Group Shear Wave Speed Viscoelastic Analysis using 3D Rotational Volumetric Shear Wave Imaging in Relaxed and Contracted in vivo Muscle

To characterize muscle tissue as a viscoelastic transversely isotropic material, we use rotational volumetric shear wave elasticity imaging (SWEI) and group speed viscoelastic analysis. We performed these measurements in vivo in the vastus lateralis of two healthy volunteers, both at rest and in varying degrees of contraction. We found a high degree of repeatability in our at rest elasticity measurements, determining that the stiffness along the fibers is higher than across the fibers. The viscosity at rest is approximately equal and low in both directions. In our contraction analysis, we found that stiffness increases substantially along the fibers and increases slightly across the fibers with increasing contraction. No clear trends were observed between viscosity and contraction level. Future work will improve the method of model-based viscoelastic characterization within the context of transversely isotropic materials and expand this analysis to more subjects.

Automated summary

By utilizing rotational volumetric shear wave elasticity imaging (SWEI) and group speed viscoelastic analysis, we characterized the viscoelastic properties of muscle tissue in different states. The study revealed differences in stiffness along and across the fibers, with stiffness increasing significantly along the fibers during contraction. However, there was no clear relationship observed between viscosity and contraction level.