Abstract
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Objectives [18F]FDG has been the most widely used radiotracer for PET studies in neuroscience, cardiology, and oncology. Positron-emitter labeled nucleosides also have been synthesized and used for measuring cell proliferation and monitoring the responses of cancer therapy (1). The aim of this study was to compare [18F]FDG, [18F]FLT, 5-[18F]FCdR (2) and 5-[18F]FUdR (3) (Fig. 1) as tumor imaging agents in LL2-tumor bearing mice.
Methods [18F]FDG, [18F]FLT, 5-[18F]FUdR and 5-[18F]FCdR were synthesized by the reported methods using FastLab, TRACERlab FN and TRACERlab FXFE modules. C57BL/6 mice were implanted subcutaneously into the right leg with LL2 cells. Seven days after implantation, the tumor uptake and whole-body biodistribution of all tracers in LL2-tumor bearing mice were performed for 1.5 hr using an Argus PET/CT scanner. Volumes of interest were defined on co-registrated PET/CT images using PMOD, and the time-activity curves of these tracers in various organs were expressed as SUV.
Results In contrast to [18F]FDG which has high accumulation of radioactivity in bladder, PET studies in LL2-tumor bearing mice showed that the radioactivity of these three 18F-labelled nucleosides accumulated mainly in the kidney and bladder. The tumor-to-muscle ratios of [18F]FDG, [18F]FLT, 5-[18F]FUdR and 5-[18F]FCdR in LL2-tumor bearing mice were 8.6±0.4 , 1.8±0.3, 4.5±0.5 and 4.7±0.5 (n=3 ), respectively.
Conclusions In addition to [18F]FDG, PET studies in mice showed that 5-[18F]FUdR and 5-[18F]FCdR were superior to [18F]FLT for visualization of LL2-tumor in mice. The utility of these tracers for imaging other tumors are under investigations.