Effect of Electrode Contact Geometry on Shape of Coagulation Zone during SEEG-Guided Radiofrequency Thermocoagulation for Epilepsy Treatment

OBJECTIVE: Radiofrequency thermocoagulation (RF-TC) can be used to treat drug-resistant epilepsy during stereoelectroencephalography (SEEG) by implanting electrodes to create thermal lesions, although the optimal parameters and lesion strategies remain unclear. This study used computational modeling to analyze the influence of different electrode contact geometries on the shape of the coagulation zone. METHOD: The computational model simulated parallel SEEG electrodes with hemispherical and cylindrical contacts at various distances from each other. RF-TC was applied at 5 W for up to 30 seconds using clinical electrode geometry. Temperature distribution was calculated by the Bioheat Equation and tissue damage by the Arrhenius model, assuming both homogeneous gray matter and inhomogeneous white-gray matter interfaces, with a CSF gap around the electrodes. RESULTS: The simulations showed that both the contact geometry and inter-electrode distance influence the shape and contiguity of RF-induced coagulation zones: keeping the inter-electrode distance short appears to be important to promote overlapping of the coagulation zones and avoid the formation of separate lesions, although it also seriously restricts RF power deposition, resulting in overheating and impedance roll-off. A higher temperature is reached around the distal contacts, which undoubtedly favors roll-off when these are activated. CONCLUSIONS: As the contact geometry and inter-electrode distance influence the shape and continuity of RF-induced coagulation zones, these factors should be considered during procedural planning.