Comparison of the Effect of Coil Configuration and the Variability of Anatomical Structure on Transcranial Magnetic Stimulation

Transcranial magnetic stimulation (TMS) is a non-invasive technique that uses transient magnetic field generated from electromagnetic coils in inducing electric field to stimulate the neurons of the brain. Various researchers have proposed coil designs for TMS aimed at achieving high focality and increased penetration depth of the induced electric field in the brain. In this article, the authors compare the figure of eight (FOE) coil, quadruple butterfly coil (QBC), and triple halo coil (THC) on different head models to confirm the effect of coil configuration on the induced electric field. Finite element simulations were conducted with Sim4life software to determine the maximum electric field intensity, E-Max (V/m) and the stimulated volume of the brain, V-Half (m
³
). The coils were positioned on the head model and at the dorsolateral prefrontal cortex (DLPFC) location of the head model, and the E-Max and V-Half values were compared for the different head models to confirm the effect of coil configuration and the variability of the anatomical structure.