Population-Optimized Electrode Montage Approximates Individualized Optimization in Transcranial Temporal Interference Stimulation

Background: An essential aspect of applying transcranial temporal interference stimulation (tTIS) is optimizing the electrode configuration to enhance performance when targeting deep brain structures. Efficient optimization of the electrode montage can be achieved using electric field analysis on individualized head models, based on high-resolution structural MR. One important limitation of this approach is the increased cost, which involves the acquisition of high-resolution structural MRI, specialized software, and navigation systems for accurate electrode positioning, limiting its practicality in clinical contexts due to affordability and accessibility challenges. An alternative is to develop a standardized electrode montage designed to maximize the intracranial electric field across a representative population of the target individual. However, it remains unclear how well a population-based approach can approximate the precision of individualized optimization.Aim: This study evaluates the feasibility of using group-level electric field analysis to optimize the tTIS montage. Specifically, it seeks to maximize the intracranial electric field using a population-proxy approach and compare its efficacy to individualized electric field optimization.Method: We optimize montage across various populations, balancing the trade-off between focality and electric field strength at deep brain targets. The method is compared to conventional individualized electric field-based optimization. Key factors such as population size and population age were analyzed for their impact on montage selection and effectiveness.Results: Population-based electric field optimization demonstrated comparable focality and targeting accuracy to individualized analysis, with a difference of approximately 20%. The choice of the population proxy is an important factor to consider. Factors such as age mismatch or insufficient population size led to inconsistencies in montage optimization. For populations larger than 40 individuals, the impact of size on optimization outcomes was negligible.Conclusion: This study demonstrates the capability of population-based electric field analysis to achieve targeting effects comparable to individualized-level electric field analysis in terms of focality and intensity. By eliminating the need for patient-specific MRI scans, this approach significantly enhances the accessibility and practicality of tTIS in diverse research and clinical applications.