Helmet-Integrated Transducer Coil Design for Deep Transcranial Magnetic Stimulation

A non-invasive technique successfully applied to various psychiatric and medical conditions is transcranial magnetic stimulation (TMS), which has been applied to modulate brain activity. TMS uses coils that induce a specific electrical field and can stimulate specific neurons or specific areas of the brain. In recent years, a notable variant of TMS has attracted the interest of the medical and scientific community, deep transcranial magnetic stimulation (dTMS). To generate a specific stimulation, it is necessary to be close to the area, yet the coils used in practice to date have not been designed for the specific application but have general shape and dimensions. To generate a concrete and optimized brain stimulus, the coil should be as close as possible to the skull. Therefore, this work analyzes the optimized design of two helmets with integrated coil that specifically stimulate deep regions of the prefrontal cortex and the right temporal lobe. A numerical simulation method, the inclusion-based boundary element method (IBEM), was used to create a new generation of dTMS coils with optimal solutions between depth focusing, power dissipation and stored magnetic energy. Finally, prototypes were fabricated by additive manufacturing on which measurements were made to contrast the results.