Feasibility of a Low-Power Radiofrequency Ablation Protocol to Delay Steam Popping.

ABSTRACT

PURPOSE: Steam popping frequently occurs during conventional high-power radiofrequency (RF) ablation, increasing the risk of tumor spread. The aim of this study was to evaluate the effect of a low-power RF ablation protocol on the intensity and timing of steam popping in ex vivo bovine liver. MATERIALS AND METHODS: High-power (maximum 200 W; group 1) and low-power (maximum 70 W; group 2) RF ablation protocols were established. In the first phase, RF ablation was conducted for 12 min. Ablation volume, intensity, and timing of maximal popping sounds and total energy generated for RF ablation were compared between groups 1 and 2. In the second phase, RF ablation was conducted until maximal popping occurred, and ablation zones on histologic specimens were compared. RESULTS: Relative to group 1, maximal popping occurred at significantly delayed timing in group 2 (50 s ± 11 vs 397 s ± 117; P < .001), but without a difference in intensity (ratios vs reference sound of 0.70 ± 0.18 vs 0.83 ± 0.26; P = .138). The ablation volume after 12 min of RF ablation did not differ between groups 1 and 2 (18.46 cm(3) ± 1.35 vs 15.78 cm(3) ± 0.64; P = .086). However, in the histologic specimens obtained when maximal popping occurred, the area of complete coagulative necrosis was significantly larger in group 2 (P < .05). CONCLUSIONS: Low-power RF ablation delays steam popping while providing comparable therapeutic effects to high-power RF ablation. Delaying maximal popping may prevent tumor cell dispersion because maximal popping occurs after an adequate ablation zone has been achieved.