A gallium-68 radiopharmaceutical that is retained in myocardium: 68Ga[(4,6-MeO2sal)2BAPEN]+

Abstract

The cationic gallium(III) complex formed with the bis(4,6-dimethoxy)salicylaldimine of N,N'-bis(3-aminopropyl)ethylenediamine has been investigated as a potential 68Ga radiopharmaceutical for imaging the heart with PET. The 67Ga complex of this ligand was prepared by ligand exchange from 67Ga-acetylacetonate and its biodistribution determined in ether anesthetized rats following intravenous injection. At 1 min postinjection, 1% of the injected dose was found in the heart with heart-to-blood and heart-to-lung ratios of 2.3:1 and 1.9:1, respectively. No clearance of 67Ga radioactivity from the heart was observed over the 1-min to 2-hr time frame studied. The 68Ga complex of this ligand was also prepared and the tracer further evaluated in a PET imaging study with a normal dog. Beyond 20 min postinjection, the heart was clearly delineated in the 68Ga PET images with good heart-to-blood and heart-to-lung contrast. No clearance of myocardial 68Ga radioactivity was observed over the 90-min imaging period, which is consistent with the results obtained in the rat. Gallium-68 complexes of this type may be useful as radiopharmaceuticals for imaging the heart with PET.