Measurement of visual evoked potential during and after periods of pulsed magnetic field exposure.
OBJECTIVE
To study the effect of switched magnetic fields used in MR scanners on the visual evoked potential (VEP) in human subjects.


METHODS
We have used an MRI gradient coil, remote from an MRI magnet to produce a time-varying magnetic field (0.5 kHz, peak field approximately 8.7 T/second) in the human brain without the confounding effects of static field exposure or accompanying acoustic noise. The VEP response to a 2-Hz reversal, 8 x 8 checkerboard, occupying 20 degrees of the visual field was recorded from occipital locations O1 and O2. VEP recordings were made every five minutes before, during, and after a 10-minute magnetic field exposure period for seven subjects.


RESULTS
In contradiction to studies previously reported in the literature for fields of 50 Hz and 60 mT, no significant effects on the peak amplitude or latency of the VEP P100 O1 and O2 responses were found.


CONCLUSIONS
Switched magnetic fields of a level and frequency comparable to those used in MRI do not have a significant effect on primary retinal or visual processing.
Glover
Paul M
PM
School of Physics and Astronomy, University of Nottingham, Nottingham, UK. Paul.Glover@Nottingham.ac.uk
Eldeghaidy
Sally
S
Mistry
Tejal R
TR
Gowland
Penny A
PA
D000328:Adult; D004307:Dose-Response Relationship, Radiation; D004569:Electroencephalography / Q000379:methods; D004574:Electromagnetic Fields; D005074:Evoked Potentials, Visual / Q000502:physiology* / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage