Publications by authors named "Yoshiki Nagatani"

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 by the two-wave phenomenon-based ultrasonic assessment of cancellous bone is introduced.

View Article and Find Full Text PDF
Article Synopsis
  • The study investigates how speech-modulated bone-conducted ultrasound (SM-BCU) can convey information about vowel duration, a crucial aspect of spoken language, particularly in distinguishing between words with different vowel lengths.
  • Eight Japanese-speaking participants performed a task to differentiate between "hato" (pigeon) and "haato" (heart) based on varying vowel durations presented through SM-BCU and traditional air-conducted sound.
  • Results showed that while the SM-BCU method required slightly longer vowel durations for accurate recognition compared to traditional sound (274.6 ms vs. 269.6 ms), both methods had a similar ability to convey vowel duration differences. *
View Article and Find Full Text PDF

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-dimensional acoustic simulation based on a finite-difference time-domain method from Bossy, Talmat, and Laugier [(2004).

View Article and Find Full Text PDF

Echolocating bats exhibit sophisticated sonar behaviors using ultrasounds with actively adjusted acoustic characteristics (e.g., frequency and time-frequency structure) depending on the situation.

View Article and Find Full Text PDF

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 using a wave transfer function with a phase rotation parameter was applied to received signals that have passed through bovine bone specimens with various bone volume to total volume (BV/TV) ratios in a simulation study, where the elastic finite-difference time-domain method is used and the ultrasound wave propagated parallel to the bone axes.

View Article and Find Full Text PDF

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 propagation in a trabecular bone sample in which a metallic pin has been inserted.

View Article and Find Full Text PDF

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 polynomial method were used to construct three-dimensional (3D) axial velocity models with a resolution of 40 μm.

View Article and Find Full Text PDF

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 in bone tissue. A metallic pin was inserted in bone tissue perpendicular to the transducer axis.

View Article and Find Full Text PDF

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 received signal is an important problem in the characterization of bone quality.

View Article and Find Full Text PDF

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 correlation coefficients between attenuation coefficient and frequency: 0.997 ± 0.

View Article and Find Full Text PDF

Invited for this month's cover is the group of Prof. Akihiko Tsuda from Kobe University and Kobe City Collage of Technology. The cover picture shows the alignment of a supramolecular nanofiber, composed of an anthracene derivative, while the Kobe University Symphony Orchestra was playing classical music.

View Article and Find Full Text PDF

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 nanomaterials, and is also interesting for investigation of unknown physical interactions between the molecules and audible sound vibrations. In this study, it was found that a supramolecular nanofiber, composed of an anthracene derivative AN, in an n-hexane solution aligned upon exposure to an audible sound wave at frequencies up to 1000 Hz, with quick responses to the sound and silence, and to amplitude and frequency changes of the sound wave.

View Article and Find Full Text PDF

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 instantaneous frequency (IF) of waveforms from multiple spectral channels.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

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 how the transition condition influenced the two-wave generation using three-dimensional X-ray CT images of an equine radius and a three-dimensional simulation technique.

View Article and Find Full Text PDF

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 the attenuation properties. Two methods are applied to simulated data that were generated based on experimentally acquired signals taken from a bovine specimen.

View Article and Find Full Text PDF

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 used to investigate the waves.

View Article and Find Full Text PDF
Article Synopsis
  • * A study examined how different durations of the vowel sound /a/ affected brain responses (N1m) in participants using various sound methods, including air-conducted sound and BCU.
  • * Results indicated that BCU modulated by speech has distinct effects on N1m compared to air-conducted speech, suggesting that the perception of speech-modulated BCU is mainly influenced by its ultrasonic properties rather than just the audible sounds.
View Article and Find Full Text PDF

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, the frequency of which is much lower (20-20,000 Hz). Here, we report on the design of a supramolecular nanofibre that in solution becomes preferentially aligned parallel to the propagation direction of audible sound.

View Article and Find Full Text PDF
Article Synopsis
  • A prototype bone-conducted ultrasonic hearing aid was created for profoundly deaf individuals, building on earlier studies that required acoustic media for intelligible sound transmission.
  • The study explored how visual cues, specifically lip-reading, affected sound perception in normal-hearing individuals using this type of hearing aid.
  • Results indicated that combining audio and visual information significantly enhanced the clarity of speech, supporting the potential effectiveness of using signal processing techniques to improve consonant understanding.
View Article and Find Full Text PDF
Article Synopsis
  • The study found that bone-conducted ultrasound (BCU) can effectively transmit language information to normal-hearing individuals and might lead to different speech recognition outcomes compared to air-conducted audible sound (ACAS).
  • The research highlights that both normal-hearing and some profoundly deaf subjects can differentiate BCU modulated by speech sounds, suggesting potential for creating a bone-conducted ultrasonic hearing aid (BCUHA).
  • Results indicated that while BCU achieved a correct response rate of about 75%, there were notable differences in speech intelligibility and confusion rates between BCU and ACAS, emphasizing the need for further research on BCU's perceptual qualities.
View Article and Find Full Text PDF

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 trabeculae, this wave is considered to reflect the structure of trabeculae.

View Article and Find Full Text PDF