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To verify the measurement of cortical bone thickness at the distal radius in vivo using an ultrasonic method. The method for estimating cortical bone thickness was derived from experiments with in vitro bovine specimens. Propagation time of echo waves and propagation time of slow waves were used for the estimation. The outside diameter of cortical bone and the cortical bone thickness at the distal 5.5 % site of radius were measured with the new ultrasonic bone measurement system, and the results were compared with X-ray pQCT clinical measurements. There was a high positive correlation (r: 0.76) between the cortical bone thickness measured by the new ultrasonic system and the X-ray pQCT results. We will be able to measure not only cancellous bone density but also cortical bone thickness in vivo using ultrasonic waves (without X-ray) safely and repeatedly.

Dual X-ray absorptiometry (DXA) is used to diagnose osteoporosis. On the other hand, quantitative ultrasound (QUS) is widely used to assess bone density as part of medical screening as it is relatively inexpensive and easy to perform. Current QUS devices do not share precise ultrasound-related parameters, such as frequency, waveform, beam pattern, transient response, definition of propagation time, definition of degree of attenuation, and precise measurement site, resulting in different measurements across models. The Japan Osteoporosis Society established a QUS Standardization Committee in 2007 to investigate standardization of speed of sound (SOS) and broadband ultrasonic attenuation (BUA) measurements to resolve this issue. The committee came up with a formula to convert SOS and BUA values yielded by each model available in Japan. This has made it possible to convert QUS measurements from different models into standardized values, greatly improving the effectiveness of QUS measurements.

A reference database for trabecular bone density, cortical thickness, and elastic modulus of trabecular bone for a novel ultrasonic bone densitometry system (LD-100) based on two longitudinal waves (fast and slow) was determined over a wide age range in a normal Japanese population. A novel ultrasonic bone densitometry system (LD-100 system) was applied to create a reference database for trabecular bone density (TBD), cortical thickness (CoTh), and elastic modulus of trabecular bone (EMTb) for this device over a wide age range in a normal Japanese population. In a comparative study between LD-100 and peripheral quantitative computed tomography (pQCT) systems, 52 individuals were examined by both systems at the same radius simultaneously. To create a reference database, a total of 2,380 healthy subjects (1,179 men, 1,201 women), ages 18–99 years, were examined using the LD-100 system. Highly significant correlations between the LD-100 and pQCT systems were found in TBD (r = 0.877, p

Two longitudinal transmitted waves, fast and slow waves, were observed by employing a new quantitative ultrasound (QUS) method. The trabecular bone measurements generated by this method reflect three-dimensional structural information, and the new QUS parameters were able to identify vertebral fractures. The aims were to identify new quantitative ultrasound (QUS) parameters that based on new QUS method reflecting not only bone volume but also the microstructures of trabecular bone ex vivo and to observe how much they predict fracture risk in vivo. Ex vivo measurement: Three human femoral heads were used for the experiment. Attenuation of the slow wave, attenuation of the fast wave, speed of the slow wave, speed of the fast wave (SOFW), bone mass density of trabecular bone, and elastic modulus of the trabecular bone (EMTb) of each specimen were obtained using a new QUS method and compared with three-dimensional structural parameters measured by micro-computed tomography. In vivo measurement: Eighty-nine volunteers were enrolled, and the bone status in the distal radius was measured using a new QUS method. These parameters were compared with data evaluated by peripheral quantitative computed tomography and dual X-ray absorptiometry. Ex vivo measurement: SOFW and EMTb showed correlations with the parameter of trabecular anisotropy. In vivo measurement: The new QUS parameters were able to identify vertebral fractures. The newly developed QUS technique reflects the three-dimensional structure and is a promising method to evaluate fracture risk.

Ultrasonic waves in cancellous bone change dramatically depending on its structural complexity. One good example is the separation of an ultrasonic longitudinal wave into fast and slow waves during propagation. In this study, we examined fast wave propagation in cancellous bone obtained from the head of the bovine femur, taking the bone structure into consideration. We investigated the wave propagation perpendicular to the bone axis and found the two-wave phenomenon. By rotating the cylindrical cancellous bone specimen, changes in the fast wave speed due to the rotation angle then were observed. In addition to the ultrasonic evaluation, the structural anisotropy of each specimen was measured by X-ray micro-computed tomography (CT). From the CT images, we obtained the mean intercept length (MIL), degree of anisotropy (DA), and angle of insonification relative to the trabecular orientation. The ultrasonic and CT results showed that the fast wave speed was dependent on the structural anisotropy, especially on the trabecular orientation and length. The fast wave speeds always were higher for propagation parallel to the trabecular orientation. In addition, there was a strong correlation between the DA and the ratio between maximum and minimum speeds (V(max)/V(min)) (R(2) = 0.63).

