STIMULATION OF PERIPHERAL-NERVES BY TIME-VARYING MAGNETIC-FIELD GRADIENTS DURING MAGNETIC-RESONANCE TOMOGRAPHY

Purpose: The objective of this study is to explain how peripheral nerv es can be stimulated by magnetic resonance imaging (MRI) and to descri be the associated potential risk. Present knowledge on the bioeffects of time-varying magnetic fields used in MRI are summarized and discuss ed. Material and Methods: This review summarizes current reports on pe ripheral nerve stimulation during MRI and studies which determine thre shold values for stimulation effects. Results/Discussion: The comparis on of the different studies indicates that it is reasonable to express the stimulation threshold in terms of the gradient amplitude rather t han in terms of the rate of change of the magnetic field gradient. Fur ther studies are necessary to obtain reliable threshold values for per ipheral nerve stimulation during MRI and, even more important, to find out how these results can be used to define threshold values in order to avoid excitation of the myocardium during MRI.