Multiple-Electrode Radiofrequency Ablation of In Vivo Porcine Liver: Comparative Studies of Consecutive Monopolar, Switching Monopolar Versus Multipolar Modes

Purpose:To evaluate the in vivo efficiency of 2 multiple-electrode radiofrequency (RF) systems to create confluent areas of coagulation in porcine liver, compared with consecutive overlapping ablation. Materials and Methods:A total of 18 coagulations were created with 3 RF devices and 3 internally cooled electrodes at laparotomy in 6 female pigs. RF was applied to the porcine livers in a consecutive, monopolar mode (group A), in a switching monopolar mode (group B), or in a multipolar mode (group C). Energy efficiency values for the RF systems, shape and dimensions, and the coefficients of variation of the coagulation zones were compared in the 3 groups. Results:The duration of the RF ablation procedures in groups A, B, and C were 36 minutes, 18 minutes, and 21.2 ± 1.9 minutes. The average energy delivered to produce 1 cm3 coagulation was greater in group A (5.6 ± 2.3 kJ/cm3) than in group B (1.8 ± 0.5 kJ/cm3) or in group C (2.0 ± 0.8 kJ/cm3) (P < 0.05). The mean volumes of the coagulations in groups A, B, and C were 28.8 ± 13.2 cm3 in group A, 49.1 ± 12.3 cm3 in group B, and 40.6 ± 16.3 cm3 in group C, respectively (P = 0.07). Regarding the shape of the coagulations, the coagulations of groups B (isoperimetric ratio; 0.88) and C (0.84) were more spherical than those of group A (0.69) (P < 0.05). In addition, the coefficients of variation of the volumes of the ablation zones in groups A, B, and C were 0.46, 0.25, and 0.40, respectively. Conclusions:Multiple-electrode RF systems in switching monopolar and multipolar modes more efficiently created a larger, confluent, spherical-shaped coagulation than conventional consecutive RF ablation.

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