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 by the finite-difference time-domain (FDTD) method, using a three-dimensional X-ray computer tomography (CT) model of an actual cancellous bone. In this simulation, experimentally observed acoustic constants of the cortical bone were adopted. As a result, the generation of fast and slow waves was confirmed. The speed of fast waves and the amplitude of slow waves showed good correlations with the bone volume fraction. The simulated results were also compared with the experimental results obtained from the identical cancellous bone.

超音波による骨の評価は踵を測定部位とすることが多く, その指標の一つとして音速 (SOS) が用いられる. 物質の音速は一般に温度の影響を受けるが, 人体の場合は温度は安定していると認識されていた. 踵は末端部であり冬季では体温より温度が低くなり音速に影響する. この現象は超音波骨評価装置が普及するにつれて知られるようになったが, これまでの研究では踵の音速と温度の相関を見るか, 脂肪などの一部の組成の温度特性のみの測定であり, 系統立てて関連付けた研究はなかった. 踵を構成する各生体組織である皮質骨, 骨髄, 海綿骨, 表皮, 筋肉, 脂肪および皮下脂肪の温度特性をウシから摘出したサンプルを用いて測定した. その結果, 皮質骨, 骨髄, 脂肪の温度係数が大きいのに対し, 筋肉や表皮の温度係数は小さかった. 皮質骨と骨髄はほぼ同じ温度係数を示したが, 海綿骨の温度係数はその半分程度であった. 各生体組織の厚さと温度係数を用いて踵の音速を計算し, その温度特性を推定した. 21名の女性の踵の音速の温度係数を測定した結果は推定結果と良い一致を得た.

Making use of the RF magnetron sputtering technique, we have succeeded in fabricating ZnO films where c -axis of crystallites are unidirectionally aligned in the plane, without the mechanism of epitaxy. The alignment of c -axis in the plane was then carefully investigated by the X-ray pole figure analysis and atomic force microscope measurements. From these results, we have revealed the effect of substrate position during sputtering on the c -axis alignment in the plane. We have also pointed out the important effect of the oxygen ions in the RF plasma on the (1 1 2¯ 0) texture formation.

Ultrasonic wave properties (attenuation and velocity) in the particle compounded agarose gels have been experimentally studied in the range from 1 to 30 MHz. The particles used were talc, glass beads and graphite. The effects of size and volume concentration of particles were clearly observed as changes of ultrasonic wave properties. Applying the Urick's theory for viscous liquid suspensions, the specific curves of velocity in the gels were observed as a function of a beta, where a is the radius of the particles and beta is described by angular frequency omega, density rho and fluid viscosity eta. This indicates that the particle behavior in the gels seems to be similar with that in the viscous fluid. The estimated eta in the gels was higher than that of the free water, showing the high viscosity in the gels.

In the original version of the article, the third author name was incorrectly published. The correct name is Kosei Yoh.

A distinctive irregularity in the frequency response of a piezoelectric polymer film hydrophone, which is not predicted by the use of conventional theory, has been observed. It was confirmed in a previous study [Y. Nakamura and T. Otani, Jpn. J. Appl. Phys. Suppl. 31‐1 31, 266–268 (1992)] that the irregularity can be attributed to the radial resonance of a surface wave induced by the incident pressure on the hydrophone’s backing material. To estimate theoretically the frequency response of the hydrophone, the transient acoustic field on the receiving surface of the hydrophone was studied by time‐domain analysis. The field is theoretically described in the time domain as the superposition of an incident wave, a reflected plane wave, a diffracted edge wave, and a leaky elastic wave that originates from a surface wave propagating along the radius on the hydrophone’s backing material. The validity of the theoretical analysis of the acoustic field on receiving surface is verified by experimental observations. ...

