Evaluation of the In Vivo Efficiency and Safety of Hepatic Radiofrequency Ablation Using a 15-G Octopus in Pig Liver

Objective: To determine in vivo efficacy of radiofrequency ablation (RFA) in porcine liver by using 15-gauge Octopus$^{(R)}$ (15-G Octopus$^{(R)}$) electrodes to create a large coagulation. Materials and Methods: A total of 18 coagulations were created by using a 180-W generator and 15-G Octopus$^{(R)}$ electrodes during laparotomy, performed in 14 pigs. Coagulation necrosis was created in the pig livers by the use of one of three RFA protocols: 1) group A, monopolar RFA using a 15-G Octopus$^{(R)}$ electrode with a 5-mm inter-electrode distance (n = 4); 2) group B, monopolar RFA using a 15-G Octopus$^{(R)}$ electrode with a 10-mm inter-electrode distance (n = 6); and 3) group C, switching monopolar RFA using two 15-G Octopus$^{(R)}$ electrodes (n = 8). The energy efficiency, shape, maximum and minimum diameters (Dmx and Dmi), and the volume of the coagulation volume were measured in each group. The Summary statistics were obtained and Mann-Whitney test was were performed. Results: The mean ablated volume of each group was 49.23 $cm^3$ in A, 64.11 $cm^3$ in B, and 72.35 $cm^3$ in C. The mean Dmx and Dmi values were 5.68 cm and 4.58 cm in A and 5.97 cm and 4.97 cm in B, respectively. In group C, the mean diameters of Dmx and Dmi were 6.80 cm and 5.11 cm, respectively. The mean ratios of Dmi/Dmx were 1.25, 1.20, and 1.35 in groups A, B, and C, respectively. There was one animal death during the RFA procedure, the cause of which could not be subsequently determined. However, there were no other significant, procedure-related complications during the seven-hourdelayed CT scans. Conclusion: RFA procedures using 15-G Octopus$^{(R)}$ electrodes are useful and safe for creating a large ablation in a single electrode model as well as in the multiple electrodes model.