Electromagnetic interference suppression in combined tACS-rTMS therapy

Objective. The therapeutic potential of phase-synchronized repetitive transcranial magnetic stimulation (rTMS) and transcranial alternating current stimulation (tACS) integration is hindered by uncharacterized electromagnetic interference.Approach. Through computational modeling and experimental validation using 3D-printed head phantoms, we identify three interference determinants and establish a multimodal suppression framework.Results. The maximum interference occurs when the coil is located directly above the F3 electrode of F3-FP2 tACS loop in natural sag state. Lead geometry optimization through twisted configurations reduced interference voltages by 20.06%, peaking at 91.92% suppression when orthogonal coil alignment (90°) minimized loop areas. Spatial analysis demonstrated a clear distance-dependent attenuation pattern, with interference levels decreasing to 94.05% when relocating the coil to posterior regions. Integrated low-pass filtering further eliminated high-frequency interference in F3-targeted TMS applications.Significance. These findings resolve the fundamental electromagnetic coupling challenge in combined tACS-rTMS systems, establishing the first clinically actionable protocol for concurrent operation.