| ObjectiveTo observe the appearance of US, MRI, pathology and the hemodynamic changes of the rabbit's artery after argon-helium cryoablation, to evaluate the influence of cryoablation for the rabbit's artery, then to provide the experimental evidence for the safety and feasibility of the treatment of tumors adjacent to blood vessels by cryoablation under imaging guided.Materials and methodsFifteen Normal New Zealand white rabbits were randomly divided intotwo groups, namely, experimental group, and control group. Twelve rabbitswere for experimental group, and three rabbits were for control group. In the experimental group, the rabbit's artery, which diameter is 3mm, was selected as target vessel. The procedures were performed under general an-esthetic. Cryoablation was performed using high-pressure argon system (Cryo-Hit sy-stem) under MRI guidance, and the cryoablation parameterswhich we used were a twice repeated freeze-thaw cycle,where 100%flow rate of argon gas was maintained to achieve freezing for 12 minutes and correspondingly helium gas was used to thaw for 5 min-utes. For demonstrating the ice ball and the target vessel, MRI was acqu-ired on 0.23T MR scanner during the procedure. The hemodynamics para-meters,which include the target vessel's diameter,velocity,resistent index,pulsatility index, and the imaging appearance of target vessels were acq-uired before cry-oablation and at the first day, the seventh day, the thir-tieth day,the ninetieth day after cryoablation. At the same time,three ra-bbits were sacrificed, and the specimens of target vessels were exam-ined for light microscopy, transmission electron microscope. The rabbits of control group withoutcryoablation only were sacrificed,and the specime-ns of target vessels wereexamined for light microscopy,transmission ele-ctron microscope.Results1. Intraoperative imaging appearance: The target vessels were all displayed flow void signal on T1WI during cryoablation. The size of ice ball was gradually increased. The size of ice ball was the biggest at 10 min after freezing, which was 2.5cm×5.0cm. The ice ball was all shown as oval-shaped low-signal areas. 2. CDFI and US appearance : There was no significant difference in the hemodynamics parameters for target vessels among precryoablation and the first day, the seventh day, the thirtieth day, the ninetieth day after cryoablation. There was no obvious abnormality on US appearances of target vessels at the first day, the seventh day, the thirtieth day, the ninetieth day after cryoablation. 3. The target vessels'histopathologic appearance after cryoablation: obviously artery injury was observed at the first day, the seventh day after argon-helium cryoablation. The endothelial cells were swollen or loss. The smooth muscle fibers in the media became swollen and refractory to stains and their nuclei became irregular and pyknotic, some necrosis of smooth muscles cells were observed. Beside local endothelial cells and smooth muscle cells slightly swollen, the other structures of the wall were repaired at the thirtieth day after cryoablation. These damages can be recoveried at the ninetieth day after cryoablation.Conclusions1.The characteristics of target vessels during the argon-helium cryoablation could be demonstrated by intraoperative MRI. 2. There were no significant changes in hemodynamic and imaging appearance for target vessels after argon-helium cryoablation under MRI guidance. 3. If the ice ball closed and / or wrapped the rabbit's artery (3mm diameter), the reversible damage could be occurred in endomembrane, tunica media and adventitia, and these damages could be repaired at the ninetieth day after Argon-helium cryoablation.
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