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Purpose:The principal focus of the study was exploring the hyperacute responses with respect to normal liver and the change of assessment indexes for different observation times and radiation doses after total body X-irradiation exposures using Tibet mini-pig model.Methods and Materials:A total of 48 adult male Tibet mini-pigs were divided into six groups randomly.Five treatment groups(n=9)were irradiated with single dose of 2,5,8,11 and 14-Gy total body irradiation respectively using a 8Mv X-ray (isocenter)linear accelerator,and a dose rate of 255 cGy/min for each group.These pigs were tested by 2-[18F]Fluoro-2-deoxy-D-glucose positron emission tomography with computed tomography and hepatic zymological test,and then sacrificed by taking in carbon dioxide for pathologic test at 6,24 and 72 hours(each time n=3)after irradiation respectively.Results:Radiation doses had highly significant effects on all detecting indexes except CT values.Overall,the most obvious tendency appeared at 24 hours after TBI and the most obvious change happened at 5 or 8 Gy.Hepatic standard uptake values (SUV)showed the same tendency at relatively low doses(0-5 Gy)and the opposite tendency at relatively high doses(8-14 Gy)with pathology score and hepatocyte counting respectively;it showed the similar tendency with binucleated hepatocytes counting at 24 hours after TBI.Conclusion:(1)Normal liver was more sensitive than previous viewpoints and the hyperacute response of liver showed some regularity to radiation exposure.(2)5 Gy is a key dose.(3)[18F]-FDG-PET/CT had the potential to assess roughly the absorbed radiation dose,the conditions of metabolism and severity of liver injury after radiation exposure as a sensitive and noninvasive method.