Evaluation of [18F]Fluoroethyl-L-tyrosine and [18F]FDG as PET tracer for brain tumor imaging

  • Mr Shih-Yen Wu, Institute of Radiological Sciences, National Yang-Ming University, Taipei, Taiwan, Taiwan
  • Prof Hsin-Ell Wang, Institute of Radiological Sciences, National Yang-Ming University, Taipei, Taiwan, Taiwan
  • Dr Wen-Sheng Huang, Department of Nuclear Medicine, Tri-service General Hospital, National Defense Medical Center, Taipei, Taiwan, Taiwan
  • Dr Cheng-Yi Cheng, Department of Nuclear Medicine, Tri-service General Hospital, National Defense Medical Center, Taipei, Taiwan, Taiwan
  • Dr Daniel Shen, Department of Nuclear Medicine, Tri-service General Hospital, National Defense Medical Center, Taipei, Taiwan, Taiwan
  • Dr Chih-Yung Chang, Department of Nuclear Medicine, Tri-service General Hospital, National Defense Medical Center, Taipei, Taiwan, Taiwan

    • Objective: 2-Deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) positron emission tomography (PET) has been extensively used in clinical tumor imaging. However, the high uptake of [18F]FDG in brain, heart and inflammatory lesions may result in false-positive findings. Other than the increased demand of glycolysis, amino acid transport as well as protein metabolism are more active in tumor cells, while the uptake of amino acids in normal tissues is usually lower. This study compared the pharmacokinetics of O-2-[18F]fluoroethyl-L-tyrosine (L-[18F]FET) to that of [18F]FDG in an animal brain tumor model.

    Methods: N-BOC-(O-(2-tosyloxyethyl))-L-tyr-OBzl was used to produce no-carrier-added L-[18F]FET. The cellular uptake, biodistribution, autoradiography and microPET imaging of L-[18F]FET and [18F]FDG were performed with F98 glioma cell culture and F98 glioma-bearing Fischer344 rats.

    Results: The uptake of L-[18F]FET in the F98 glioma cells increased rapidly for the first 5 min and reached a steady-state level after 10 min of incubation, whereas the cellular uptake of [18F]FDG kept increasing during the study period. The biodistribution of L-[18F]FET and [18F]FDG in the brain tumors was 1.21 ± 0.25 and 2.68 ± 0.41 %ID/g at 60 min post injection, respectively, while the tumor-to-normal brain uptake ratios of L-[18F]FET (3.23) were higher than that of [18F]FDG (1.38). MicroPET images of L-[18F]FET exhibited remarkable uptake with high contrast in the brain tumor, whereas [18F]FDG showed high uptake in the normal brain and gave blurred brain tumor images.

    Conclusion: L-[18F]FET PET has higher tumor-to-normal brain uptake ratios than F-18 FDG PET and is suitable for the brain tumor imaging as shown in this study.