The effects of frequency variation on the induced fields of transcranial magnetic stimulation systems

Transcranial Magnetic Stimulation (TMS) is a neurophysiological technique that is used as a non-invasive tool for many neurological conditions. This paper addresses the effects of the frequency variation on the induced electric and magnetic fields through electromagnetic simulations. A coil is designed and applied on a realistic human head model at different frequencies and currents. It is observed that in order to choose the optimum frequency of operation several factors including, the safety limits, stimulation threshold and desired magnetic flux density, need to be considered. It is also found that low frequencies offer high magnetic flux density and coil resistance, while high frequencies allow reduction of TMS coil current, power consumption and coil heating. Thus, adequate tradeoffs are required in frequency selection.