Rodent Transcranial Magnetic Stimulation Coil Structure With Controllable Induction Electric Field Direction

Abstract

Animal transcranial magnetic stimulation (TMS) research is meaningful for exploring the mechanism of TMS and promoting the clinical promotion of new therapeutic methods. Tracing back the physiological phenomena caused by TMS is limited by the spatial resolution of the induced electric field. Through human and animal experiments, life science has proven that electric field direction affects the effect of magnetic stimulation, but this factor has not been introduced into the design of animal TMS coils. Therefore, this paper aims to design the TMS coil (EC-X) with controllable induced electric field direction, by finding the most favorable electric field direction for target activation, which can reduce interference to non-target areas and improve stimulation accuracy and energy utilization. Firstly, the structure of EC-X is proposed, establishing the Electromagnetic field Analytical Calculation Model (EM-ACM) for the arbitrarily shaped coil in the air domain, it is theoretically proven that EC-X can achieve direction control of the electric field. Then, the coil structure (such as coil length and angle) is optimized based on maximum ampere-turn ANmax and stimulation focusing degree Fc. Finally, the measurement of xy plane magnetic field distribution proves the accuracy of EM-ACM calculation results, which indirectly proves the feasibility of EC-X. Compared with the Figure-8 coil, EC-X can change the planar electric field direction without moving the coil, which has potential application value.INDEX TERMS Coil, controllable induced electric field direction, transcranial magnetic stimulation.