Abstract
Abstract
Objective: The objective of this study was to characterize, for selected group-level optimized montages, electrode-specific dosimetric sensitivity to placement variability in transcranial alternating current stimulation (tACS) and transcranial temporal interference stimulation (tTIS).
Approach: Electric fields (EFs) were computed using the scalar-potential finite-difference (SPFD) method in 60 paired model instances generated from MRI data of 30 male participants (30 original models and their left–right mirrored counterparts). Three anatomically defined targets spanning cortical and subcortical structures were examined: the primary somatosensory hand area (S1 Hand), the insula, and the hippocampus. Every electrode constituting each selected montage was independently displaced from −10 mm to +10 mm in 5 mm increments on a 5 × 5 tangential grid. Three descriptive outcomes were evaluated: intensity sensitivity, defined as the absolute percentage change in the region-of-interest (ROI) mean; hotspot displacement; and position-dependent intensity variability, defined as the standard deviation (SD) of the percentage change across the full ±10 mm grid.
Main results: Across all 16 displaced electrodes, intensity sensitivity ranged from 0.41% to 14.88%, and hotspot displacement ranged from 0.63 mm to 6.86 mm. Marked within-pair asymmetries were observed in several montages, and position-dependent intensity variability differed across electrodes and model instances. These patterns were descriptively associated with montage geometry and current allocation.
Significance: The independent all-electrode perturbation framework introduced here enables electrode-specific robustness assessment of group-level optimized tACS and tTIS montages. The results identify montage-specific electrodes for which placement control is particularly important within the studied configurations, informing the practical implementation of these montages.