Double radiofrequency ablation is more extensive with a spherical zone shape compared to single ablation in a pig liver model

Objective: We compared the duration of ablation and the area of coagulation necrosis between a single ablation method (SAM) and a double ablation method (DAM) with a ’multitined expandable’ electrode (LeVeen 2cm) for radiofrequency ablation (RFA) using pig liver. Method: In the SAM group, ablation was completed after the first roll-off. In the DAM group, an additional ablation was performed to achieve a second roll-off. The comparison was made of the time required for roll-off and the extent of coagulation necrosis between the both groups. The Ellipticity index (EI) quantitatively describes the shape of the general RF ablation zone in the axial plane. Results: There was no statistically significant difference in the interval until the first roll-off between both groups (SAM group: 100.7±24.7 seconds vs DAM group: 103.2±37.7 seconds, P=0.43). In the DAM group, the interval from the start of the additional ablation until the second roll-off was 154.0±86.9 seconds, longer than the interval for the first roll-off (P=0.023). The extent of coagulation necrosis was significantly more extensive in the DAM group (axial diameter, mean±SD, 26.2±2.8mm)×(maximal diameter: 29.3±1.6mm)×(minimal diameter: 26.5±3.6mm) compared to the SAM group with (23.0±3.3mm)×(23.7±3.1mm)×(20.0±2.5mm), respectively. Although there was no statistically significant difference in the EI between both groups, macroscopically, the shape of coagulation necrosis tended to be non-spherical in the SAM group and spherical in the DAM group. Conclusions: The DAM with a ’multitined expandable’ electrode was more extensive with a spherical zone shape compared to the SAM. J. Med. Invest. 54: 28-34, February, 2007