Imaging with 99mTc ECDG targeted at the multifunctional glucose transport system:: Feasibility study with rodents

PURPOSE: To evaluate the feasibility of technetium 99m (Tc-99m) ethyleneclicysteine-deoxyglucose (ECDG) imaging in tumor-bearing rodents. MATERIALS AND METHODS: ECDG was synthesized by means of reacting ethyl-enedicysteine with glucosamine, with carbodiimide as the coupling agent. Hexokinase assays were performed at an ultraviolet wavelength of 340 nm. To determine whether blood glucose level could be altered, ECDG or glucosamine was injected into six rats. In a separate study, ECDG followed by insulin was administered to three rats. To determine biodistribution, lung tumor cells were intramuscularly injected into the hind legs of 18 nude mice. The animals were then injected with Tc-99m ECDG or fluorine 18 (F-18) fluorodeoxyglucose (FDG) (0.037-0.074 MBq per mouse). Radioactivity was measured in tissue excised from the animals. Scintigraphy was performed in three groups: in group 1 to demonstrate that different-sized tumors could be imaged after Tc-99m ECDG administration, in group 2 to ascertain whether tumor uptake of Tc-99m ECDG was perfusion related, and in group 3 to demonstrate that tumor uptake of Tc-99m ECDG occurred by means of a glucose-mediated process. RESULTS: ECDG was positive for phosphorylation at hexokinase assay. Blood glucose level increased with ECDG injection and decreased with insulin administration. Tumor-to-brain tissue and tumor-to-muscle tissue ratios of 99mTc ECDG uptake were higher than those of F-18 FDG uptake. Scintigraphic results demonstrated the feasibility of Tc-99m ECDG imaging. CONCLUSION: There are similarities between Tc-99m ECDG uptake and F-18 FDG uptake in tumors, and study findings supported the potential use of Tc-99m ECDG as a functional imaging agent. (C) RSNA, 2003.