Yoshiki Nagatani

Kobe City College of Technology · Department of Electronics

The investigation of cancellous bone using ultrasound measurements is not an easy task due to the solid complex trabecular structure filled with fluid-like bone marrow. It is expected that the ultrasound propagated in cancellous bone contains valuable information about the complex structure. In this chapter, the methods to derive useful information...

Ultrasound can deliver speech information when it is amplitude-modulated with speech and presented via bone conduction. This speech-modulated bone-conducted ultrasound (SM-BCU) can also transmit prosodic information. However, there is insufficient research on the recognition of vowel duration in SM-BCU. The aim of this study was to investigate the...

In this study, a new research method using psychoacoustic experiments and acoustic simulations is proposed for human echolocation research. A shape discrimination experiment was conducted for sighted people using pitch-converted virtual echoes from targets of dissimilar two-dimensional (2D) shapes. These echoes were simulated using a three-dimensio...

The two-dimensional (2D) ultrasound imaging is widely used in several fields. In this study, the potential of two-dimensional ultrasound imaging technique based on machine learning is shown. A line transmitter was placed at one side and a receiver array was placed at the opposite side of the medium, respectively. The received signals at the receive...

A finite-difference time-domain (FDTD) technique was used to model the complex propagation of ultrasonic waves through the human radius. A three-dimensional model of the radius, including its uniaxial anisotropy and heterogeneity, was created using structural data obtained from high-resolution peripheral quantitative computed tomographic images. FD...

Echolocating bats exhibit sophisticated sonar behaviors using ultrasounds with actively adjusted acoustic characteristics (e.g., frequency and time-frequency structure) depending on the situation. In this study, the utility of ultrasound in human echolocation was examined. By listening to ultrasonic echoes with a shifted pitch to be audible, the pa...

Low intensity pulsed ultrasound can shorten the healing time of a bone fracture; however, the present technique does not seem not to consider the complicated ultrasound propagation in the body with bone. In this study, the time reversal technique was used to effectively converge ultrasound in the bone part. A three-dimensional distal radius model w...

Since bone has a complex structure, it is difficult to analytically understand the behavior of the ultrasound although it is useful for bone quality diagnosis. Our group, therefore, had been working on simulating ultrasound propagation inside bone models. In this paper, the results of the neural network based bone analysis using waveforms derived b...

Since the two-wave separating phenomenon of ultrasound in cancellous bone was found, the detailed behavior of two waves has been investigated in order to put the mechanism into practical use. However, it has been unclear whether the two-waves could be seen in in vivo situation where the cancellous bone is surrounded by cortical bone which has compl...

Degenerative discopathy is a common pathology which may require spine surgery. A metallic cylindrical pin is inserted into the vertebral body to maintain soft tissues and may be used as a reflector of ultrasonic wave to estimate bone density. The first aim of this paper is to validate a 3D model to simulate the ultrasonic propagation in a trabecula...

Ultrasound signals that pass through cancellous bone may be considered to consist of two longitudinal waves, which are called fast and slow waves. Accurate decomposition of these fast and slow waves is considered to be highly beneficial in determination of the characteristics of cancellous bone. In the present study, a fast decomposition method usi...

Ultrasound signal passing through cancellous bone consists of two longitudinal waves: fast and slow waves. Accurate decomposition of the fast and slow waves is supposed to be highly beneficial in order to determine the characteristics of cancellous bone. We applied a fast decomposition method using adaptive beamforming technique with a phase rotati...

Since bone has a complex structure, it is difficult to model analytically the behavior of ultrasound propagating in bone although ultrasound is useful for the diagnosis of not only bone density but also bone quality. Our group, therefore, had been working on simulating ultrasound propagation inside cancellous bones and models with cortical bones us...

Bats detect objects by echolocation. With those echoes, they can describe the shape of objects as well as position, and then approach or avoid them. To reveal which part of objects bats gaze at, we simulated the echoes that bats hear, and estimate the bats’ echolocated points by time-domain 2D-acoustic-simulation based on the behavioral data during...

Ultrasound propagation in a heterogeneous cortical bone was studied. Using a bovine radius, the longitudinal wave velocity distribution in the axial direction was experimentally measured in the MHz range. The bilinear interpolation and piecewise cubic Hermite interpolation methods were applied to create a three-dimensional (3D) precise velocity mod...

Degenerative discopathy is a common pathology that may require spine surgery. A metallic cylindrical pin is inserted into the vertebral body to maintain soft tissues and may be used as a reflector of ultrasonic wave to estimate bone density. The first aim of this paper is to validate a three-dimensional (3-D) model to simulate the ultrasonic propag...

