Thesis (M.Sc.)--Chulalongkorn University, 2007

Objective: To compare the efficiency of multiple electrodes radiofrequency ablation (RFA) combined with electrode replacements between switching multipolar and switching bipolar methods for creating an ablation area in ex vivo porcine livers. Materials and Methods: We used a 330 kHz RF generator and three perfused needle electrodes to create 50 ablation zones by performing switching multipolar RFA (n = 25) or switching bipolar RFA (n = 25) in explanted porcine livers. In both methods, ablation areas were created by applying radiofrequency (RF) energy to the perfused needle electrodes in three sessions for 12, 10 and 8 minutes, respectively (total time = 30 minutes). The changes in the current, power output, voltage output and liver temperature during RFA, as well as the diameters, volume and shape of the thermal ablation zones, were compared between the two groups. Results: In the switching multipolar and switching bipolar groups, the mean final-temperature values were 74.92 +- 7.41 degrees celsius and 70.92 +- 8.82 degrees celsius, respectively (p = 0.089). The switching multipolar mode created a larger volume of ablation than did the switching bipolar mode: 156.51 +- 26.81 cm[superscript 3] and 125.49 +- 29.72 cm[superscript 3], respectively (p < 0.000). Conclusion: For the multiple electrodes RFA, the switching multipolar method was more efficient in generating larger areas of thermal ablation than the switching bipolar method.