Investigating the Distribution of Induced Electric Field Generated by Double Square Semicircle Coil in Transcranial Magnetic Stimulation

Transcranial magnetic stimulation (TMS) is a physical technique that modulates the human brain nervous system and can be used as a non-invasive treatment for neurological diseases. To address the problem of poor focusing performance of TMS coils, this study first designs a new coil geometry, Double Square Semicircle (DSS) coil, based on traditional coil stimulation characteristics. Second, this study uses the Sim4Life finite element simulation software to compare the stimulation characteristics of DSS coil and six traditional coils under the head model, proving that the induced electric field generated by DSS coil has high-focusing performance. Third, this paper explores the effects of four physical parameters - the distance between the human brain model and the coil, different stimulation directions, coil size and coil bending angle - on the spatial distribution of the induced electric field. After the above simulation experiments, the optimal design scheme of DSS coil is found. Experimental results show that, compared with several traditional coils, the focusing effect can be improved by up to 77.49%, proving that DSS is a high-focusing performance TMS coil, which is suitable for future TMS high-precision treatment needs.