Figure 2b. Mechanism of radio-frequency ablation. (a) Schematic depicts a four-prong needle electrode in which an alternating electric current at 460 KHz has caused ionic agitation around the electrode tip. (b) Schematic illustrates the ionic agitation, which causes frictional heat immediately around the needle. (c) Schematic shows how the heat caused by the agitation expands by conduction into the surrounding tissues to form a roughly spherical thermal injury.