Computational electro-magnetic field modeling of TMS coils with validation in gel-based phantom brain

Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique for modulation of cortical neurons in the brain. One challenge with the use of TMS is that it is often difficult to determine the spatial distribution of brain regions receiving stimulation. A popular method of exploring the stimulation profile of TMS coils is through generation of virtual head models and Finite Element Simulations (FEM). However, a limitation of this approach is the models are rarely validated against actual measurements of the magnetic and electric fields. Here, we performed FEM modeling on gel-based phantom brain models with conductive properties that mimic those of the human brain. The phantom brains had implanted electrocorticography electrodes at varying depths to record the stimulation profiles recorded by the electrodes, which were then compared with FEM models of the phantom brain. Ongoing work is focused on validating FEM results relative to a novel paradigm of recording the effects of TMS in neurosurgical patients with intracranial EEG. Taken together, this work highlights the strengths and limitations of using FEM to simulate the magnetic and electric field profiles generated by TMS coils, and propose a new method of testing the performance of novel TMS coils.