The influence of cancellous bone microstructure on the ultrasonic wave propagation of fast and slow waves was experimentally investigated. Four spherical cancellous bone specimens extracted from two bovine femora were prepared for the estimation of acoustical and structural anisotropies of cancellous bone. In vitro measurements were performed using a PVDF transducer (excited by a single sinusoidal wave at 1 MHz) by rotating the spherical specimens. In addition, the mean intercept length (MIL) and bone volume fraction (BV/TV) were estimated by X-ray micro-computed tomography. Separation of the fast and slow waves was clearly observed in two specimens. The fast wave speed was strongly dependent on the wave propagation direction, with the maximum speed along the main trabecular direction. The fast wave speed increased with the MIL. The slow wave speed, however, was almost constant. The fast wave speeds were statistically higher, and their amplitudes were statistically lower in the case of wave separation than in that of wave overlap.

The aim was to evaluate a new ultrasound device in a young adult population and to assess its reproducibility via comparison to DXA measurements and geometrical measurements from high-resolution radiographs. Ninety-three subjects aged between 20 and 51 years were recruited and divided into four groups according to their gender and physical activity status: 22 male athletes, 19 male controls, 21 female athletes, and 31 female controls. Ultrasonic measurements were assessed by the prototype LD-100 (Oyo Electric Co., Kyoto, Japan) on the dominant distal radius. Attenuation in the radius (dB), cortical bone thickness (mm), radius thickness (mm), mass density of cancellous bone (mg/cm(3)), and elasticity (GPa) of cancellous bone were obtained. BMD was measured by DXA at the dominant distal radius. Radius images were obtained with a direct high-resolution digital X-ray device (BMA, D(3)A Medical Systems), and radius and cortical thicknesses were estimated using a specific software (ImageJ, Bethesda, USA), in an area site-matched with LD-100. There was a significant positive correlation between site-matched BMD measurement and LD-100 parameters (p0.004), X-ray radius thickness, and LD-100 parameters except elasticity (p0.05, r0.32), X-ray cortical thickness and LD-100 attenuation and cortical thickness (p0.01). A significantly higher attenuation, cortical and radius thicknesses were found in athletes compared to controls (p0.05). The radius thickness measured on radiographs was significantly higher in athletes versus controls in both sexes, and cortical thickness was significantly higher in male athletes versus controls. These data suggest a positive influence of physical activity on bone cortical measurements. This study also confirmed the particular interest of bone assessment by ultrasound.

It is known that the ultrasonic longitudinal wave which passed through the cancellous bone is separated into two waves, the fast and the slow waves. The fast wave, especially, reflects the bone structure because it mostly passes though the trabeculae. Then, we have focused on the fast wave speed in the cancellous bone obtained from the head of bovine femur, taking the bone structure into consideration. In the ultrasonic measurement, the changes in the fast wave speed due to the trabecular orientation have been observed with rotating the cylindrical cancellous bone specimen. In addition to the ultrasonic measurements, structural anisotropy of each specimen was measured by X-ray micro CT (Hitachi). From CT images, we obtained the mean intercept length (MIL), degree of anisotropy (DA) and an angle thetas, which is the angle of insonification relative to trabecular orientation. The ultrasonic and CT results showed that the fast wave was strongly affected by the structural anisotropy, especially on the trabecular orientation and length.

This paper reports the fabrication and characterization of ZnO piezoelectric thin films in which the crystallite c-axis is unidirectionally aligned in the plane. The films were deposited by a conventional radio frequency (RF) magnetron sputtering apparatus without epitaxy. We have measured reflection coefficient S/sub 11/ of the ZnO film/glass substrate composite shear mode resonator and confirmed that the resonator excites shear wave only in the very high frequency to ultra high frequency ranges (VHF-UHF). The crystallites c-axis orientation and alignment were determined by X-ray diffraction (XRD) patterns, /spl phi/-scan pole figure analysis, /spl omega/-scan rocking curves, and atomic force microscope (AFM) measurement. The transduction of the shear wave showed good agreement with properties of the crystallite alignment in the film.

