A potential copper radiopharmaceutical for imaging the heart and brain: copper-labeled pyruvaldehyde bis(N4-methylthiosemicarbazone).

An investigation of the biodistribution of lipophilic copper-64 (half-life = 12.7 h) compounds has been initiated in order to screen potential tracers that could be used to measure regional cerebral and/or myocardial blood flow when labeled with generator-produced 62Cu. The 64Cu complex of pyruvaldehyde bis(N4-methylthiosemicarbazone), [64Cu]Cu-PTSM, was prepared and found to be lipophlic (octanol/saline partition coefficient, log p = 1.97 +/- 0.03). Biodistribution studies following i.v. injection of [64Cu]Cu-PTSM into rats show tracer uptake by the brain and heart. At 1, 5, and 15 min post-injection 3.3, 3.0 and 2.7% of the injected dose was found in the brain. Corresponding brain to blood ratios (per gram) were 3.2, 3.6 and 4.0 respectively. Heart to blood ratios of 7.6, 7.6 and 7.3 were observed at these same time points.