Radio frequency ablation in the rabbit lung using wet electrodes: Comparison of monopolar and dual bipolar electrode mode

Objective: To compare the effect of radio frequency ablation (RFA) on the dimensions of radio frequency coagulation necrosis in a rabbit lung using a wet electrode in monopolar mode with that in dual electrode bipolar mode at different infusion rates (15 mm/hr versus 30 ml/hr) and saline concentrations (0.9% normal versus 5.8% hypertonic saline) . Materials and Methods: Fifty ablation zones (one ablation zone in each rabbit) were produced in 50 rabbits using one or two 16-guage wet electrodes with a 1-cm active tip. The RFA system used in the monopolar and dual electrode wet bipolar RFA consisted of a 375-kHz generator (Elektrotom HiTT 106, Berchtold, Medizinelektronik, Germany). The power used was 30 watts and the exposure time was 5 minutes. The rabbits were assigned to one of five groups. Group A (n = 10) was infused with 0.9% NaCl used at a rate of 30 ml/hr in a monopolar mode. Groups B (n = 10) and C (n = 10) were infused with 0.9% NaCl at a rate of 15 and 30 ml/hr, respectively in dual electrode bipolar mode; groups D (n = 10) and E (n = 10) were infused with 5.8% NaCl at a rate of 15 and 30 ml/hr, respectively in a dual electrode bipolar mode. The dimensions of the ablation zones in the gross specimens from the groups were compared using one-way analysis of variance by means of the Scheffe test (post-hoc testing). Results: The mean largest diameter of the ablation zones was larger in dual electrode bipolar mode (30.9 4.4 mm) than in monopolar mode (22.5 3.5 mm). The mean smallest diameter of the ablation zones was larger in dual electrode bipolar mode (22.3 2.5 mm) than in monopolar mode (19.5 3.5 mm). There were significant differences in the largest and smallest dimension between the monopolar (group A) and dual electrode wet bipolar mode (groups B-E). In dual electrode bipolar mode, the mean largest diameter of the ablation zones was larger at an infusion rate of 15 ml/hr (34.2 4.0 mm) than at 30 ml/hr (27.6 0.1 mm), and the mean smallest diameter of the ablation zones was larger at an infusion rate of 15 ml/hr (27.2 7.5 mm) than at an infusion rate of 30 ml/hr (24 2.9 mm). Conclusion: Using a wet electrode, dual electrode bipolar RFA can create a larger ablation zone more efficiently than monopolar RFA.