Using a conventional RF magnetron sputtering system, we have successfully obtained ZnO films in which the crystallites' c-axis is unidirectionally aligned in the substrate plane without an epitaxial technique. These are almost pure (112~0) textured films. The alignment of the crystallite c-axis in the plane was then carefully investigated by X-ray pole figure analysis and AFM. We found that the crystallites of the film were oriented randomly at the anode center and unidirectionally near the edge of the anode. Using the ZnO film, we have fabricated an ultrasonic transducer which consists of a metal electrode/(112~0) textured ZnO film/Al electrode film structure. The transducer clearly excited a shear wave without any longitudinal waves. These results indicate the wide application of this film in shear-mode resonators and SH-type SAW devices on any substrates.

A Brillouin scattering technique has been applied to investigate the ultra-drawing process of polypropylene films. The gradual elastic changes during the drawing process showed the appearance of anisotropy and birefringence of the sample. Devising the optical geometry of Brillouin scattering measurement, continuous changes of the birefringence during ultra-drawing were clearly observed. These data were compared with the data obtained using a polarizing microscope, which were acquired at specific points of the drawing process.

The ultrasonic longitudinal wave in the cancellous bone is separated into two waves, fast and slow waves [1]. In this study, the relationship between the fast wave speed and the cancellous bone structure is experimentally investigated. A conventional ultrasonic pulse measurement was performed using a PVDF focus transmitter (Custom made, Toray) and a self‐made PVDF receiver. Cylindrical specimens of cancellous bone were taken from the head of bovine femur in the distal part, along the three orthogonal directions. The distribution of fast wave speed was obtained by changing the measurement position along the cylindrical axis. The anisotropy of speed was also investigated by rotating the specimens. The structural parameters of each specimen were also measured by X‐ray micro CT (MCT‐12505MF, Hitachi), which gave us the trabecular length and alignment from MIL (mean intercept length) parameters through TRI/3D‐Bon software (Ratoc). We found that the fast wave showed large distribution and strong anisotropy depending on the measurement positions and wave propagation directions in the specimens. The fast wave showed the maximum speed in case of wave propagation along the load direction. Reference [1] A. Hosokawa and T. Otani, J. Acoust. Soc. Am., 101, 558 (1997).

Cancellous bone is comprised of a connected network of trabeculae and is considered as an inhomogeneous and anisotropic acoustic medium. The fast and slow longitudinal waves are clearly observed when the ultrasonic wave propagates parallel to the direction of the trabeculae. The propagation speed of the fast wave increases with bone density and that of the slow wave is almost constant. The fast wave amplitude increases proportionally and the slow wave amplitude decreases inversely with bone density. Human in vitro femoral head was sectioned to 10‐mm‐thick slices perpendicularly to the femoral cervical axis. These cancellous bone samples were subjected to the ultrasonic measurement system LD‐100 using a narrow focused beam. The propagation speed and the amplitude of the transmitted wave both for the fast and slow waves were measured at 1‐mm intervals. The local bone density corresponding to the measured points was obtained using a microfocus x‐ray CT system. Experimental results show that the propagation speeds and amplitudes for the fast and slow waves are characterized not only by the local bone density, but also by the local trabecular structure.

The distribution of longitudinal wave velocities and longitudinal moduli in a bovine femoral cortical bone was experimentally investigated. In all parts of the long cylindrical bone, the velocities and longitudinal moduli in the axial direction were the highest. In the anterior (A) part, the velocities in the axial direction were high and almost constant, whereas the velocities in the proximal postero medial (PM) and distal postero lateral (PL) parts markedly decreased. Classifying the cortical bone into three structures (plexiform, Haversian, and porotic), we clarify the velocity distributions in the bone with discussion from an anatomical point of view.

Using a conventional RF magnetron sputtering system, we have obtained two types of ZnO films on various kinds of substrate. One is a film with the c-axes of crystallites unidirectionally aligned in the substrate plane {(112̄0) textured film}. The other is a film with c-axes parallel and perpendicular to the plane (mixed texture film). The former is expected to realize a shear wave transducer on the surfaces of various materials. The alignment of c-axes of crystallites in the plane was then carefully investigated by the X-ray pole figure analysis. The elastic anisotropy in the film has been successfully measured by the Brillouin scattering method. The (112̄0) textured film did not excite the elastic waves; however, comparatively strong shear waves were actually excited by the mixed texture film.

Reflection-induced ΘA Brillouin scattering (RIΘA) is introduced to investigate the opto-acoustic anisotropy of uniaxially stretched polyvinylidene fluoride (PVDF) films (0.04 mm in thickness). Although the films are not perfectly transparent, their elastic and optical anisotropy could be investigated nondestructively. The optical anisotropy, which is observed as birefringence, showed a clear decrease near the Curie temperature (T c).

