Development of Magnetic Resonance Elastography for Assessing Small Regions of Interest in Murine Models

Magnetic Resonance Elastography (MRE) is a noninvasive diagnostic imaging technique capable of determining the mechanical properties of biological tissue and has diagnostic potential for a variety of diseases. Application of MRE for murine studies presents some fundamental challenges such as the fact that higher resolution leads to a loss in the image signal-to-noise ratio (SNR) as a result of reduced voxel size. This challenge is further exacerbated by the dispersive nature of mechanical wave propagation, which results in frequency-dependent regions of wave interferences. Therefore, the mechanical assessment of small regions of interest in mice is a challenging exercise. In this dissertation, a multifrequency based viscoelastic parameter recovery approach known as multifrequency dual elastovisco (MDEV) inversion and intravoxel phase dispersion (IVPD) based MRE or IVPD-MRE have been implemented in the murine MRE pipeline in order to investigate their capability to increase the spatial resolution of elastograms and to improve the stability of the inverse problem in small regions of interest. Studies using phantoms and mouse brain validate the capability of multi-frequency inversion to provide reliable elastograms in small regions of interest, while this is not the case for IVPD-MRE in its current stage of development. The dissertation also presents the application of SampLe Interval Modulation MRE (SLIM-MRE) for assessing viscoelastic changes occurring inside the mouse brain due to the progression of Alzheimer’s disease and inside the mouse liver due to hepatic fibrosis. Combining SLIM-MRE with multifrequency inversion has highlighted early changes inside the cortex and the hippocampus of mice from the Alzheimer’s disease model. SLIM-MRE has also reported higher liver stiffness values in mice which have been medicated to produce fibrotic tissue. Utilizing SLIM-MRE in conjunction with multifrequency-based assessments improves the efficacy of disease diagnosis in the presented preclinical mouse studies.