2D Simulation of the Axial Transmission Technique on a Cortical Bone Plate

Abstract

In recent years, quantitative ultrasound (QUS) has demonstrated its ability to detect bone fragility as well as bone absorptiometry. The axial transmission technique has been developed to study propagation along the cortical shell of long bones. In such a technique, both the emitter and the receiver are in contact with the skin, placed on a same side of the skeletal site. The first arriving signal (FAS) at the receiver is used to derive an apparent SOS. The FAS has been presented,, as a wave emitted from the surface at the longitudinal critical angle. It has been identified by Camus et al., in the case of an interface between two semi-infinite media, as the lateral wave propagating along the interface with the longitudinal bulk velocity of the solid. Nevertheless, the type of propagation occurring along bone specimens, of finite thickness and curved geometry, has not been clearly elucidated yet. Recently, it has been shown experimentally that the apparent SOS of the FAS is dependent on the thickness of the studied sample. As the cortical thickness changes with aging and osteoporosis, and has been shown to be a risk factor for fracture, it is critical to elucidate the relationship between the apparent SOS and the cortical thickness. Using 2-D numerical simulations of 1MHz ultrasound propagation, we will focused on the apparent SOS for bone plates in water, in order to study the relationship between apparent SOS and cortical thickness. Attention will be paid to the accuracy of the measurement and to the impact of the signal processing techniques on measured SOS values.