In vivo MR elastography of liver: Comparison to oscillatory rheometer studies of tissue specimen

Introduction: Magnetic Resonance Elastography (MRE) is capable to measure the mechanical properties of living tissue by externally introduced shear vibrations and phase contrast MRI [1]. In multifrequency MRE the complex shear modulus G*(ω) of biological tissue is measured at various mechanical vibration frequencies simultaneously. Viscoelastic tissue parameters can then be calculated by fitting G*(ω) to the dispersion relations of rheological models [2]. Problem: In previous studies various rheological models have been proposed to analyze the viscoelastic behavior of liver tissue [2-9]. However, no comparison of MRE data to standard rheometer tests was performed. Objective: In this study G*(ω) is measured in ex vivo bovine liver in the frequency range 2.5 Hz – 70 Hz using an oscillatory rheometer device. The resulting dispersion relations are compared to those acquired by multifrequency MRE of in vivo human liver.