Post Hoc Localization of Beam F3 Stimulation Targets: An MRI-Derived Geodesic Approach for Refined TMS E-Field Simulations

The study addresses a method for more precise identification of transcranial magnetic stimulation (TMS) targets in the left dorsolateral prefrontal cortex, used in depression treatment. The research team developed a new procedure based on MRI images that uses geodesic measurements on the brain's scalp surface to accurately determine individual stimulation positions. The method was validated retrospectively in 20 patients and prospectively in 2 healthy subjects using visible skin markers. Results showed that the difference between digital measurements and actual measurements was minimal (0.11 to 0.14 cm). The new approach provides more accurate simulations of the electric field in the brain compared to previous group-template-based methods. This method enables retrospective analysis of existing patient cohorts and may help identify predictors of treatment response.