Viscoelastic shear properties of in vivo thigh muscles measured by MR elastography.

ABSTRACT

PURPOSE: To measure the viscoelastic properties of passive thigh muscles using multifrequency magnetic resonance elastography (MMRE) and rheological models. MATERIALS AND METHODS: Four muscles in five volunteers underwent MMRE tests set up inside a 1.5T magnetic resonance imaging (MRI) scanner. Compression excitation was generated with a driver attached around the thigh, and waves were generated at 70, 90, and 110 Hz. In vivo experimental viscoelastic parameters (G(ω) = G' + i G″) were extracted from the wavelength and attenuation measurements along a local profile in the direction of the wave's displacement. The data-processing method was validated on a phantom using MMRE and RheoSpectris tests. The complex modulus (G(ω)) related to elasticity (µ) and viscosity (η) was then determined using four rheological models. RESULTS: Zener was the best-fit model (χ ∼0.35 kPa) for the rheological parameters of all muscles. Similar behaviors for the elastic components for each muscle were found for the Zener and springpot models. The gracilis muscle showed higher elastic values (about 2 kPa) in both models compared to other muscles. The α-values for each muscle was equivalent to the ratio G″/G' at 90 Hz. CONCLUSION: MMRE tests associated with data processing demonstrated that the complex shear modulus G(ω) of passive muscles could be analyzed using two rheological models. The viscoelastic data can be used as a reference for future assessment of muscular dysfunction. J. Magn. Reson. Imaging 2015. J. Magn. Reson. Imaging 2016;431423-1433.