Full Characterization of in vivo Muscle as an Elastic, Incompressible, Transversely Isotropic Material Using Ultrasonic Rotational 3D Shear Wave Elasticity Imaging

Using a 3D rotational shear wave elasticity imaging (SWEI) setup, 3D shear wave data were acquired in the vastus lateralis of a healthy volunteer. The innate tilt between the transducer face and the muscle fibers results in the excitation of multiple shear wave modes, allowing for more complete characterization of muscle as an elastic, incompressible, transversely isotropic (ITI) material. The ability to measure both the shear vertical (SV) and shear horizontal (SH) wave speed allows formeasurement of three independent parameters needed for full ITI material characterization: the longitudinal shear modulus mu(L), the transverse shear modulus mu(T), and the tensile anisotropy chi(E). Herein we develop and validate methodology to estimate these parametersandmeasure themin vivo, with mu L = 5.77 +/- 1.00 kPa, mu(T) = 1.93 +/- 0.41 kPa (giving shear anisotropy chi mu = 2.11 +/- 0.92), and chi E = 4.67 +/- 1.40 in a relaxedvastus lateralis muscle. We also demonstrate that 3D SWEI can be used to more accurately characterizemusclemechanical properties as compared to 2D SWEI.

Automated summary

Using a 3D rotational shear wave elasticity imaging setup, this study developed and validated a methodology to measure the mechanical properties of muscle as an elastic, incompressible, transversely isotropic material. By measuring the shear vertical and shear horizontal wave speed, three independent parameters for full material characterization were obtained. The results showed that 3D shear wave elasticity imaging could accurately characterize muscle mechanical properties compared to 2D shear wave elasticity imaging.