Experimental characterization of a figure of eight coil for transcranial magnetic stimulation

In order to accurately evaluate the induced E field distribution inside the brain due to a transcranial magnetic stimulation (TMS) procedure, a complete characterization of the stimulating source is needed. In this paper, a full experimental characterization of a typical TMS coil is given, providing spatial distribution of the generated B field as well as input impedance and waveform of the current. Measurements show a slight deviation in the field distribution with respect to the one coming from idealized coil models, particularly for what concerns symmetry.