Intensity and Localization of Eddy Currents in Transcranial Magnetic Stimulation to the Cerebellum

We performed numerical simulations of the eddy current induced by transcranial magnetic stimulation (TMS) to the cerebellum. Solutions were obtained on a three-dimensional human head model with inhomogeneous conductivity. The stimulating coil consisted of a pair of circular coil elements with a diameter of 110 mm. Electric current applied to the coil had an intensity of 44.2 kA middot Turn, which resulted in a magnetic field intensity of 0.56 T at the center of a coil element. The maximum current density in the cerebellum was 2.9 A/m
²
. Distribution of the eddy current in the cerebellum was limited to approximately 1 cm beneath the surface of the cerebellum. The eddy current had a localized distribution in the cerebellum, while the magnetic field had a broad distribution