Newly designed flexible electrode for laparoscopic radiofrequency ablation: Ex vivo and in vivo comparative studies with needle electrode in a porcine liver as technical study

Background: To compare the efficiency of radiofrequency ablation (RFA) using the newly designed flexible laparoscopic radiofrequency electrode and the internally cooled needle electrode for creating an ablation zone in ex vivo and in vivo porcine livers. Materials and Methods: In the ex vivo ablation zone, 40 ablation areas were created using the flexible electrode (group A, n = 5) and the needle electrode of the Cool-tip RF system (group B, n = 5). These were done in an excised porcine liver with a 200 W generator. In each group, ablation durations were 3, 6, 9, and 12 min, respectively. The volume was compared in each group. In the in vivo ablation zone, under laparoscopy, we divided the surface of the porcine liver into four areas: anterior, cranial, right lateral, and caudal. At each area, a couple of RFA using the flexible and needle electrodes with 6 min ablation duration was performed, respectively, in line with 3 cm intervals in five porcine livers. A flexible electrode was administered in the peritoneal cavity via a laparoscopic cannula, and a needle electrode was administered via a transcutaneous route, which avoided a pulmonary injury. The volumes and shapes of the ablation zones in each group and area were compared in the excised liver. Results: In the ex vivo experiments, the ablation volumes using the flexible and needle electrodes with 3, 6, 9, and 12 min ablation duration were 3.19 ± 0.41 cm³, 6.36 ± 0.48 cm³, 7.66 ± 0.51 cm³, 8.72 ± 0.78 cm ³ (Group A) and 3.40 ± 0.35 cm³, 6.83 ± 0.66 cm³, 7.79 ± 0.56 cm³, 8.85 ± 0.54 cm ³ (Group B). There was no statistical significance among all the ablated volumes in each group at the same duration. In the in vivo experiment, the differences in the short diameter and the volume of ablated zones in the caudal and right lateral areas were statistically significant (P < 0.05). In the cranial, right lateral, and caudal areas, the shape of the ablated zone using the needle electrode was elliptical. However, the ablated zone using the flexible electrode was spherical. The difference of the long and short diameter ratio in the cranial and right lateral areas was statistically significant (P < 0.05). Conclusion: The newly designed flexible laparoscopic RF electrode shows similar efficacies compared with the needle electrode in the ex vivo study. However, it shows superiority in efficacy and predictability with the increased volume and predictable shape of coagulation necrosis at the laparoscopic RFA in the porcine liver.