Pooled analyses of effects on visual and visuomotor performance from exposure to magnetic stray fields from MRI scanners: Application of the Bayesian framework

Abstract

To pool measurement data from individual studies on acute and temporal neurobehavioral effects of stray fields and re-analyze these using a Bayesian framework. Data from tests assessing effects of exposure to stray fields (<1600 mT) from MRI systems (1.5-7.0 T) on visuomotor and visual sensory systems collected in three relatively small case-crossover studies of volunteers seated in the magnet stray field were analyzed together using hierarchical regression models. Bayesian prior distributions were specified such that a priori an association with electromagnetic field (EMF) exposure was absent, and were updated with measurement data into posterior distributions. The posterior distributions suggested that visuomotor speed, but not precision, was affected by exposure (-0.2% to -0.7% per 100 mT). The visual contrast threshold at stronger contrasts also increased with increased EMF exposure (-1%/100 mT). Using a Bayesian framework with conservative priors appeared to be an effective technique to assess subtle effects of exposure to stray magnetic fields. The posterior distributions were dominated by the observed data, which provides additional compelling evidence that the visuomotor domain and the visual contrast threshold level are negatively affected in the presence of stray fields of 1.5-T to 7.0-T MRI systems.