Analyzing the Shear Wave Mechanics in Cardiac Shear Wave Elastography Using Finite Element Simulations

Shear wave propagation in cardiac shear wave elastography (SWE)is subjected to the changing myocardial fiber orientation across tissue thickness, leading to spatially varying speeds. Using a finite element framework for cardiac SWE, we demonstrate that tissue thickness is an extra determinant for shape and directionality of the shear wave magnitude, next to fiber orientation. In addition, the direction of mechanical loading with respect to fiber orientation and the magnitude of the fiber gradient across tissue thickness both affect magnitude and spatial features of the shear wave speed. Characteristics of the acoustic radiation source also affect shear wave speed but this dependency can be eliminated by applying a push with a large depth of field.