Radiofrequency Ablation of the Porcine Liver In Vivo: Increased Coagulation with an Internally Cooled Perfusion Electrode

A major limitation of radiofrequency (RF) ablation is its inability to produce a large enough diameter of coagulation necrosis to encompass hepatic tumors with an appropriate ablative margin at a single RF application. We evaluated the in vivo efficiency of RF ablation (RFA) using an internally cooled perfusion (ICP) electrode with hypertonic saline infusion to induce coagulation necrosis compared with that of RFA using single needle electrode types. RF was applied to a porcine liver in monopolar mode using a 200 W generator and an internally cooled electrode (group A) or an ICP electrode (group B) at 200 W for 12 minutes or using a 60 W generator with a perfusion electrode at 40 W for 20 minutes (group C). In total, 36 (3 × 12) ablation zones were created using the three different regimens. In group B, 14.6% NaCl solution was infused at 1 mL/minute and in group C, 0.9% NaCl solution was infused at 1.5 mL/minute. The three groups were compared in terms of amount of delivered RF energy and dimensions and the coefficients of variation of the ablation zones. The mean energies applied in the three groups were 52.3 ± 10.3 kJ for group A, 115.4 ± 10.5 kJ for group B, and 38.5 ± 11.5 kJ for group C, respectively ( P < .05). The mean ablation volumes in groups A, B and C were 13.1 ± 4.7 cm 3 in group A, 43.7 ± 17.5 cm 3 in group B, and 26.3 ± 20.2 cm 3 in group C, respectively ( P < .05). In addition, the coefficients of variation of the volumes of the ablation zones in groups A, B, and C were 0.36, 0.4, and 0.78, respectively. RFA using the ICP electrode showed better performance in terms of creating a larger ablation zone than RFA using an internally cooled or a perfusion electrode.