The effect of the heterogeneity of the long cortical bone is an important factor when applying the axial transmission technique. In this study, the axial longitudinal wave velocity distributions in specimens from the mid-shaft of a bovine femur were measured, in the MHz range. Bilinear interpolation and the piecewise cubic Hermite interpolating pol...

Ultrasound propagation in the heterogeneous long cortical bone was studied. First, ring shaped specimens were obtained from the mid-shaft of a bovine radius. The longitudinal wave velocity distribution of each specimen was measured in the MHz range. Then, using the bilinear interpolation and the piecewise cubic Hermite interpolating method, a 3D ax...

Through-transmission measurements in cancellous bone in vitro often reveal two longitudinal waves. The velocities and amplitudes of fast and slow waves are related to bone microstructure and composition and may provide useful diagnostic information. Phase velocity and attenuation for fast and slow waves were measured as a function of propagation de...

Bone quality is an important parameter in spine surgery, but it remains difficult to be assessed clinically. The aim of this work is to demonstrate the feasibility of a QUS method to retrieve bone mechanical properties using an echographic technique taking advantage of the presence of a metallic pin inserted in bone tissue. To do so, an experimenta...

Since the cancelous bone inside long bones has porous structure, the acoustic wave propagating inside bone may bring us useful information for the diagnosis of osteoporosis or bone healing although it is difficult to be investigated. In this paper, simulation techniques for understanding the complex wave propagation will be presented. The three-dim...

The through-transmission ultrasound signal in cancelous bone consists of two longitudinal waves, called the fast and slow waves. The conventional propagation model assumes that the wavefront of an ultrasound wave passing through a bone specimen is flat and that each wave arrives simultaneously at all the points on a transducer surface. To compensat...

Bone quality is an important parameter in spine surgery, but its clinical assessment remains difficult. The aim of the work described here was to demonstrate in vitro the feasibility of employing quantitative ultrasound to retrieve bone mechanical properties using an echographic technique taking advantage of the presence of a metallic pin inserted...

Two longitudinal wave modes (called fast and slow wave modes) have been shown to propagate in cancellous bone. In this study, the effect of viscoelasticity on this two-wave phenomenon was investigated using a 3-D finite-difference time-domain (FDTD) method accounting for viscoelastic phenomena. The results show that the amplitude of the slow wave i...

The received signal in through-transmission ultrasound measurements of cancellous bone consists of two longitudinal waves, called the fast and slow waves. Analysis of these fast and slow waves may reveal characteristics of the cancellous bone that would be good indicators of osteoporosis. Because the two waves often overlap, decomposition of the re...

The ultrasonic axial transmission (AT) technique is known to assess the cortical bone of femur and tibia. After the first application of the finite difference time domain (FDTD) method [1], the wave propagation in bone has been discussed by both simulation and experimental studies. The wave propagation depends on the wave velocity, bone geometry (c...

The goal of this study was to compare the results from two proposed methods for separating fast and slow waves from mixed-mode signals, one using Bayesian probability theory and one using modified least-squares Prony’s (MLSP) [Wear, J. Acoust. Soc. Am. 133, 2490–2501 (2013)], on measurements of cancellous bone. Ultrasonic through-transmission data...

Control of vasospasm is one of the most important problems in postoperative management after the occurrence of subarachnoid hemorrhage. Transcranial Doppler ultrasonography (TCD) is a non-invasive test that measures cerebral blood flow. However, high-intensity interference returned from the cranium causes estimation errors. A moving target indicato...

Fast and slow waves were detected in a bovine cancellous bone sample for thicknesses ranging from 7 to 12 mm using bandlimited deconvolution and the modified least-squares Prony's method with curve fitting (MLSP + CF). Bandlimited deconvolution consistently isolated two waves with linear-with-frequency attenuation coefficients as evidenced by high...

Fast and slow waves were detected in a bovine cancellous bone sample for thicknesses ranging from 7 to 12 mm using bandlimited deconvolution and the modified least-squares Prony's method with curve fitting (MLSP+CF). Bandlimited deconvolution consistently isolated two waves with linear-with-frequency attenuation coefficients, as evidenced by high c...

An ultrasonic system is good for the evaluation of children because its noninvasiveness. The ultrasonic bone measurement system LD-100 has been developed on the basis of the principle of the fast and slow wave phenomenon in the wrist bone. In the measurement of small bones such as those of children, there are some problems due to the influences of...

Audible sound with a low-frequency vibration brings about hydrodynamic alignment of a supramolecular nanofiber in solution. Design of the nanoscale molecules and molecular assemblies, which can sense a wide range of frequencies of the audible sound wave with high sensitivity, develops sound-driven molecular machines and sound-responsive nanomateria...

