18F-FDG PET for Semiquantitative Evaluation of Acute Allograft Rejection and Immunosuppressive Therapy Efficacy in Rat Models of Liver Transplantation

Acute allograft rejection remains a major complication after liver transplantation. We report a semiquantitative imaging method of detecting acute allograft rejection with 18F-FDG PET. Methods: Syngeneic and allogeneic transplanted rats, with or without immunosuppressive treatment, were subjected to serial PET. Autoradiography of the liver was conducted in both the syngeneic and the allogeneic rats. Results: A significant increment of 18F-FDG accumulation in liver allografts was observed by PET on day 2. The 18F-FDG signal was concentrated in the area where inflammatory cells around the vessels were detected by autoradiography. Allotransplanted rats treated with an immunosuppressive agent displayed a marked decrease in hepatic 18F-FDG uptake, compared with allotransplanted rats that were not treated. Conclusion:18F-FDG PET may be a valid method for facilitating the development of protocols to diagnose graft rejection and to monitor the efficacy of immunosuppressive therapy.