title: Physiologic effects of intense MR imaging gradient fields.
abstract: The strength duration relationship for peripheral nerve stimulation by MR imaging pulsed gradient magnetic fields was measured in 84 human subjects. The data were fitted to the hyperbolic strength-duration relationship: dB/dt=b(1 + c/d), where b is rheobase, c is chronaxie, and d is duration, and dB/dt is reported as the maximal value on the axis of the bore. For sensation threshold, average (b,c) (15 T/s, 0.37 ms) for the y-gradient and (26 T/s, 0.38 ms) for the z-gradient coil. The dB/dt intensity to induce a sensation which the subject described as uncomfortable was about 50% above the sensation threshold. Experiments with dogs showed that the cardiac stimulation by pulsed magnetic gradient fields is exceedingly unlikely.
mesh_terms: D000009:Abdominal Muscles / Q000502:physiology; D000328:Adult; D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D008280:Magnetics / Q000009:adverse effects; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation; D010146:Pain / Q000209:etiology*; D017288:Pain Threshold / Q000502:physiology; D012119:Respiration; D012677:Sensation / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology; D013909:Thorax / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology