Radiofrequency Tissue Ablation with Cooled-Tip Electrodes:An Experimental Study in a Bovine Liver Model on Variables Influencing Lesion Size

Han, Hyun Young; Lee, Jeong Min; Kim, Chong Soo

Abstract

PURPOSE: The purpose of this study was to determine the influence of various factors on the extent of thermal coagulation necrosis after radiofrequency (RF) tissue ablation using a cooled-tip electrode in bovine liver.
MATERIALS AND METHODS
RF ablation was induced by a monopolar 500 KHz-RF generator (CC-1; Radionics,Burlington, Mass., U.S.A.) and an 18-G cooled-tip with single or clustered electrodes. The ablation protocol involveda combination of varying current, ablation time, power output, gradual or abrupt increase of this out-put, and pulsed radiofrequency techniques. The maximum diameter of all thermal lesions which showed a color change was measured perpendicular to the electrode axis by two observers who reached their decisions by consensus. Twenty representative lesions were pathologically examined.
RESULTS
With increasing current lesion diameter also increased, but above 1500 mA no further increase was induced. Extending the ablation time to 9 minutes for a single electrode and 15 minutes for a clustered electrode increased lesion diameter until a steady state was reached. Higher power levels caused larger lesions, but above 100 W no increase was observed. Ample exposure time coupled with a stepwise increase in power level induced a lesion larger than that resulting from an abrupt increase. Continuous pulsed RF with a high current led to increased coagulation necrosis diameter.
CONCLUSION
These experimental findings may be useful thermotherapy. The data suggest that all involved factors significantly affect lesion size: if the factors are better understood, cancer thermotherapy can be better controlled.