PERIPHERAL-NERVE STIMULATION BY TIME-VARYING MAGNETIC-FIELDS

Purpose: A study was performed to assess the stimulation threshold for healthy adults using sinusoidally oscillating gradients. Method: One hundred thirteen healthy adults were examined in the study. ECG and ph ysiological parameters were measured. All measurements were performed of both the head and the abdomen. The subjects were measured in the su pine position with the region of interest positioned in the center of the gradient coils. The measurement was performed for three orthogonal , four oblique, and double oblique orientations. Results: No volunteer reported painful, severe stimulation. The mean thresholds for periphe ral stimulation in head and body measurement were similar: 85.5% of st imulation during examination of the head and 87.6% during measurements of the abdomen were reported when the y-gradient was used. Conclusion : The greatest frequency of reported stimulations occurs when the y-gr adient is used. This was confirmed by the results and supports the hyp othesis that orthogonal to the y-axis the body has its largest conduct ive loop, resulting in the strongest peripheral stimulation.