No-touch Radiofrequency Ablation using Multiple Electrodes: Comparative studies of Switching Monopolar versus Switching Bipolar Modes

Abstract

Introduction: To evaluate the technical feasibility, efficiency, and safety of switching bipolar (SB) and switching monopolar (SM) radiofrequency ablation (RFA) for no-touch ablation technique Methods: Ex vivo and in vivo study were performed separately. In ex vivo study, A pork loin cube was inserted as a tumor mimicker in the bovine liver block

RFA was performed using the no-touch technique in the SM mode (2 groups, A1: 10 minutes, n = 10

A2: 15 minutes, n = 10) and SB mode (1 group, B: 10 minutes, n = 10). In in vivo study approved by the animal care and use committee of the Institute, RFA was performed on 2 cm tumor mimickers in the liver using a no-touch technique in the SM mode (2 groups, SM1: 10 minutes, n = 10

SM2: 15 minutes, n = 10) and SB mode(1 group, SB: 10 minutes, n = 10). The groups were compared technical success which was based on the creation of confluent necrosis with sufficient safety margins, and the ablation size, and the distance between the electrode and ablation zone margin (DEM). To evaluate safety, small bowel loops were placed above the liver surface and 30 additional ablations were performed in the same groups of ex vivo study. Moreover in in vivo study, thermal injury to the adjacent anatomic organs were compared between SM-RFA (15 minutes, n=13) and SB-RFA modes (10 minutes, n=13). Results: The technical success rate of the creation of confluent necrosis was higher in the group SB than group SM1 (both p<0.05) although confluent necrosis with sufficient safety margins were created in all specimens of ex vivo study. Gross ablation volume and DEM in SB-RFA mode was smaller than that in SM-RFA for 15 min ablation in both ex vivo and in vivo studies (both p < 0.05). The incidence of thermal injury to the adjacent organs and tissues was significantly less in the SB-RFA mode than that in SM-RFA mode (p=0.001 and p=0.021 in ex vivo and in vivo studies, respectively). Conclusions: SB-RFA was more feasible for no-touch technique of liver tumors with a better safety profile than the SM-RFA.