Fundamental study on peripheral nerve stimulation with lf time-varying magnetic field

Numerical simulation of human and xenopus myelinated nerve magnetic stimulation was executed to compare their excitation thresholds at Low Frequency (LF) band. Currently LF band magnetic field exposure is suppressed during Magnetic Resonance (MR) scanning to avoid possible unexpected sensation and motion, which limits the resolution of MR images. Recently, Weinberg and his colleague reported higher threshold of human peripheral nerve against magnetic field at LF band in their experimental study. Using equvalent circuits of human and xenopus myelinated nerves, their thresholds for LF magnetic field stiumulation were investigated. As a result, the excitation threshold of human nerve for LF magnetic field stimulation with biphasic cosine wave increased exponentially around 100kHz as the frequency increased, which is consistent with the finding ofWeinberg et al. and was not observed in xenopus nerve equivalent circuit. The lower axoplasm resistivity of human nerve was considered to be the cause of this feature.