Dynamic MRE is based on the visualization of propagating shear waves in harmonically excited samples. Shear waves are typically generated by electromechanical actuators fed by pattern generator / audio amplifier devices. Excitation frequencies range between 50 and 500 Hz.  Minimum amplitudes for particle displacement are in the order of 10 um. The wave patterns, which depend on the local biomechanical properties of the sample, are visualized by motion-sensitive MRI techniques synchronized to the mechanical excitation. The figure below shows the experimental setup.