When electric current is applied to tissue, heating results due to resistive losses. is heating occurs independent of frequency of the current; at frequencies below ~10 kHz additional eects such

as stimulation of excitable tissue and electrochemical reactions (at DC) may occur. To avoid these eects, RF ablation-based heating employs higher frequencies in the range of 450-500 kHz (this particular range is also used because electrosurgical devices, which served as predicate devices, operate in the same frequency band). Figure 9.1 illustrates the setup of an RF ablation procedure, where an electrode is inserted into a target location in tissue to be destroyed. Materials used for RF electrodes include steel, platinum, and Ni-Ti alloys; parts of the RF electrode are typically electrically insulated (e.g., to avoid heating of the sha region). Ground pads (dispersive electrodes) are placed on the patient’s skin (oen thigh or back) to serve as a return path for the RF current.