The cover picture shows an image of the musical alignment of a supramolecular nanofiber, composed of an anthracene derivative, while the Kobe University Symphony Orchestra was playing classical music. In their Full Paper on page 516 ff., Akihiko Tsuda and co-workers report the quick and dynamic align of these nanofibers as a response to sensing aco...

Audible sound with a low-frequency vibration brings about hydrodynamic alignment of a supramolecular nanofiber in solution. Design of the nanoscale molecules and molecular assemblies, which can sense a wide range of frequencies of the audible sound wave with high sensitivity, develops sound-driven molecular machines and sound-responsive nanomateria...

An ultrasonic pulse propagating in cancellous bone can be separated into two waves depending on the condition of the specimen. These two waves, which are called the fast wave and the slow wave, provide important information for the diagnosis of osteoporosis. The present study proposes to utilize a signal processing method that extracts the instanta...

Speech-modulated bone-conducted ultrasound (BCU) can transmit speech sounds for some profoundly deaf individuals. Hearing aids using BCU are considered to be a novel hearing system for such individuals. In our previous study, the speech discrimination for speech-modulated BCU was objectively confirmed using a magnetoencephalography. Moreover, in ou...

The two-wave phenomenon, the wave separation of a single ultrasonic pulse in cancellous bone, is expected to be a useful tool for the diagnosis of osteoporosis. However, because actual bone has a complicated structure, precise studies on the effect of transition conditions between cortical and cancellous parts are required. This study investigated...

Fast and slow longitudinal waves can propagate through cancellous bone in the direction of the strong trabecular orientation. In in vivo experiments, the cortical bone layer surrounding cancellous bone is considered to affect the fast and slow wave propagations. In this study, the effects of the cortical bone layer were investigated using the strat...

Fast and slow longitudinal waves can propagate through cancellous bone in the direction of the strong trabecular orientation. In in vivo experiments, the cortical bone layer surrounding cancellous bone is considered to affect the fast and slow wave propagations. In this study, the effects of the cortical bone layer were investigated using the strat...

After the successful observation of two wave phenomenon in cancellous bone, wave characteristics have been investigated by in vitro studies. However, there still exists strong necessity to understand the effects of bone boundary conditions on the phenomenon, because the cancellous bone is always covered by a cortical layer in vivo. This paper is de...

Bayesian probability approach with a simple model was introduced for the analysis of two wave propagation phenomenon in the cancellous bone. The fast and slow waves could be estimated from the experimentally observed wave. The reproduced wave made by these estimated fast and slow waves was compared with the initial experimental wave using a wavelet...

The effects of overlapping fast and slow waves on measurements of the apparent attenuation as a function of propagation distance are investigated along with methods of analysis used to determine the attenuation properties. Two methods are applied to simulated data. The first method uses a time-domain approach that was dictated by constraints impose...

Previous studies have shown that interference between fast waves and slow waves can lead to observed negative dispersion in cancellous bone. In this study, the effects of overlapping fast and slow waves on measurements of the apparent attenuation as a function of propagation distance are investigated along with methods of analysis used to determine...

Ultrasound propagation in cancellous bone (porous media) under the condition of closed pore boundaries was investigated. A cancellous bone and two plate-like cortical bones obtained from a racehorse were prepared. A water-immersion ultrasound technique in the MHz range and a three-dimensional elastic finite-difference time-domain (FDTD) method were...

The two-wave phenomenon in a cancellous bone surrounded by a cortical bone was investigated using the specimens obtained from large mammals. Measurements were performed using laboratory-built poly(vinylidene fluoride) (PVDF) transducers excited by a one-cycle sinusoidal wave at 1 MHz. In addition to the experimental ultrasonic measurements, the fin...

Bone-conducted ultrasound (BCU) modulated by speech sound is recognized as speech sound and activates the auditory cortex similar to audible sound. To investigate the mechanisms of perception, the effects of stimulus duration on N1m were compared among air-conducted audible speech sound (AC speech), AC speech with carrier BCU and speech-modulated B...

Longitudinal wave in cancellous bone separates into fast and slow waves depending on the structure of bone trabeculae (two wave phenomenon). The fast wave strongly depends on the structure of bone trabeculae, and the velocity varies due to the structure and propagation direction. In this study, we measured changes of ultrasonic waves after the prop...

Cancellous bone consists of a complex solid trabecular network structure filled with soft bone marrow. The use of a short and broadband ultrasound incident pulse enables the experimental observation of a two longitudinal wave phenomenon, consistently with Biot's prediction for porous media. This chapter is a review of the experimental studies and d...

