Deep Transcranial Magnetic Stimulation with Improved Focality Using Figure-of-Eight and Halo Coils

The 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 to the treatment of several neurological and psychiatric disorders. In this work, the Halo coil working with a conventional figure-of-eight (Fo8) coil (Halo-Fo8 assembly coil (HFA coil) with varied bending angle of Fo8 coil wing for deep TMS (dTMS) is numerically designed. 3-D distributions of magnetic flux density, induced electric field in an anatomically based realistic head model were numerically calculated by the impedance method. It was found the HFA coil with varied bending angle of Fo8 coil wing can be employed to realize the dTMS with controllable stimulation depth and focality.