Model gradient coil employing active acoustic control for MRI.

Results are presented for a model three-axis gradient coil incorporating active acoustic control which is applied to the switched read gradient during a single-shot rapid echo-planar imaging (EPI) sequence at a field strength of 3.0 T. The total imaging acquisition time was 10.6 ms. Substantial noise reduction is achieved both within the magnet bore and outside the magnet. Typical internal noise reduction over the specimen area is 40 dB(A) whereas outside the acoustic chamber the noise level is reduced by 60-67 dB(A). However these results are relative to a control winding which is switched in phase, adding 6 dB(A) in its non-optimized mode, which is included in the quoted figures.