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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).

An ultrasonic wave transmitted through an in vitro human cancellous bone was experimentally investigated. An osteoporotic cancellous bone specimen was obtained from an in vitro femoral head. A narrow ultrasonic beam was scanned on the specimen surface over an area of 30×30 mm2 and the transmitted ultrasonic wave was obtained at an interval of 1 mm. Local bone densities corresponding to measurement points using the ultrasonic beam were obtained using a microfocus X-ray computed tomography system. Transmitted slow wave signals were detected at all measurements points; however, the measurable area of a fast wave was greatly reduced and limited because of the osteoporotic low-density specimen. The propagation speed of a slow wave was almost independent of bone density. The propagation speed of the fast wave and the amplitudes of the fast and slow waves considerably depended on bone density. The obtained results imply that the scattered values of the propagation speed of the fast wave and the amplitudes of the fast and slow waves reflect the ultrasonic characteristics of the cancellous bone, which depend on both the bone density and the trabecular macro- and micro-structures.

Osteoporosis is a disease characterized by decreasing bone density, and is assessed by the bone mass density of cancellous bone. An X-ray method is widely used for noninvasive measurement of bone mass density [mg/cm3]. An ultrasonic method has the potential to evaluate the elastic properties, however measured ultrasonic parameters are the slope of frequency dependent attenuation (BUA [dB/MHz]) and the speed of sound (SOS [m/s]), not the bone mass density [mg/cm3]. In previous study, two longitudinal waves, the fast and slow waves, were observed in cancellous bone. In this study, the propagation path through cancellous bone is modeled to specify the causality between ultrasonic wave parameters and bone density. Then bone density and bone elasticity are quantitatively formulated. A novel ultrasonic bone densitometry, prototype LD-100, have been developed. The bone density [mg/cm3] and the bone elasticity [GPa] are evaluated by ultrasonic parameters based on the fast and slow waves in cancellous bone using a modeling of ultrasonic wave propagation path.

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.

Urick's theory of viscous liquid suspensions has been applied to investigate the ultrasonic wave properties in small-particle dispersed agarose gels. Based on the idea of apparent shear viscosity of the gel medium, the theoretically estimated velocity showed good agreement with the experimental data in the MHz range. The characteristic velocity decrease in viscous suspensions, due to the increase of volume concentration or density of particles, was also observed clearly in the particle-dispersed gels. This phenomenon becomes clearer in the region aβ7, where a is the radius of the particles and β is described by angular frequency ω, density ρ and fluid viscosity η.

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.

The isothermal curing process of thin epoxy adhesive layers (mixture of a bisphenol A-based epoxy prepolymer and an aliphatic diamine curing agent) has been investigated. The Brillouin scattering technique with 90 degrees A scattering geometry enables simultaneous measurements of longitudinal and shear wave properties in the GHz range. Observed longitudinal and shear wave velocities showed similar changes during cure. They rapidly increased and gradually became constant, reflecting the elastic changes of the epoxy layer. The final velocities, however, clearly depended on the curing temperature. Taking the glass transition process of epoxy resins into consideration, these curing behaviors in thin layers are discussed.

A novel ultrasonic bone densitometer, prototype LD-100, has been developed to overcome problems inherent in an ultrasonic method and to obtain bone mass density in the unit of mg/cm3 and bone elasticity in the unit of GPa with a spatial resolution comparable to that of the peripheral quantitative computed tomography (pQCT) system. Bone mass density and bone elasticity are evaluated using ultrasonic parameters based on fast and slow waves in cancellous bone using a modeling of ultrasonic wave propagation path. A good reproducibility of measured values and two-dimensional (2D) imaging of bone density and bone quality are realized by two scannings with an automatic measurement algorithm.

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. ...

Sound speed and absorption constant of saturated marine sediment samples of Setouchi (the inland sea of Japan) and Hekinan Coast were measured by use of a tube method in a frequency range from 6.6 kHz to 11.0 kHz. Grain diameter distribution, porosity and density of sediments were also measured for each sample. And sound speed and absorption constant of the same sediment samples were measured in a frequency range from 40 kHz to 250 kHz by free sound field method. The sound speed and the attenuation coefficient were theoretically estimated based on the generalized Biot's theory on the acoustic wave propagation through porous media. A validity of the Biot's theory to apply the saturated marine sediment is confirmed by a comparison between the theoretical estimation and experimental measurements.

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.

