Effect of routine MR imaging of the brain at 1.5 T on subsequent magnetoencephalography: results in nine volunteers.

Abstract

To investigate whether routine magnetic resonance (MR) imaging of the brain with a whole-body 1.5-T imager affects the results of subsequent magnetoencephalography (MEG). Nine healthy volunteers (six women, mean age of 23 years, age range of 20-27 years; three men, mean age of 24 years, age range of 23-25 years) underwent one MEG session before and two MEG sessions after MR imaging of the brain. The first MEG session was completed about 20 minutes before brain MR imaging began, the second MEG session (MEG 2) was performed within 30 minutes after MR imaging, and the third MEG session was performed 2 hours after MEG 2. Each MEG session involved measurement of spontaneous brain activity and, in seven patients, of brain activity during stimulation of the median nerve. MR imaging included T1- and T2-weighted fast spin-echo and gradient-echo sequences applied with a 1.5-T clinical imager. Data were compared by using a repeated-measures analysis of variance (general linear model) both with and without Greenhouse-Geisser correction. MEG signals were detected and measured without difficulty in all volunteers. No statistically significant difference was seen between estimated noise at MEG before and after MR imaging (P =.588 with correction, P =.665 without correction). MEG records obtained in all volunteers enabled localization of evoked response to median nerve stimulation before and after MR imaging. No measurable differences were observed between relative power spectra of spontaneous brain activity before and after MR imaging (P >.290 with correction, P >or=.295 without correction). No measurable effect of 1.5-T brain MR imaging on subsequent MEG was detected.