Preparation and biodistribution of the (TcN)-Tc-99m-CPDTC complex as a newpotential brain perfusion imaging agent

The complex (TcN)-Tc-99m-CPDTC (CPDTC: N-cyclopropyl dithiocarbamate trihyd rate) is synthesized through ligand-exchange reaction. The two-step procedu re involves the initial reaction of (TcO4-)-Tc-99m with succinic dihydrazid e(SDH) as a donor of nitrido ligand(N3-) in the presence of stannous chlori de dihydrate as reducing agent and propylenediamine tetraacetic acid (PDTA) as complex agent, followed by the addition of sodium N-cyclopropyl dithioc arbamate trihydrate. The radiochemical purity( RCP) of the product is over 90% as measured by thin layer chromatography (TLC). It is stable over 6 h a t room temperature. Its partition coefficient indicates it is a good lipoph ilic complex. The biodistribution results in mice indicate that (TcN)-Tc-99 m-CPDTC is significantly retained into the brain. The brain uptake(% ID/g) is 4.64, 3.54 and 2.59 and the brain/blood ratio is 1.08, 1.27 and 1.28 at 5, 30 and 60 min post-injection respectively. These results suggest potenti al usefulness of the complex as a brain perfusion imaging agent.