The ultrasonic wave propagation of fast and slow waves was investigated in vitro in 35 cubic cancellous bone specimens extracted from human femoral heads. Measurements were performed in three orthogonal directions using home-made PVDF transducers excited by a single sinusoidal wave at 1 MHz. The apparent density of the specimens was measured. Two separated fast and slow waves were clearly observed in 16 specimens, mainly in the main load direction. The waveforms and the sound speeds of fast and slow waves were similar to the reported data in bovine bone. The group of specimens in which the two waves were observed did not exhibit statistically higher apparent density than the rest of the specimens, but did exhibit statistically higher acoustic anisotropy ratio. The speeds in the main load direction were higher than those in the other direction. The fast and slow wave speeds were in good agreement with Biot's model, showing an increase with bone volume fraction (BV/TV). The ratio of peak amplitudes of the fast and slow waves nonlinearly increased as a function of BV/TV. These results open interesting perspective for acoustic assessment of cancellous bone micro-architecture and especially anisotropy that might lead to an improved assessment of bone strength.

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.

Ultrasonic transmitted waves were obtained in an in vitro swine distal ulna specimen, which mimics a human distal radius, that consists of interconnected cortical bone and cancellous bone. The transmitted waveforms appeared similar to the fast waves, slow waves, and overlapping fast and slow waves measured in the specimen after removing the surface cortical bone (only cancellous bone). In addition, the circumferential waves in the cortical bone and water did not affect the fast and slow waves. This suggests that the fast-and-slow-wave phenomenon can be observed in an in vivo human distal radius.

The detailed spatial distributions of longitudinal ultrasonic velocity in cortical bone specimens obtained from three bovine femoral diaphysis were experimentally investigated using a pulse-echo system. The relationship between velocity, density, bone mineral density (BMD) and microstructure was investigated. Velocity was found to vary as a function of the direction of propagation and the location of the measured specimens in the bone diaphysis. A significant correlation was found between density and velocity, and between density and BMD. In some parts with plexiform structure, clear variations in velocity anisotropy were found despite no significant difference in density, BMD and microstructure.

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.

Ultrasonic measurements of bone status or bone mass density are generally performed using ultrasonic parameters consisting of the slope of frequency-dependent attenuation (or broadband ultrasound attenuation: BUA) and the speed of sound (SOS). Many results of in vitro laboratory measurements and in vivo clinical trials have shown the ultrasonic parameters, BUA and SOS correlate significantly with the bone mass density measured by X-ray method. However, there exists some problem inherent in the ultrasonic method on the reproducibility and the uncertainty of measured ultrasonic parameters. The ultrasonic properties of cancellous bone have been experimentally and theoretically studied by author's group to reveal problems inherent in the ultrasonic method. According to experimental and theoretical studies, two longitudinal waves, fast wave and slow wave are clearly observed. The propagation speed of the fast wave increases with the bone density and that of the slow wave decreases very slightly with the bone density. Whereas the attenuation constant of the fast wave is much higher than that of the slow wave and is almost independent of the bone density, but in contrast, the attenuation constant of the slow wave increases considerably with the bone density. Experimental results on transmitted ultrasonic wave through cancellous bone show that the amplitude of the slow wave decreases with the bone density and the amplitude of the fast wave, on the contrary, increases with the bone density. This dependence of the fast wave amplitude on the bone density can not be explained by the attenuation constant. The ultrasonic wave propagation path through cancellous bone is modelized to clarify the propagation phenomenon and to specify the causality between ultrasonic wave parameters and the bone density. The bone density is quantitatively formulated based on the modelization as a function of the amplitude and the propagation speed of the fast wave.

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.

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 circumferential waves on the fast and slow waves. When the diameters of the focused transducers were small, the appearance of the circumferential wave around the cortical bone became late, and it could avoid one of the influences of the circumferential waves.

The acoustic properties of bovine cancellous (spongy) bone have been experimentally studied in vitro by the pulse transmission technique. Fast and slow longitudinal waves have been clearly identified when the acoustic wave propagates parallel to the direction of the trabeculae. Propagation speeds and attenuation of the fast and slow waves were observed in the frequency range of 0.5–5 MHz. Theoretical discussion is given to Biot’s theory and the propagation of sound waves in fluid-saturated porous media.

We have tried in vivo imaging of the distal forearm bone using ultrasonic echo waves. The obtained ultrasonic echo images were compared with X-ray computed tomography (CT) images. In the case of vertical incidence of an ultrasonic wave to the cortical bone surface, not only the outer and inner boundaries of the near side of the cortical bone but also the inner and outer boundaries of the far side of the cortical bone were identified. The thicknesses of the cortical bone and cancellous bone calculated using the echo waves approximately agreed with those determined from X-ray CT images.

