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Lorentz-force-induced vibrations in MRI systems cause significant acoustic noise levels during scanning, the main acoustic noise source being the vibrating gradient coil. In this paper, a novel active vibration control technique is presented to reduce vibrations of the gradient coil, and hence, achieve a reduction of acoustic noise during scanning. The active vibration control technique uses seismic masses that are actuated by means of piezo actuators to create forces on the gradient coil counteracting its vibrations. Using four seismic mass actuators, a vibration reduction of 3-8 dB at resonance frequencies is achieved, giving an overall vibration reduction of 3 dB for a typical field gradient (FE)-echo planar imaging (EPI) gradient sequence, as substantiated by measurements. Using eight actuators, an overall vibration reduction of 5 dB is predicted for this sequence.
Date of Publication: June 2008