such as the amount of fibrotic tissue and its progressive ratio, can be extracted. To quantitatively evaluate liver fibrosis using the multi-Rayleigh model, it is important to evaluate the stability of the estimation method of multi-Rayleigh model parameters. In this study, a numerical simulation using random variables following the multi-Rayleigh model was performed and the estimation stability of the parameters of the multi-Rayleigh model with two components was examined. From the simulation results, it was found that estimation becomes unstable under a certain condition owing to statistical variations of moments, which are inputs in the estimation algorithm. The instability of estimated parameters could be evaluated by focusing on changes in moments upon changes in multi-Rayleigh model parameters. It was indicated that we can evaluate the reliability of the estimated parameters of the multi-Rayleigh model only from the estimated values. (C) 2016 The Japan Society of Applied Physics

Ultrasonic distance measurement for obstacles has been recently applied in automobiles. The pulse-echo method based on the transmission of an ultrasonic pulse and time-of-flight (TOF) determination of the reflected echo is one of the typical methods of ultrasonic distance measurement. Improvement of the signal-to-noise ratio (SNR) of the echo and the avoidance of crosstalk between ultrasonic sensors in the pulse-echo method are required in automotive measurement. The SNR of the reflected echo and the resolution of the TOF are improved by the employment of pulse compression using a maximum-length sequence (M-sequence), which is one of the binary pseudorandom sequences generated from a linear feedback shift register (LFSR). Crosstalk is avoided by using transmitted signals coded by different M-sequences generated from different LFSRs. In the case of lower-order M-sequences, however, the number of measurement channels corresponding to the pattern of the LFSR is not enough. In this paper, pulse compression using linear-frequency-modulated (LFM) signals coded by M-sequences has been proposed. The coding of LFM signals by the same M-sequence can produce different transmitted signals and increase the number of measurement channels. In the proposed method, however, the truncation noise in autocorrelation functions and the interference noise in cross-correlation functions degrade the SNRs of received echoes. Therefore, autocorrelation properties and cross-correlation properties in all patterns of combinations of coded LFM signals are evaluated. (C) 2016 The Japan Society of Applied Physics

This paper proposes a novel system for three dimensional - position and velocity measurements with echolocation. It is improved from the former systems, based on low computational one-bit signal processing, to have wider detectability from one and two dimensions to three dimensions with the rearrangement of the ultrasonic receiver positions. The proposed method can measure the object location from nonlinear equations without using iterative methods. This method can concurrently measure position and velocity in three dimensional spaces with one-time measurement. The sound radiation and reflection studies using echolocation are also included in this paper. The additive noise: White Gaussian Noise, Colored Gaussian Noise, General Gaussian Noise, Laplacian Noise, and Gaussian Mixture Noise, is considered for the performance study. The system consists of one sound transmitter and three receivers. These devices are simple sound packages to support low-cost applications. In addition, to satisfy the requirement for a low-computation cost, an echo is converted into a one-bit signal by a three-channel delta-sigma-modulation board. Then, FPGA is used to determine recursive cross correlation based on one-bit computation. The object location is then defined with x-y-z coordinates. The object's velocity is computed using linear-period-modulated signals. The validity and repeatability of experimental results are evaluated using statistics. (C) 2015 Elsevier B.V. All rights reserved.

In medical ultrasonic images of liver disease, a texture with a speckle pattern indicates a microscopic structure such as nodules surrounded by fibrous tissues in hepatitis or cirrhosis. We have been applying texture analysis based on a co-occurrence matrix to ultrasonic images of fibrotic liver for quantitative tissue characterization. A co-occurrence matrix consists of the probability distribution of brightness of pixel pairs specified with spatial parameters and gives new information on liver disease. Ultrasonic images of different types of fibrotic liver were simulated and the texture-feature contrast was calculated to quantify the co-occurrence matrices generated from the images. The results show that the contrast converges with a value that can be theoretically estimated using a multi-Rayleigh model of echo signal amplitude distribution. We also found that the contrast value increases as liver fibrosis progresses and fluctuates depending on the size of fibrotic structure. (C) 2015 The Japan Society of Applied Physics

