Nonlinear storage modulus quantification with MR-elastography: from in vitro to in vivo assessment

Motivation: Estimating the nonlinear coefficient in MR elastography could provide a relevant mechanical parameter for tumor characterization. Goal(s): The goal of this study was to develop a method for assessing the nonlinear coefficient in MR elastography. Approach: We developed a specific MR elastography setup and a post-processing pipeline to quantify nonlinear coefficients in phantoms and mice with a tumor implanted subcutaneously. Results: In phantoms, we observed that nonlinear coefficient was able to provide a higher contrast than storage modulus to distinguish different structure. In addition, in mice, nonlinear coefficient was correlated to the entropy which is a marker of collagen distribution irregularity. Impact: The estimation of the nonlinear coefficient provides a new biomarker to assess tissue mechanical parameters. The relation between this parameter and tissue structure could be relevant in tumor investigation, as tissue microarchitecture is an important marker of tumor severity.