Verification of effect of analytical conditions of shear wave velocity on ability to evaluate microstructure

In this study, the relationship between the analytical conditions of shear wave velocity (SWV) and the evaluation ability of microstructure were verified by FDTD simulation. By adding acoustic radiation force (ARF) to the left edge of the simulation space, which mimicked various fatty livers with different fat mass, shear waves propagating in the lateral direction were simulated in each liver. SWV was calculated using the time difference calculated by the cross-correlation method from two timewaves laterally located in the simulation. By varying the resolution of the SWV evaluation, the effect of scattering and refraction of shear waves in fat droplets, etc. on the macroscopic shear propagation was evaluated. Although shear waves could be evaluated stably when tracking shear waves at the spatial step (time width) of the clinical device level, the effects of individual fatty substances were strongly indicated when tracking in the microscopic sense of 10 μm (50 ns). When there was a thick fat layer or a sparse muscle layer near the body surface, the irradiation of ARFI did not work as expected and the evaluation accuracy of SWV decreased.