Quantification of the anisotropic biomechanical properties of the lower leg muscles during muscle contraction using MR elastography and DTI

Motivation: Determining the in vivo mechanical properties of synergist muscles is challenging. Goal(s): In this study, we developed an anisotropic inversion method for MR elastography (MRE) to quantify biomechanical parameter changes in lower leg muscles during passive plantarflexion and dorsiflexion. Approach: Based on DTI and multifrequency MRE in 13 male volunteers, stiffness reconstruction was performed after aligning MRE with DTI coordinate systems. Isotropic shear wave speed (ciso) and anisotropic shear wave speed, parallel (c$$$_{\parallel}$$$) and perpendicular (c$$$_{\perp}$$$) to the fiber orientation were obtained. Results: Our findings showed significant changes of biophysical properties during muscle movements, particularly c$$$_{\parallel}$$$ and c$$$_{\perp}$$$ are more sensitive than ciso.Impact: Anisotropic muscle stiffness measured by DTI-MRE provides a consistent biomarker sensitive to changes in muscle structure and alignment altered by passive muscle movements such as plantarflexion and dorsiflexion.