Deep Transcranial Magnetic Stimulation 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 paper, a conventional figure-of-eight (Fo8) coil working with the Halo coil [Halo-Fo8 assembly coil (HFA coil)] for deep TMS is numerically designed. The 3-D distributions of magnetic flux density, induced electric field in an anatomically based realistic head model by applying the Fo8 coil, Halo coil, and HFA coil, were numerically calculated by the impedance method. It is found that the design of the HFA coil improves the penetration depth of the magnetic field in brain regions in the right hemisphere, which allows the stimulation of deep brain tissues than is achievable with the Fo8 coil.