Two-wave phenomenon in cancellous bone has been reported by several investigators. Making use of this phenomenon, a new QUS device has been introduced to evaluate the radius in vivo. We have also reported that two waves reflect not only bone mass but also the complex bone structure of cancellous bone. We then propose a new simple imaging technique based on the two-wave phenomenon for investigating the anisotropic structure. Cylindrical specimens of cancellous bone were obtained from a bovine femur. Using a conventional ultrasound pulse technique, we rotated the receiver around the specimen to investigate the ultrasonic fields after the propagation in the specimen. In addition, structure of the specimen was estimated by using the X-ray micro CT data. The ultrasonic propagation image clearly showed the effect of the bone structure. We can find "fast" wave showing "apparent refraction". The propagation image is simple and convenient for easy understanding of the anisotropy. The image may become a user-friendly tool for the future in vivo assessment.
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