MRI compatible EEG electrode system for routine use in the epilepsy monitoring unit and intensive care unit

Objective: We report on the development of an electroencephalographic (EEG) recording system that is Magnetic Resonance Imaging (MRI) compatible and can safely be left on the scalp during anatomical imaging or used to obtain simultaneous EEG and metabolic or hemodynamic data using functional imaging techniques such as functional MRI or MR spectroscopy. Methods: We assembled a versatile EEG recording set-up with medically acceptable materials that contained no ferromagnetic components. It was tested for absence of excess heating and distortion of the image quality in a spherical phantom similar in size to average adult human head in a clinical 1.5 T GE scanner. After testing its safety in four volunteers, 100 consecutive patients from our epilepsy longterm monitoring unit were studied. Results: There was no change in the temperature of the EEG electrode discs during the various anatomical MRI sequences used in our routine clinical studies (maximum temperature change was - 0.45 degreesC with average head SAR less than or equal to 1.6 W/Kg in the selected subjects) nor were there any reported complications in the others. The brain images were not distorted by the susceptibility artifact of the EEG electrodes. Conclusions: Our MRI compatible EEG set-up allows safe and artifact free brain imaging in 1.5 T MR scanner with average SAR less than or equal to 1.6 W/Kg. This EEG system can be used for EEG recording during anatomical MRI studies as well as functional imaging studies in patients requiring continuous EEG recordings. (C) 2004 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.