Evaluation of the Effect of an Anisotropic Medium on Shear Wave Velocities of Intra-Muscular Gelatinous Inclusions

In highly anisotropic biological tissues such as muscle or tendons, calculating Young's modulus from the shear wave speed (csw) by using shear wave elastography (SWE) involves a complex transversally isotropic rheological model not yet used in common practice. To our knowledge, the effect of muscle anisotropy on csw of intra-muscular lesions has not yet been investigated. The objective of our study was to define the effect of an anisotropic medium on csw of intra-muscular gelatinous inclusions. We conducted a prospective monocentric, in vitro study in order to examine the quantitative and qualitative SWE behavior of a 9-mm gelatinous intra-muscular implant depending on the orientation of the probe relative to the muscle fibers. There were very significant differences in the prevalence of SWE signal void (p < 0.01) and in the csw (p < 0.01) in the gelatinous intra-muscular implants depending on the orientation of the probe relative to the fibers. Performing the csw measurements of centimetric intra-muscular lesions by orienting the probe perpendicular to the fibers decreases the probability of artifacts occurring at high intensity interfaces.