We have been developing a quantitative diagnostic method for liver fibrosis using an ultrasound image. In our previous study, we proposed a multi-Rayleigh model to express a probability density function of the echo amplitude from liver fibrosis and proposed a probability imaging method of tissue characteristics on the basis of the multi-Rayleigh model. In an evaluation using the multi-Rayleigh model, we found that a modeling error of the multi-Rayleigh model was increased by the effect of nonspeckle signals. In this paper, we proposed a method of removing nonspeckle signals using the modeling error of the multi-Rayleigh model and evaluated the probability image of tissue characteristics after removing the nonspeckle signals. By removing nonspeckle signals, the modeling error of the multi-Rayleigh model was decreased. A correct probability image of tissue characteristics was obtained by removing nonspeckle signals. We concluded that the removal of nonspeckle signals is important for evaluating liver fibrosis quantitatively. (C) 2015 The Japan Society of Applied Physics

Pulse compression using a maximum-length sequence (M-sequence) can improve the signal-to-noise ratio (SNR) of the reflected echo in the pulse-echo method. In the case of a moving object, however, the echo is modulated owing to the Doppler effect. The Doppler-shifted M-sequence-modulated signal cannot be correlated with the reference signal that corresponds to the transmitted M-sequence-modulated signal. Therefore, Doppler velocity estimation by spectrum-pattern analysis of a cyclic M-sequence-modulated signal and cross correlations with Doppler-shifted reference signals that correspond to the estimated Doppler velocities has been proposed. In this paper, measurements of the position and velocity of a moving object by the proposed method are described. First, Doppler velocities of the object are estimated using a microphone array. Secondly, the received signal from each microphone is correlated with each Doppler-shifted reference signal. Then, the position of the object is determined from the B-mode image formed from all cross-correlation functions. After that, the velocity of the object is calculated from velocity components estimated from the Doppler velocities and the position. Finally, the estimated Doppler velocities, determined positions, and calculated velocities are evaluated. (C) 2015 The Japan Society of Applied Physics

Recently, micro-droplet dispensation has been required in printed-electronics (PE) technology. Devices with micro dispensing mechanism are of key importance in achieving a higher performance with these products. In fact, it is very difficult for the conventional dispenser to squeeze highly viscous liquid with picoliter resolution. This paper describes the development of a dispensing mechanism comprising a dispensing device and XY stage, both driven by the piezo impulsive force. The dispensing device is mainly composed of a pipette and a taper needle that is driven by a piezoelectric element. When the needle passes through the pipette, a droplet of the liquid adheres to the needle-tip end. A micro droplet can be transcribed to a target surface by bringing the droplet at the needle-tip end in contact with the target surface. On the contrary, in the XY stage, the small tables on the V-shaped grooves can be driven by the impulsive force generated by the mass connected to the piezoelectric element. The X stage is stacked on the Y stage, which allows fine positioning in the plane. In the experiment, an array of a small amount of 0.2-picoliter droplets was successfully developed on the glass plate.

The coding of a transmitted signal by a maximum-length sequence (M-sequence) is employed in the pulse-echo method with pulse compression for ultrasonic distance measurement. To estimate the distance, the time of flight (TOF) of an echo is determined from the cross-correlation function between the received signal and the reference signal that corresponds to the transmitted signal. When codes of the received signal and the reference signal match, a high correlation value is obtained in the cross-correlation function. On the other hand, when they do not match, a low correlation value is obtained. In the case of the finite-length M-sequence code, however, truncation noise is generated at the beginning and end of the cross-correlation function. In this study, truncation noise in autocorrelation functions of all patterns of M-sequence codes is quantitatively evaluated from the 4th order to the 15th order. The peak amplitude and intensity of truncation noise vary depending on the patterns of M-sequence codes. Therefore, they can be reduced by selecting suitable M-sequence codes.