Demonstration of Complex Shear Wave Patterns in Skeletal Muscle in vivo Using 3D SWEI

Shear wave elastography imaging (SWEI) of skeletal muscle has previously been used to identify speeds along and across the fibers, with limited success and low repeatability. In this work we show how a tilted configuration can be used to fully characterize muscle as an elastic incompressible TI material using ultrasonic techniques. In the vastus lateralis of a healthy volunteer, a 3D rotational shear wave elastography imaging (SWEI) setup was used to identify shear wave speeds in all directions. Due to the inherent tilt of the muscle fibers relative to the transducer face, multiple shear wave fronts are created. In an elastic incompressible transversely isotropic (TI) material these are the shear vertical (SV) and shear horizontal (SH) mode. By measuring both wave modes and comparing to matched Green's function simulations, this work measures for the first time in vivo all three parameters necessary to fully characterize an elastic incompressible TI material.