The effect of tensile stress on the hypersonic wave velocities of polymer films was investigated using a Brillouin scattering method. From the real-time measurements during the tensile test, an interesting behavior of the longitudinal wave velocity has been observed. By comparing the velocity profile with the stress-strain curve, velocity changes indicate that the small scale deformation of the film propagates from the edge to the center and gradually spreads. These results point out the possibility of the Brillouin scattering method as a useful tool for nondestructive and real-time measurement of the stress and deformation in the sample.

Acoustic scattering and reflection phenomena at the surface of marine sediment models were visualized by the shadowgraph method with an impulse source realized by a small spark gap. Water saturated glass beads were used as a sediment model. Lateral wave was clearly observed for fine sediments (small grain size compared with wavelength). Scattered waves and multiple reflected waves were observed for coarse sediments (larger or equivalent grain size compared with wavelength).

Short impulsive acoustic waves are widely applied today to acoustical imaging systems for medical diagnosis, nondestructive testing and underwater geophysical survey to obtain a better range resolution. The waveform of short impulsive waves are considerably deformed according to the distance from the acoustic source and the axial angle, and consequently the range resolution and the azimuth resolution are incompatible. The transient acoustic field radiated by a piston source and the phenomenon of waveform deformation of the transient acoustic field are discussed. It is shown that the directional characteristics of a transient wave depend on the acceleration waveform as well as on the configuration and dimensions of the radiator surfaces and that the directivity pattern is essentially dependent on the reciprocal of sin θ.

Attenuation and sound velocity in particle compounded agar were measured by an ultrasonic wave transmission technique at frequencies ranging from 1 MHz to 8 MHz. The observed values were discussed using Urick's theory for viscous suspensions. The measured values of attenuation and sound velocity were in good agreement with the calculated values using Urick's theory up to a particle concentration of 10%. This means that Urick's theory can be applied not only to suspensions, but also to particle compounded gels. Furthermore, from the investigation of the experimental results obtained using this theory, it was clarified that the attenuation depends on the particle density. In particular, it should be noted that n depends on the particle diameter (the attenuation α can be expressed with the equation α= α0 f n, where α0 and n are constants and f is frequency). All measured and calculated results suggested that the acoustic properties in these kinds of particle compounded gels could be estimated theoretically.

Wave properties (wave velocity and attenuation) in epoxy adhesive layers during cure were investigated. Longitudinal and shear wave properties in the GHz region were measured by the Brillouin scattering technique using 90°A-scattering geometry. The longitudinal and shear wave properties showed similar changes during cure. Compared with the ultrasonic wave properties in the MHz region, a clear frequency dispersion could be seen during cure, in the glass transition region. It is supposed that this dispersion results from a strong α relaxation. Longitudinal modulus and shear modulus were also obtained from the longitudinal and shear wave velocities. The longitudinal modulus was always proportional to the shear modulus during the entire curing process.

Ultrasonic wave propagation in water-saturated bovine cancellous (spongy) bone has been experimentally studied in vitro by a pulse transmission technique. The propagation of fast and slow longitudinal waves in bovine cancellous bone [rf:1] is examined in relation to porosity using Biot's and Wyllie's equations to estimate the measured speeds versus porosity. In the high porosity range, the trabecular structure influences the propagation of the fast and slow waves in cancellous bone.

The construction of piezoelectric polymer film hydrophones has been studied in order to suppress irregularities in hydrophone frequency response and directivity characteristics caused by the formation of induced surface waves on the backing material. A polyvinylidene fluoride (PVDF) hydrophone having a cylindrical baking material rounded at its edge is shown to have flat frequency response in the range of 100 kHz to 10 MHz and to have good directivity in agreement with piston motion theory.

Sound sources using electric discharge to radiate a short impulsive spherical sound are described. Experimental results show that a very narrow space between two electrodes provides a spherical wave front and can be regarded as a point source. Radiated waveforms depend on the discharge parameters, and simple sound waveforms such as one period of sine or squared cosine are approximately obtained. Impulsive sounds generated by electric breakdown (electric discharge) at a focus of high intensity laser beam are also investigated.