Exposure to a Routine MRI Brain Scan at 1.5 T does not affect Subsequent MEG Examinations

Purpose: We have attempted to investigate whether a routine brain MRI study performed on a clinical whole-body 1.5 T scanner affects a following MEG examination. Material and Methods: Nine healthy volunteers (6 women, mean age 23 years, age range 20–27 years, 3 men, mean age 24 years, age range 23–25 years) underwent one MEG session before and two MEG sessions after MRI of the brain. The first MEG session (MEG1) was finished about 20 minutes before the MRI scans and the second MEG session (MEG2) was performed within 30 minutes after the MRI. The final MEG (MEG3) was performed two hours after MEG2. Each MEG session consisted of a measurement of spontaneous brain activity and an examination with stimulation of the median nerve. The MRI scans included standard T₁w-, T₂w-TSE and gradient echo sequences using a clinical 1.5 T scanner. The repeated-measures design was statistically analyzed using ANOVA for Repeated Measures (General Linear Model) both with and without the Greenhouse-Geisser correction. Results: MEG signals were detected and measured without any problems or interference in all volunteers. There was no statistically significant difference between the noise estimation (p=0.588 corrected; p=0.665 uncorrected) before and after the MRI scans. All volunteers showed measurable dipole localization of the median nerve stimulation before and after MRI. No measurable differences were observed on the frequency maps of spontaneous brain activity before and after MRI (p>0.290 corrected; p 3 0.295 uncorrected). Conclusion: No measurable influences on MEG signals were detected following MRI examinations of human volunteers. With the present study we were unable to replicate the reported findings indicating a strong interaction of an MRI scan on subsequent MEG measurements.