Safety of Simultaneous Intra-Cranial EEG-FMRI: Magnetic Field Gradient Induced Voltages

David W. Carmichael¹, Louis Lemieux¹

MR imaging of patients with implanted intracranial electrodes poses potential health risks, one of which is imaging gradient induced currents that could result in undesired stimulation. Voltages were recorded during an EPI sequence from intracranial electrodes implanted in a realistic test object filled with conductive gel. The main finding was that the measured switching magnetic field gradient induced voltages were small (0.040.01V), in the brain this will correspond to a current well below the medical devices limit for a single fault condition (0.5mA). Hence radiofrequency induced heating is likely to be the primary safety concern.