Newly designed flexible electrode for laparoscopic radiofrequency ablation: Ex Vivo and In Vivo comparative studies with needle electrode in porcine livers

Abstract

[한글]

[영문]

To overcome the limitation of laparoscopic radiofrequency ablation (RFA) in lesions located liver dome or inferior surface of liver, a flexible laparoscopic radiofrequency electrode with 2 cm of exposed metallic tip was designed and constructed. For the ex vivo study, forty ablation areas were created using the flexible electrode (group A, n = 5) or the needle electrode of Cool tip RF system (group B, n = 5) in excised porcine liver with a 200 W generator. In each group, the durations of ablation were 3, 6, 9 and 12 min respectively. The ablation volume was compared in each group. For the in vivo study, the surface of porcine liver was divided into four areas; anterior, cranial, right lateral, and caudal. At each area, a couple of RFA using the flexible and needle electrode with 6 min ablation was done under laparoscopy, respectively with 3 cm interval in five porcine livers. The flexible electrode was administered in the peritoneal cavity via laparoscopic cannula, and the needle electrode was administered via percutaneous route to avoid pulmonary injury. The volumes and shapes of the ablation zone in each group and area were compared in the excised liver. For the evaluation of histological changes and safety, RFA was performed to three female adult pigs as same as prior in vivo experiment described above. The pigs were scarified immediately, 1 week and 2 weeks after ablation respectively. Microscopic findings were observed and compared between the groups about changes of ablated lesion according to the flow time after RFA. In the ex vivo experiment, the ablation volumes using the flexible and needle electrode with 3, 6, 9 and 12 min ablation were 3.19 ± .41 cm3, 6.36 ± .48 cm3, 7.66 ± .51 cm3, 8.72 ± .78 cm3 (Group A) and 3.40 ± .35 cm3, 6.83 ± .66 cm3, 7.79 ± .56 cm3, 8.85 ± .54 cm3 (Group B), respectively. There were no statistical significances between all the ablated volumes in each group at the same duration. In the in vivo experiment, the difference of the short diameter and the volume of ablated zones in caudal and right lateral area showed statistical significance (p < .05). In cranial area, right lateral and caudal area, the shape of the ablated zone using the needle electrode was elliptical, but that using the flexible electrode was spherical. However, the difference of long and short diameter ratio in cranial and right lateral area was statistically significant (p < .05). In the safety study, all three pigs showed no complication during the 2 wks follow up. In histological evaluation, core necrosis with surrounding swelling and hemorrhage at the immediate follow up and it was changed to the widening of necrosis and peripheral fibrosis at 2 wks follow up. There was no deference in the histological findings between flexible and needle electrode. The newly designed flexible laparoscopic RF electrode shows similar efficacies compared with the needle electrode in ex vivo study. However, it makes the superiority in efficacies and predictability with the increased volume and predictable shape of coagulation necrosis at the laparoscopic RFA in the porcine liver in vivo.