The preparation and biodistribution of a technetium-99m triaminodithiol complex designed to reflect regional cerebral blood flow

Recently, interest in the development of radiotracers for brain imaging has increased. Technetium complexes of diaminodithiol (DADT) ligands have been shown to be stable, neutral, lipid soluble, and shown to cross the blood:brain barrier. A new ligand, N-Piperidinylethyl-DADT has been synthesized which forms two complexes with Tc-99m when stannous chloride is used as a reducing agent for Tc-99m pertechnetate. Biodistribution studies of both complexes in mice showed one to have a 2.2% of the injected dose of the tracer in the brain at 5 minutes post intravenous injection with 0.53% of the dose remaining in the brain at 30 minutes post injection. Brain-to-blood ratios at these times were 5.3 and 3.0 respectively. Imaging studies were conducted in a monkey and a baboon in which rapid uptake of the tracer in the brain was observed and clear brain images were obtained. Time activity curves showed peak uptake in the brain at approximately 5 to 7 minutes post intravenous injection followed by a plateau of about 11 minutes. The half-lives for clearance of the tracer from the brains of the monkey and baboon were found to be 63 and 58 minutes respectively. This preliminary evaluation suggests that this tracer shows promise formore » brain imaging in humans.« less