Anisotropy of attenuation and backscatter in cancellous bone

Although bone sonometry is useful in the diagnosis of osteoporosis, the interactions between ultrasound and bone are not well understood yet. In order to investigate these processes, ultrasonic attenuation and backscatter in two orientations were measured in 43 human calcaneal specimens in vitro. In the mediolateral (ML) orientation, the ultrasound propagation direction is approximately perpendicular to the trabecular axes. In the anteroposterior (AP) orientation, a wide range of angles between the ultrasound propagation direction and trabecular axes is encountered. Average attenuation slope was 18% greater while average backscatter coefficient was 50% lower in the AP orientation compared with the ML orientation. These results support the idea that absorption is a greater component of attenuation than scattering in human calcaneal trabecular bone.