PERIPHERAL-NERVE STIMULATION IN A WHOLE-BODY ECHO-PLANAR IMAGING-SYSTEM

Echo-planar techniques in MRI use a rapidly oscillating frequency-enco ding gradient with the potential to produce peripheral nerve stimulati on, To evaluate the incidence, type, and location of stimulation in a commercial whole-body scanner, we studied two groups: (a) 173 consecut ive individuals scanned by echo-planar imaging for other purposes and (b) seven subjects who were scanned with an extensive set of 36 echo-p lanar sequences (with prompting after each scan to report any peripher al nerve stimulation) to test the effects of various parameters. Altho ugh only 5% of group A reported symptoms of peripheral nerve stimulati on, all in group B experienced some type of stimulation, dependent pri marily on direction of the oscillating gradient and location of the bo dy within the gradient coil. Maximum stimulation typically occurred 30 to 40 cm from isocenter in the region of maximum dB/dt. Generally, y gradients produced truncal stimulation, and x gradients produced stimu lation in the head. When hands were clasped over the abdomen, a tingli ng in the hands occasionally was felt, Patients should be instructed t o keep their hands apart.