Relationship between Piezoelectric Signal Generated in Cancellous Bone by Ultrasound Irradiation and Transmitted Ultrasound Signal

A piezoelectric finite-difference time-domain (PE-FDTD) method was used to simulate the piezoelectric signals generated in cancellous bone by ultrasound irradiation. The changes in the piezoelectric and ultrasound signals with the cancellous bone thickness were observed to clarify the relationship between these signals. In the ultrasound direction parallel to the strong trabecular orientation, the contributions of the fast and slow waves in the ultrasound signal to the piezoelectric signal were investigated. As a result, two waves could be identified in the piezoelectric signal. The amplitude of the former wave little varied with the cancellous bone thickness, but the amplitude of the later wave randomly varied although the variation was small. It was considered that the former wave corresponded to the local piezoelectric signal generated at the shallow depth of cancellous bone by majorly the fast wave and that the latter wave corresponded to the signal by majorly the slow wave.