Comparison between isotropic and anisotropic head model in TMS dosimetry

The numerical estimation of the electric field induced by transcranial magnetic stimulation (TMS) has become increasingly important in the recent decades, requiring more accurate models, in terms of tissue representation and characterization. In this study, a comparison between isotropic and anisotropic subject-specific head models is conducted, to evaluate the effect of anisotropic properties of the brain tissues. The simulations are conducted with a custom-made software able to reconstruct ì patient-specific anisotropic head models, from magnetic resonance and diffusion tensor images. The results indicate that accounting for the anisotropic properties of the brain can impact the estimated induced electric field by up to 20 % in the pre-central sulcus, and 30% in the white matter.