Development of Overlapped Designed Coils for Transcranial Magnetic Stimulations

Transcranial magnetic stimulation (TMS) is a noninvasive neuromodulation technique that is 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 the cerebellum plays a very big role in behavior and motor planning. To stimulate the specific areas of the human brain, we require a TMS coil with precise focal abilities because the material, design, and position of a TMS coil play a significant role in adjusting the coil's focusing power. Therefore, we studied stimulation of the frontal brain and cerebellum with two different new coil designs positioned on different locations. A rare design of the TMS coil made with Litz wire was developed to enhance excitation focality in the brain and was compared with a traditional figure-of-eight (FOE) coil and double-cone coil. The finite-element simulation tool ANSYS Maxwell 3-D has been used to simulate and compare the magnetic field and electric field induced inside the model of the human brain. The coil studies are as follows: a 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.