Effects of superconducting knife diameter and freezing time of Endocare CryocareTM Surgical System on frozen necrosis area and histopathological changes of normal canine brain

Objective To investigate the effects of the variables of superconducting knife diameter and freezing time of Endocare CryocareTM surgical system on the necrosis extent and micro-pathological changes of the normal frozen brain tissue of dogs. Methods Argon-helium refrigeration superconducting knives of 2 and 3mm in diameter were respectively inserted into the right frontal lobe of dog brains, and the brains were frozen for 3 and 5min, respectively. The procedure was repeated one time. 48h later, the brains were perfused and harvested for the pathological observation under light microscope and electron microscope and the determination of necrosis area. Results 48h after refrigeration, the frozen brains presented hemorrhagic necrosis and were obviously divided into the central necrosis, inflammatory reaction zone, bleeding and edema zone. The boundaries were clear. Survival of brain cell structure was not found in the edge of frozen area. Conclusion Two freeze-thaw cycles with the freezing time of 3 and 5min are enough to cause the death of frozen brain tissue. Key words: Argon-helium knife;  Brain tissue;  Histology;  Pathology