Actuation Systems for MR Elastography

One main issue with magnetic resonance elastography is the design of an actuation system to enable adequate mechanical excitation within the magnetic field of the magnetic resonance (MR) imager. Pneumatic, electromagnetic, and piezoelectric actuation systems have been employed for MRE examinations of the skeletal muscle, the brain, the breast, and abdominal organs. Although pneumatic systems are restricted to lower frequencies roughly below 100 Hz and electromagnetic actuators can interfere with magnetic imaging gradients, piezoelectric systems provide highly stable and precise actuation for a frequency range up to 500 Hz with amplitudes up to 1 mm. The design of a piezoelectric actuator allowing such a broad range of excitation will be presented.