3:10 PM Abstract No. 343 Determination of the cryoablation margin: in vivo swine experimentation in renal & hepatic tissue with histopathological assessment: comparison between an abbreviated single 15-minute freeze protocol to the conventional 10-8-10 minute freeze-thaw-freeze protocol

Abstract

To determine the frozen but non-lethal margin beyond the periphery of the ablation zone of a single 15 minute freeze protocol and compare it with that of the conventional 10 minute freeze, 8 minute active thaw, 10 minute freeze cycle (10-8-10) in swine liver and kidney. Additionally, the ablation zones were assessed for the presence of islands of viable tissue in both tissues after each protocol. Percutaneous CT-guided cryoablation was performed in 5 swine liver and kidney. In each organ, one ablation was performed utilizing the 10-8-10 minute cycle and a second utilizing the single 15 minute cycle. When the “ice-ball” was maximal, 10 cc of black India Ink was arterially infused into the organ. The two ablations were timed to end simultaneously such that the organs were stained at maximal ablation volume. Histologic analysis was performed by pathologist. The ablation length (long axis of the cryoprobe tract) and maximum width (perpendicular to the cryoprobe track) were measured and the tissues were fixed in formalin. 3 μm sections parallel to the cryoprobe tract were stained with H&E. Based on the India ink staining pattern, specimens were assessed for non-frozen tissue, ablated tissue, and ablation margin. Finally, the ablated region was examined for islands of viable tissue. The frozen, but non-lethal margin after cryoablation was found to be approximately 1 mm regardless of the cryoablation protocol performed or the type of tissue. Histopathologic examination of the ablated region showed no cellular viability in any of the tissue specimens, regardless of cryoablation protocol. An abbreviated, single 15-minute cryoablation resulted in an ablation margin identical to that of the conventional 10-8-10 minute protocol with uniform cell death and no islands of viable tissue remaining in both swine kidney and liver.