¹⁸F-FDG, ¹⁸F-FET and ¹⁸F-FLT small animal PET imaging in orthotopic mouse brain tumor model

Objectives The aim of this study was to compare the glucose analog, 2-[¹⁸F]fluoro-2-deoxy-D-glucose (¹⁸F-FDG), the amino acid analog, o-(2-[¹⁸F]fluoroethyl)-L-tyrosine (¹⁸F-FET) and nucleoside analog, 3′-[¹⁸F]fluoro-3′-deoxythymidine (¹⁸F-FLT) with regard to their feasibility for monitoring the tumor growth in orthotopic brain tumor mouse model.

Methods In orthotopic brain tumor mouse models bearing human glioblastoma, U87MG, clinical 3T T2-weighted MR images and small animal PET/CT images of FDG and FET at 60 min and FLT at 120 min post injection were obtained at day 22 after tumor injection and the images were compared.

Results Orthotopic brain tumor was visualized in T2-weighted MR images. As times goes by, tumor volume increased in both axial and coronal images. The tumor-to-normal brain (T/Br) ratio of FLT was significantly higher than those of FDG and FET (p < 0.05). There was no difference in FDG uptake between tumor and normal brain (p = 0.563). There was no difference (p = 0.517) in tumor uptake, but statistically significant difference in normal brain uptake and T/Br ratio among FDG, FET and FLT (p < 0.05).

Conclusions Due to physiologically high uptake of FDG in the brain, it was not feasible to distinguish the tumor from the brain. In contrast, FET and FLT was well accumulated in brain tumor, which was delineated from normal brain. These results suggest that FET and FLT small animal PET may provide the usefulness for monitoring brain tumor growth and therapeutic response by various therapeutic regimens in orthotopic brain tumor model

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FDG, FET and FLT uptake and ratio in orthotopic brain tumor model

*T/Br ratio; Tumor-to-normal brain ratio