Preparation of ⁹⁹Tc^m-Gd-DTPA-Dimeglumine and Its Biologic Characteristics

The purpose of this study was to evaluate the feasibility of Gd-DTPA-Dimeglumine, as a contrast enhancer in magnetic resonance imaging(MRI). Gd-DTPA-Dimeglumine was labeled with ⁹⁹Tc^m, and its biologic characteristics were observed. The radiochemical purity and the stability of ⁹⁹Tc^m-Gd-DTPA-Dimeglumine were measured by TLC The labelling yield of ⁹⁹Tc^m-Gd-DTPA-Dimeglumine was＞95% and stable for at least 6 h at room temperature with the radiochemical purity more than 90%. The plasma protein binding rate of ⁹⁹Tc^m-Gd-DTPA-Dimeglumine was 2.25%±0.21%. The biodistribution in mice showed that ⁹⁹Tc^m-Gd-DTPA-Dimeglumine was excreted through kidney. The time of the highest uptake in all of the major organs was at 1 min after injection, and the decrease of deposition morn than 50% at 5 min after injection, and the brain and muscles have the lowest uptake rate less than 1%. The major organs have little uptake at 30-60 min after injection. Renal dynamic scintigraphy in rabbits were administrated via intravenous injection. The results indicated that ⁹⁹Tc^m-Gd-DTPA-Dimeglumine was quickly excreted by kidney, and the time to peak is about 5 min, the half time of clearance is about 7 min. It is a sample method with high labeling efficiency and radiochemical purity that Gd-DTPA-Dimeglumine labeled with ⁹⁹Tc^m, and its bio-distribution was not changed on the whole after labeled. The study indicated that DTPA as a bifunctional chelator may be linked with 99Tcm and Gd. So a type of new multimodality imaging agents with higher targeting characteristics, it could be applied both in SPECT and MRI scan.