The question of whether sound vibration of a medium can bring about any kind of molecular or macromolecular events is a long-standing scientific controversy. Although it is known that ultrasonic vibrations with frequencies of more than 1 MHz are able to align certain macromolecules in solution, no effect has yet been reported with audible sound, th...

Ultrasonic waves targeted on cancellous bone separates into fast and slow waves according to the alignment of bone trabeculae. The characteristics of the specimen, however, can sometimes result in ambiguous wave separation. In this study, we proposed using wavelet transform as a new method of analyzing ultrasonic waveforms. Using continuous wavelet...

日本は世界で最も超音波による骨粗鬆症診断が盛んな国である．骨粗鬆症診断に関して，米国国立衛生研究所（National Institute of Health：NIH）は2000年のコンセンサス会議で「骨質（Bone Quality）」を定義した．この骨質とは骨のマクロ・ミクロな構造や，材料物性，マイクロクラックなどの骨の強度に関与する様々な要因の総称である．超音波法による骨診断は骨中を伝搬する音波の伝搬速度や伝搬減衰の情報を引き出してくれる．これらの情報は骨質，特に骨の弾性的性質にも依存している．このような視点のもとで，本稿では骨粗鬆症の初期症状が現れやすい海綿骨部位を取り上げる．特に，縦波超音波の興味深い伝搬現象とその骨構造（異方性）との関係について述べ，この現象を利用した新しい超音波骨評...

QUS parameters are closely related to the structural properties and elastic properties of bone, which can provide important information related to bone quality and bone strength. One should be very careful, however, that bone contains complicated structure from microscopic to macroscopic levels. For example, the cancellous bone inside the epiphysis...

A prototype for a bone-conducted ultrasonic hearing aid was developed for the profoundly deaf. Previous studies using bone-conducted ultrasonic hearing aid revealed intelligibility only with the use of acoustic media in transmitting language information. In this study, we investigated the effects of visual information (lip-reading information) on i...

Comparative study of longitudinal wave propagation in cancellous bone was performed. We simulated wave propagation with the finite-difference time-domain (FDTD) method using a threedimensional X-ray computer tomography (CT) model of an actual cancellous bone. We also experimentally measured the waves that propagated in an identical specimen under s...

This study showed that it is possible to transmit language information using bone-conducted ultrasound (BCU) in normal-hearing subjects. Our results suggest the possibility of a difference in speech recognition between BCU and air-conducted audible sound (ACAS). Ultrasound was audible when delivered by bone conduction. Some profoundly deaf subjects...

In order to understand the mechanism of two longitudinal wave propagation phenomena in the cancellous bone, we have tried to investigate the wave separation in the bone specimen by changing the main frequency of the longitudinal pulse wave. Here, we have used the specimens obtained from the end of bovine femur, which are covered by cartilage and su...

In cancellous bone, longitudinal waves often separate into fast and slow waves depending on the alignment of bone trabeculae in the propagation path. This interesting phenomenon becomes an effective tool for the diagnosis of osteoporosis because wave propagation behavior depends on the bone structure. Since the fast wave mainly propagates in trabec...

For diagnosing osteoporosis, ultrasonic systems are considered a powerful tool, because ultrasonic waves strongly depend on the elasticity and structure of cancellous bones. We have reported the separation of longitudinal waves into fast and slow waves, a phenomenon that is strongly connected to the alignment of bone trabeculae.In order to understa...

Cancellous bone is comprised of a complicated network of trabeculae and has strong anisotropy and inhomogeneity. In the cancellous bone, two types of longitudinal waves, fast and slow waves, are observed when the waves propagate parallel to the trabeculae direction. Paying attention to the wave front of observed waves, we have experimentally made c...

Longitudinal ultrasonic wave in cancellous bone separates into fast and slow waves depending on the bone structure. This phenomenon seems useful for the diagnosis of osteoporosis. In this study, we have investigated the influences of soft tissue (bone marrow) in the cancellous bone on the propagation of waves, in order to investigate the mechanism...

Aged or hearing-impaired people require better acoustical environments for higher QOL. Many methods of evaluating the quality of speech in acoustical environments have been developed. However, since they mainly focus on quality of speech in bad conditions (e.g. environments with huge noise or long reverberation), they are not suited for evaluations...

In cancellous bone, longitudinal waves often separate into fast and slow waves depending on the alignment of bone trabeculae. This interesting phenomenon becomes an effective tool for the diagnosis of osteoporosis because wave propagation behavior depends on the bone structure. We have, therefore, simulated wave propagation in such a complex medium...