P5A-2 An Experimental Study on the Ultrasonic Wave Propagation and Structural Anisotropy in Bovine Cancellous Bone

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.