In vivo efficiency of multipolar radiofrequency ablation with two bipolar electrodes: A comparative experimental study in pig kidney

PURPOSE: To compare in vivo efficacy of multipolar radiofrequency (RF) ablation with two internally cooled electrodes to that of monopolar RF ablation with internally cooled single and cluster needles to induce coagulation in in vivo porcine kidneys. MATERIALS AND METHODS: Twenty-four coagulations were created in the kidneys of 12 pigs by means of laparotomy by using a monopolar or multipolar RF system. In the monopolar mode, RF was applied to a single internally cooled probe (group A) or to a cluster probe (group B) for 12 minutes. In the multipolar mode, RF was applied to two bipolar probes with 2-cm interprobe spacing up to 50 kJ (group C). Technical parameters and the dimensions, shapes, and coefficients of variation of the coagulations were compared among the three groups. RESULTS: The minimum transverse diameters of the RF-induced coagulations in groups B (3.5 cm +/- 0.5) and C (3.8 cm +/- 0.6) were significantly larger than that in group A (2.6 cm +/- 0.3). The mean coagulation volumes produced in the multipolar group (25.1 cm(3) +/- 5.2) were greater than those produced in the monopolar groups (11.6 cm(3) +/- 3.7 and 18.1 cm(3) +/- 5.8) (P<.05). The mean ratio of transverse diameter to vertical diameter of the coagulations was larger in groups B and C (1.2 +/- 0.2 and 1.0 +/- 0.1, respectively) than in group A (0.8 +/- 0.2) (P<.05). In addition, the coefficients of variation for groups A, B, and C were 0.33, 0.30, and 0.21, respectively. The procedure time was longer with the multipolar technique (27.2 minutes +/- 4.9) than with the monopolar technique with a single or cluster probe (12 minutes). CONCLUSIONS: Multipolar RF ablation showed at least equivalent or better in vivo efficiency for creating a larger coagulation than monopolar RF ablation with single or cluster electrodes, but with a longer procedure time and at slightly greater complexity.