Radiofrequency liver ablation: Experimental comparative study of water-cooled versus expandable systems

OBJECTIVE. We evaluate the uniformity and reproducibility of thermal lesion ablation and quantify the volume of tissue destruction and hemorrhage indu ced with two different commercially available radiofrequency ablation devic es. MATERIALS AND METHODS. A four-array anchor expandable needle electrode and a triple-cluster cooled-tip needle electrode were used to induce lesions in three explanted calf livers and in vivo in eight swine livers. The sizes o f the radiofrequency-induced lesions were macroscopically evaluated by meas uring two perpendicular dimensions immediately after the experiment. Bleedi ng was evaluated by weighing gauze swabs used to dry the hemorrhage caused by electrode insertions. RESULTS. In explanted liver, the mean diameter of the radiofrequency-induce d lesion was 5.3 +/- 0.7 cm for the cooled-tip needle and 3.7 +/- 0.4 cm fo r the expandable needle (p = 0.042), which correspond to approximate volume s of 65.35 +/- 26.22 cm(3) and 26.67 +/- 9.59 cm(3), respectively (p < 0.00 2). In vivo, the mean diameter was 3.7 +/- 0.4 cm for the cooled-tip needle and 3 +/- 0.4 cm for the expandable needle (p < 0.0001), which correspond to approximate volumes of 24.18 +/- 7.56 cm(3) and 11.16 +/- 3.65 cm(3), re spectively (p < 0.0001). Blood loss attained a median value of 3.5 g for th e cooled-tip needle and 2.6 g for the expandable needle; this difference wa s not statistically significant (p = 0.06). CONCLUSION. The cooled-tip needle induced significantly larger lesions than the expandable needle, but the lesions produced by the expandable needle a re more reproducible, uniform, and spheric. The larger size of the lesions produced by the coaled-tip needle may be attributed to the higher maximum p ower used by the generator and the higher energy deposition, which is due t o the cooling of the needle electrode.