An approach to MRI-based dosimetry for transcranial magnetic stimulation

A new MRI-based measurement of the magnetic vector field distribution generated by a transcranial magnetic stimulation (TMS) probe is introduced in this study. Projections of the static magnetic field produced by a DC current in a TMS probe onto the axis of the scanner's main field (B0) can be measured using a conventional B0 field-mapping technique. The remaining Cartesian components can then be calculated from projections obtained at different orientations of the sample and probe. The measured static field can then be scaled to calculate the effects of a dynamic TMS pulse. This article includes a study demonstrating the feasibility of this approach on a phantom and a human subject.