Development of Overlapped Designed Coils for Transcranial Magnetic Stimulations

Transcranial magnetic stimulation (TMS) is a noninvasive neuromodulation technique used to treat a variety of neurological disorders, including major depression. The development of the deep brain TMS coil for stimulating subcortical structures expands the use of TMS beyond the stimulation of superficial cortical targets. Deep brain stimulation may have beneficial effects on neurological disorders such as Parkinson's disease, post-traumatic stress disorder and mild traumatic brain injury. Previous studies have shown that cerebellum plays a very big role in behavior and motor planning. To stimulate the specific areas of the human brain we require TMS coil with precise focal abilities for that the material, design, and position of a TMS coil plays a significant role in adjusting focusing power of the coil. Therefore, in this letter, we studied stimulation of frontal brain and cerebellum with two different new coil designs positioning on different locations. A rare design of TMS coil made with Litz wire is proposed to enhance excitation focality in the brain and compared with traditional figure-of-eight (FOE) coil and double cone coil (DC). Finite-element simulation tool ANSYS Maxwell 3D has been used to simulate and compare the magnetic field and electric field induced inside the model of human brain. The coil studies are as follows: a figure-of-eight (FOE) coil, an overlapped copper coil, and a Litz wire overlapped coil. This was followed by experimental validation which shows great agreement with the simulation results.