The kinetics of copper-62-PTSM in the normal human heart

Copper-62-labeled pyruvaldehyde bis(N-4-methylthiosemicarbazone) copper(II) (PTSM) is a generator-produced myocardial perfusion tracer. Animal studies have shown high myocardial tissue extraction and prolonged retention. The aim of this study was to define myocardial kinetics of 62Cu-PTSM and to determine its suitability for evaluating myocardial perfusion at rest and during pharmacological vasodilation in human subjects. In six healthy volunteers, 62Cu-PTSM was administered at baseline and during a 6-min adenosine infusion (140 micrograms/kg/min). Dynamic PET imaging with high temporal resolution was performed over 20 min. Good image quality was observed at rest and following adenosine. Myocardial kinetics demonstrated prolonged tissue retention with a clearance half-life of 105 +/- 49 min at rest and 101 +/- 65 min following adenosine (p = ns). Copper-62-PTSM tissue retention was quantified and showed only a 1.97-fold increase from rest to adenosine studies. This suggests attenuation of tracer retention at high flow rates. Copper-62-PTSM represents a promising new radiopharmaceutical for the evaluation of myocardial perfusion in the human heart.