IN VIVOCHARACTERIZATION OF THE MUSCLE VISCOELASTICITY IN PASSIVE AND ACTIVE CONDITIONS USING MULTIFREQUENCY MR ELASTOGRAPHY

Abstract

This study aims to develop a viscoelastic database for muscles (VM: vastus medialis and Sr: sartorius) and subcutaneous adipose tissue with multifrequency magnetic resonance elastography (MMRE) coupled with rheological models. MMRE was performed on 13 subjects, at 70-90-110 Hz, to experimentally assess the elastic properties (μ) of passive and active (20% MVC) muscles. Then, numerical shear modulus (μ) and viscosity (η) were calculated using three rheological models (Voigt, Zener, Springpot). The elastic properties, obtained with the Springpot model, were closer to the experimental data for the different physiological tissues (μSpringpot_VM_Passive= 3.67 ± 0.71 kPa, μSpringpot_Sr= 6.89 ± 1.27 kPa, μSpringpot_Adipose Tissue= 1.61 ± 0.37 kPa) and at different muscle states (μSpringpot_VM_20%MVC= 11.29 ± 1.04 kPa). The viscosity parameter increased with the level of contraction (η_VM_ Passive_Springpot= 4.5 ± 1.64 Pa.s versus η_VM_20% MVC_Springpot= 12.14 ± 1.47 Pa.s ) and varied with the type of muscle. (η_VM_ Passive_Springpot= 4.5 ± 1.64 Pa.s versus η_Sr_Springpot= 6.63 ± 1.27 Pa.s). Similar viscosities were calculated for all tissues and rheological models. These first physiologically realistic viscoelastic parameters could be used by the physicians to better identify and monitor the effects of muscle disorder, and as a database for musculoskeletal model.