Design, construction, and deployment of a multi-locus transcranial magnetic stimulation system for clinical use

Background: Transcranial magnetic stimulation (TMS) is an established method for noninvasive brain stimulation, used for investigating and treating brain disorders. Recently, multi-locus TMS (mTMS) has expanded the capabilities of TMS by employing an array of overlapping stimulation coils, enabling delivery of stimulation pulses at different cortical locations without physical coil movement. We aimed to design, construct, and deploy an mTMS device and a five-coil array for clinical environment, emphasizing safety of the system. Methods: Our mTMS device is controlled by a field-programmable gate array (FPGA). The power electronics comprises five stimulation channels, each consisting of a high-voltage capacitor connected to a pulse circuit, controlling a single coil in the array. The device contains custom-designed circuit boards, with functions such as monitoring the system state, reporting errors, and delivering pulses. Our design utilizes redundancy in both hardware and firmware to ensure robust operation and safety. We performed an automated motor mapping test to verify the electronic targeting capabilities of the device. Results: We constructed the mTMS device and deployed it to the Hertie Institute for Clinical Brain Research (Tübingen, Germany). Compared to our earlier prototype, the new design improves patient and operator safety. The motor mapping test confirmed that our device can accurately target stimulation pulses in the cortex. Significance: mTMS or other similar technologies are currently not available for hospital use. The present device and its installation are major steps toward establishing multicoil TMS as an accessible clinical tool for investigation and treatment of the brain.