3D finite element model of RF heating: novel nonablative cutaneous therapy

This study presents a finite element model of a non-ablative RF tissue heating system for dermatological applications. The Thermage ThermaCool TC System consists of a capacitively coupled treatment tip, handpiece, RF generator, and cryogen delivery system. Various electrode geometries were created to generate uniform thermal profiles at specific depths in the tissue. The optimal thermal treatment depth for a clinical indication is influenced by factors such as tissue thickness for a given anatomical location, the desired target for heating in that tissue, and anesthesia factors. Electrodes of ¼, 1, and 1½cm2 area were evaluated for depth of treatment. A 3D multi-physics finite element model was developed to simulate RF heating in tissue. The program coupled electrical and thermal models to predict the electric field produced and the consequent heating. The electrical portion of the model was verified using an electric field mapping system. The thermal section of the model was confirmed via thermocouple measurements for cooling and infrared imaging measurements for RF heating. The FEM model produced electrical and thermal predictions that were verified with experimental measurements. The finite element model shows significant potential as a predictive R&D tool to assist in RF electrode design and reduce product development time.