Distributed Equivalent-Circuit Models for Circular Dispersive Electrodes

Analytically solvable distributed equivalent-circuit models have been developed for circular electrosurgical dispersive electrodes which are either resistively or capacitively coupled to the body. Calculations based on these models show that for either electrode type it is possible to define a characteristic length, the magnitude of which governs the current distribution under the electrode. The well-known perimetrical burn problem occurs when the current transfer length is much smaller than the electrode radius: a problem which may arise with either capacitive or resistive electrodes. Design guidelines are given for the optimization of simple circular dispersive electrodes, and suggestions for further improvements are discussed.