Longitudinal wave in cancellous bone separates into fast and slow waves depending on the alignment of trabeculae. Here, the fast wave mainly propagates in trabeculae, whereas slow wave propagates in the soft tissue (bone marrow). Because these two waves usually overlap, the evaluation of each wave has still remained difficult. In this study, then, we have tried to evaluate the wave properties (attenuation and velocity), making use of the plane wave in an acoustic tube. 3-D image of the bone specimen was obtained by X-ray micro CT. In an acoustic tube, a cancellous bone specimen was set between home-made PVDF transducers. A function generator delivered a single sinusoidal signal in the range of 0.5 to 1.5 MHz to the transmitter. By filing a part of bone specimen away, we have tried to obtain the attenuation and velocity of the specimen. The two wave phenomenon clearly occurred in our specimen. In some trabecular bones of big animals, the wave separated perfectly. We have then tried to obtain ultrasonic pro...

The effect of decreasing bone density (a symptom of osteoporosis) is greater for cancellous bone than for dense cortical bone, because cancellous bone is metabolically more active. Therefore, the bone density or bone mineral density of cancellous bone is generally used to estimate the onset of osteoporosis. Elasticity or elastic constant is a fundamental mechanical parameter and is directly related to the mechanical strength of bone. Accordingly, elasticity is a preferable parameter for assessing fracture risk. A novel ultrasonic bone densitometer LD-100 has been developed to determine the mass density and elasticity of cancellous bone with a spatial resolution comparable to that of peripheral quantitative computed tomography. Bone density and bone elasticity are evaluated using ultrasonic parameters based on fast and slow waves in cancellous bone by modeling the ultrasonic wave propagation path. Elasticity is deduced from the measured bone density and the propagation speed of the fast wave. Thus, the elasticity of cancellous bone is approximately expressed by a cubic equation of bone density.

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).

Effect of decreasing bone density (a symptom of osteoporosis) is greater for cancellous bone than for dense cortical bone, because cancellous bone is metabolically more active. Therefore, bone density or bone mineral density at cancellous bone is generally used to estimate the onset of osteoporosis. Elasticity or elastic constant is one of fundamental mechanical parameters and directly related to the mechanical strength of bone. Accordingly, elasticity is a preferable parameter to assess the fracture risk. A novel ultrasonic bone densitometer LD‐100 has been developed to obtain mass density and elasticity of cancellous bone with a spatial resolution comparable to that of the peripheral quantitative computed tomography system. Bone mass density and bone elasticity are evaluated using ultrasonic parameters based on fast and slow waves in cancellous bone using a modeling of ultrasonic wave propagation path. Elasticity is deduced from measured bone mass density and propagation speed of fast wave. Thus, elasti...

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.

Cancellous bone (spongy bone) is comprised of a porous network of numerous trabecular elements with soft tissue in the pore space. The effect of decreasing bone density, namely a symptom of osteoporosis, is greater for cancellous bone than for dense cortical bone (compact bone). Two longitudinal waves, the fast and slow waves, are clearly observed in cancellous bone, which correspond to ‘‘waves of the first and second kinds’’ as predicted by Biot’s theory. According to experimental and theoretical studies, the propagation speed of the fast wave increases with bone density and that of the slow wave is almost constant. Experimental results show that the fast wave amplitude increases proportionally and the slow wave amplitude decreases inversely with bone density. However, the attenuation constant of the fast wave is almost independent of bone density and the attenuation constant of the slow wave increases with bone density. The in vivo ultrasonic wave propagation path is composed of soft tissue, cortical bo...

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.

In previous studies, two longitudinal waves, the fast and slow waves, were observed in cancellous bone. The propagation speed of the fast wave increases with bone density and that of the slow wave remains almost constant. The attenuation constant of the fast wave is much higher than that of the slow wave and is independent of bone density, but the attenuation constant of the slow wave increases with bone density. In the present study, experimental results on ultrasonic waves transmitted through cancellous bone show that the fast wave amplitude increases proportionally and the slow wave amplitude decreases inversely with bone density. The dependence of the fast wave amplitude on bone density cannot be explained by the attenuation constant. The ultrasonic wave propagation path through cancellous bone is modeled to specify the causality between ultrasonic wave parameters and bone density. Then bone density and bone elasticity are quantitatively formulated.

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.