Toward deep transcranial magnetic stimulation

Stimulation of deeper brain structures by transcranial magnetic stimulation (TMS) plays a role in the study of reward and motivation mechanisms, which may be beneficial in the treatment of several neurological and psychiatric disorders. This paper presents numerical simulation of deep transcranial magnetic stimulation (dTMS) by considering double cone, H-, Halo- and multiple concentric circular (MCC) coils. 3D distributions of the induced electric fields in realistic head models were calculated by impedance method and the results were compared with that of figure-of-eight (fo8) coil. Simulation results show that double cone and H-coils have significantly deep field penetration at the expense of induced higher and wider spread electrical fields in superficial cortical regions. The combination of Halo-coil with a conventional circular coil at the top of the head produce deeply penetrating electric field the same as double cone and H-coils, but the stimulation in superficial brain tissues are much lower. The MCC coils provide a flexible way to stimulate deep brain regions with improved focality.