The 3-dimensional magnetic field distribution for a figure-eight Transcranial Magnetic Stimulator was investigated by theoretical and experimental means.  When the TMS stimulator was set at 50% of the maximal power output, the peak magnetic field produced by the TMS coil was found to be 0.40 +/- 0.24 Tesla experimentally and 1.0 Tesla theoretically at a distance of 1.1 +/- 0.3cm above the coil.  As you moved further away, the magnitudes fell rapidly and the focusing peak magnetic field diminished.  At a distance of 1.6 +/- 0.5cm, the peak field was found to be 0.30 +/- 0.18 Tesla experimentally and 0.45 Tesla theoretically.  Even further away, at a distance of 2.1 +/- 0.5 cm, the peak field was determined to be 0.30 +/- 0.20 Tesla experimentally and 0.30 Tesla theoretically.

    The structure of the TMS coil produced a unique magnetic field distribution.  The focusing power of the TMS coil was characterized by the unique shape and the distance at which the stimulation is applied.  The closer the placement of the stimulator, the greater the magnitude of the magnetic field being used to induce current in the cerebral cortex.  The focusing peak was also found to be more distinct in shape and sharp when the TMS coil is closer to the area of stimulation.