Magnetic Resonance Elastography (MRE) is a medical imaging modality which aims to image the mechanical properties of tissue. Tissue stiffness maps can be calculated from measurements of the steady-state mechanical response of the tissue undegoing a low frequency (40-200Hz) mechanical excitation, which are taken using modified magnetic resonance imaging (MRI) sequences. There are two classes of methods to perform this stiffness calculation: Iterative inversion, and Direct inversion. Experiments using gelatin phantoms, consisting of a soft background and stiff inclusion, show that both methods accurately locate the inclusion. Iterative inversion provides better quantitative accuracy when compared to independent measurements using a dynamic mechanical analyzer, however, the computation time is significantly longer than direct inversions (iterative methods take hours, whereas direct inversion take seconds). The decision of which method to use for a given application must be made by weighing up the advantages of fast computation time for direct inversion against the better quantitative accuracy of iterative techniques.
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