Pulmonary Cryoablation Zones: More Aggressive Ablation Is Warranted In Vivo

OBJECTIVE: The objective of our study was to determine the effective cryoablation zone when treating pulmonary tumors in vivo and to create pulmonary-specific ablation maps to guide clinical procedure planning. MATERIALS AND METHODS: Ablation volume was measured retrospectively in human patients after pulmonary tumor cryoablation with a triple-freeze protocol. Single-probe ablations were performed with 17-, 14-, and 13-gauge cryoprobes; multiple-probe ablations were performed with two or three 17-gauge probes. Statistical comparisons of ablation volumes to manufacturer reference values were calculated using the Wilcoxon rank-sum test. Comparisons of ablation sizes by the number of probes were evaluated by the Kruskal-Wallis test. RESULTS: increase per additional probe. The increased ablation zone size was more attributable to increased short-axis width (9.6-mm increase per probe) compared with long-axis length (5.6-mm increase per probe). CONCLUSION: The in vivo effective pulmonary cryoablation zone is significantly smaller than the manufacturer-published in vitro isotherm. Larger ablation margins in lung are best achieved by using multiple cryoprobes.