Characterization of Compressive and Shear Moduli in Transversely Isotropic Materials using Viscoelastic Response (VisR) Ultrasound

Viscoelastic response (VisR) ultrasound has been demonstrated for assessing the shear elastic moduli of transversely isotropic (TI) materials when the applied acoustic radiation force (ARF) excitation is normal to the material axis of symmetry (AoS). This in silico study evaluates the potential for non-normal ARF excitations to interrogate both shear and compressive elastic moduli in TI materials. VisR relative elasticity (RE) was derived from displacements induced by ARFI excitations that were electronically steered in transversely isotropic materials that were tilted with respect to the transducer face. The resulting RE measures varied with ARF-AoS incidence angle, and the degree of variation correlated with the ratio of longitudinal shear-to-compressive moduli (μ
L
/E
L
). These results suggest that steering the ARF excitation over a range of ARF-AoS incidence angles may enable evaluation of a new mechanical biomarker, μ
L
/E
L
, in anisotropic tissues.