Purpose: To develop a method of compact tabletop magnetic resonance elastography (MRE) for rheological tests of tissue samples and to measure changes in viscoelastic powerlaw constants of liver and brain tissue during progressive fixation. Methods: A 10-mm bore, 0.5-T permanent-magnet-based MRI system was equipped with a gradient-amplifier-controlled piezo-actuator and motion-sensitive spin echo sequence for inducing and measuring harmonic shear vibrations in cylindrical samples. Shear modulus dispersion functions were acquired at 200-5700 Hz in animal tissues at different states of formalin fixation and fitted by the springpot powerlaw model to obtain shear modulus l and powerlaw exponent a. Results: In a frequency range of 300-1500 Hz, unfixed liver tissue was softer and less dispersive than brain tissue with l ¼ 1.68 6 0.17 kPa and a ¼ 0.51 6 0.06 versus l ¼ 2.60 6 0.68 kPa and a ¼ 0.68 6 0.03. Twenty-eight hours of formalin fixation yielded a 400-fold increase in liver l, 25-fold increase in brain l, and two-fold reduction in a of both tissues.

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BS-gradients were demonstrated as a feasible option for spatial phase encoding. Furthermore, undistorted BS-SET images could be obtained using the proposed reconstruction method.

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