Switching bipolar hepatic radiofrequency ablation using internally cooled wet electrodes: comparison with consecutive monopolar and switching monopolar modes

Objective: To evaluate whether switching bipolar radio-frequency ablation (SB-RFA) using three internally cooled wet (ICW) electrodes can induce coagulations >5cm in porcine livers with better efficiency than consecutive monopolar (CM) or switching monopolar (SM) modes. Methods: A total of 60 coagulations were made in 15 in vivo porcine livers using three 17-gauge ICW electrodes and a multichannel radiofrequency (RF) generator. RF energy (approximately 200W) was applied in CM mode (Group A, n=20) for 24min, SM mode for 12min (Group B, n=20) or switching bipolar (SB) mode for 12min (Group C, n=20) in in vivo porcine livers. Thereafter, the delivered RFA energy, as well as the shape and dimension of coagulations were compared among the groups. Results: Spherical-or oval-shaped ablations were created in 30% (6/20), 85% (17/20) and 90% (18/20) of coagulations in the CM, SM and SB groups, respectively (p=0.003). SB-RFA created ablations >5cm in minimum diameter (D-min) in 65% (13/20) of porcine livers, whereas SM- or CM-RFA created ablations >5cm in only 25% (5/20) and 20% (4/20) of porcine livers, respectively (p=0.03). The mean D-min of coagulations was significantly larger in Group C than in Groups A and B (5.1 +/- 0.9, 3.9 +/- 1.2 and 4.4 +/- 1.0cm, respectively, p=0.002) at a lower delivered RF energy level (76.8 +/- 14.3, 120.9 +/- 24.5 and 114.2 +/- 18.3 kJ, respectively, p<0.001). Conclusion: SB-RFA using three ICW electrodes can create coagulations >5cm in diameter with better efficiency than do SM- or CM-RFA. Advances in knowledge: SB-RFA can create large, regular ablation zones with better time-energy efficiency than do CM- or SM-RFA.