Comparison of dual- and triple-freeze protocols for hepatic cryoablation in a Tibet pig model.

The purpose of this study was to compare a dual-freeze protocol with a triple-freeze protocol for hepatic cryoablation in a porcine model. Eighteen cryoablations were performed over an exposed operation field in nine normal porcine livers, using dual- (10-5-10-5) and triple-freeze (5-5-5-5-10-5) protocols. Changes in the temperature of the cryoprobes and the diameter of the iceballs were recorded during the ablation, and pathological changes in the cryozones (zones of tissue destruction) were assessed seven days after the procedure. Use of two and three freeze-thaw cycles produced iceballs of different diameters. Seven days after cryosurgery, the triple-freeze protocol was associated with a larger zone of complete necrosis than the dual-freeze protocol, although the two protocols produced cryozones and cryolesions of similar length, and in both cases the cryozones contained five areas of destruction. With the same freezing time (20 min), the triple-freeze protocol may be a more powerful liver ablation method than the dual-freeze protocol.