PURPOSE: To determine with comparison of two different monopolar radiofrequency (RF) devices whether a longer duration of energy application has an effect on coagulation necrosis in ex vivo bovine liver tissue.

MATERIALS AND METHODS: The volume and short- and long-axis diameters of the coagulation were assessed in ex vivo bovine livers after RF application for 5-60 minutes. A power of 60 W was used for the single perfusion applicator (n = 48), and a power of 200 W was used for the internally cooled cluster applicator (n = 48). Reproducibility and coagulation shape were assessed and compared. For statistical evaluation, the mean values of the dimensions were compared by using analysis of variance with the following factors: applicator, RF duration, and their interaction.

RESULTS: RF application up to 60 minutes produced a mean maximum volume of coagulation of 116.8 cm(3)(95% confidence interval [CI]: 98.4 cm(3), 138.8 cm(3)) for the single perfusion device and 89.5 cm(3)(95% CI: 75.4 cm(3), 106.3 cm(3)) for the internally cooled cluster applicator. For both devices, duration of energy application up to 60 minutes showed a significant interaction for the volume and the short- and long-axis diameters of coagulation (P < .0001). The volumes of coagulation necrosis induced with the internally cooled cluster applicator were more reproducible than those induced with the single perfusion applicator (P < .0001). The shape of the lesion was closer to a sphere (mean shape ratio, 0.98) for the internally cooled cluster than for the single perfusion applicator (mean shape ratio, 1.21) (P < .0001).

CONCLUSIONS: There is a significant interaction between RF duration and both RF devices influencing the dimensions of coagulation. Longer durations of energy application expand the volume of coagulation with a better reproducibility and more spherical shape of coagulation for the internally cooled cluster device.