Scaling Personalized TMS: A Scalp-Based MRI-guided Alternative to Neuronavigation

Background: Personalized transcranial magnetic stimulation (TMS) has shown promise in treating psychiatric and neurological disorders, but its accessibility is limited by reliance on costly and complex neuronavigation systems, particularly in resource-constrained clinical settings. Objective: To develop and validate a scalp-based alternative to neuronavigation for personalized TMS targeting. Methods: We developed a Continuous Proportional Coordinate (CPC) system-based approach for personalized TMS targeting and validated its performance through three operators across ten participants, using individualized DLPFC-SGC targets as an example. The validation framework included targeting consistency assessment, reproducibility evaluation, and cross-cortical generalizability analysis. Results: The CPC-based approach demonstrated comparable performance to neuronavigation, achieving 99.4% of its electric field strength (74.80 vs. 75.14 V/m; r=0.962) and 93.9% of DLPFC-SGC functional connectivity (-0.216 vs. -0.230; r=0.949), with high inter-operator reliability (ICC≥0.903). Reproducibility analysis showed strong correlation between sessions (r=0.948-0.957) with high reliability. Further simulations across 1,125 uniformly distributed cortical targets supported generalizability of this approach, with stable electric field preservation (99.07±1.54%) across different brain regions. Conclusions: The CPC-based approach offers a practical alternative to neuronavigation, maintaining targeting accuracy and providing a more accessible option for personalized TMS implementation.