“…Critical-angle reflectometry has been used to measure the speeds of sound in bone and therefore to calculate the elastic properties of that material [14][15][16]. Antich et al [15] and Mehta et al [16] demonstrated experimentally that mode conversion occurs when a wave impinges on the interface between materials of different acoustic impedance (water and bone) at an oblique angle of incidence. PZ-Flex (Weidlinger Associates), a finite element modeling package, has been used to model in two dimensions a cross sectional of the human thigh, consisting of muscle, cortical femoral bone, and bone marrow [17].…”