Axial transmission of 1 MHz ultrasonic waves on thin cortical bone plates: a simulation study

Ultrasonic wave propagation involved in axial transmission technique is investigated in the case of an elastic bone plate, by means of 2D simulation. We focus our interest on the apparent speed of sound (SOS) of the first arriving signal (FAS). Its dependence on the thickness of the plate is discussed and compared to previous work. Different time criteria are used to derive the apparent SOS of the FAS as a function of source-receiver distance. For thick plates (thickness>λ_bone, longitudinal wavelength in bone), and for a limited range of source-receiver distances, the FAS corresponds to the lateral wave. For plate thickness less than λ _bone, some plate modes contribute to the FAS, and the apparent SOS decreases with the thickness in a way that depends on both the time criterion and on the source-receiver distance. For very thin plates (thickness<λ_bone/4), the apparent SOS tends towards the velocity of the lowest order symmetrical vibration mode