Numerical investigation of ultrasound reflection properties in cancellous bone

Abstract

Bone is composed of two components of cancellous and cortical bones, and cancellous bone is generally surrounded by cortical bone. Therefore, ultrasound waves propagating in bone can reflect at the boundary between cancellous and cortical bones. In this study, the ultrasound reflection properties in cancellous bone were numerically simulated using a finite-difference time-domain (FDTD) method with microcomputed tomographic (μCT) models of the bone. From the simulated results, it was investigated how the ultrasound waves propagating in cancellous bone could reflect at the boundary. The reflected waveform at normal incidence to the boundary was calculated using the numerical model comprised of two layers of cancellous and cortical bones, and only the reflection properties were derived by subtracting the waveform calculated using the model adopting the absorbing boundary condition instead of the cortical bone layer. In the case of the strong trabecular orientation parallel to the ultrasound propagation, the reflections of both fast and slow longitudinal waves could be observed.