J.K.J.M. Lee, J.K. Han, B.W. Choi; Seoul/KR

Purpose
To evaluate the in vivo efficiency of radiofrequency (RF) ablation using an internally cooled-perfusion (ICP) electrode for inducing coagulation necrosis compared with those of RFA using internally cooled, or multitined expandable electrodes.

Material and methods
Using a 200W generator and internally cooled and ICP electrodes or a 150W generator and a multitined expandable electrode, a total of 15 RF ablations were performed in the kidneys of nine pigs. After placing an electrode in lower pole of a kidney, one ablation zone was created using one of three different regimens: Group A: RF ablation using an internally cooled electrode, Group B; RF ablation using an ICP electrode with 14.6% NaCl solution instillation at 1mL/min, Group C: RF ablation using a multitined expandable electrode. Three days after the procedures, contrast-enhanced CT scans were obtained to evaluate ablation region volumes, and kidneys were harvested for gross measurements. The three groups were compared with respect to technical parameters such as changes in impedance and current during RF ablation. The dimensions of thermal ablation zones created in the three groups were compared histologically.

Results
In vivo study showed that ICP electrode allowed a greater energy delivery than internally cooled or multitined expandable electrode during RF ablation, i.e., 63.3 ± 8.8 kJ in group A, 101 ± 3.3 kJ in group B and 61.8 ± 12.5 kJ (p < 0.05). In vivo studies showed RF ablation using ICP electrode achieved larger mean coagulation volumes than RF ablation using the other electrodes: 12.0 ± 3.9 cm3 in group A; 30.5 ± 7.6 cm3 in group B; 11.6 ± 6.7 cm3 (p<0.05). In addition, group B had a larger mean short-axis diameter of RF-induced coagulation necrosis than groups A or C: 2.6 ± 0.5 cm in group A; 3.6 ± 0.4 cm in group B; and 2.4 ± 0.7 cm in group C (the difference between groups B and C: p < 0.05).

Conclusion
RF ablation using an ICP electrode showed better performance at creating coagulation necrosis than RF ablation using internally cooled or multitined expandable electrodes in this porcine renal model.