Transcranial magnetic stimulation coils

Many different types of TMS coils have been proposed and implemented, but all share certain common features. The induced electric field is always maximum in the superficial parts of the brain, nearest the coil, and attenuates toward the center of the head. Power requirements are high. Design tradeoffs are present between specific coil features including focality, relative penetration, size, weight, efficiency, heating, and noise. Because of the high voltages and currents involved, electrical safety, cooling, and the need for hearing protection must always be considered. Special situations such as placebo stimulation, small animal studies, and stimulation inside MRI systems generally require coils designed specifically for these applications.