Syntheses of 18F-labeled pyrimidines and their usefulness for tumor imaging

18F-Labeled 5-fluorouracil(FUra), 5-fluoro-2'-deoxyuridine(FdUrd) and 5-fluorouridine(FUrd) were synthesized with high radiochemical purities. Biodistribution of the 18F-pyrimidines in tumor-bearing rats, mice or a rabbit was examined. Blood clearance of the 18F-pyrimidines was very rapid. The kidney and liver showed the high uptake and rapid clearance which was due to the metabolism and excretion. The 18F-concentration in the tumor was due to the metabolism and excretion. The 18F-concentration in the tumor was also high and clearance was very slow compared with those in other organs. Tumor uptakes of 18F-FdUrd were also shown by positron emission tomography and autoradiography. Biodistributions of the 18F-FdUrd and radio-deoxythymidine(dThd) were different between several organs, but similar distribution patterns in the tumor were observed by autoradiography.