CATIONIC TC-99M COMPLEXES AS POTENTIAL MYOCARDIAL IMAGING AGENTS

Abstract

Nineteen cationic Tc-99m complexes, based upon 4 different ligand series, were synthesized under no-carrier-added conditions and qualitatively evaluated as myocardial imaging agents in a dog model. Of these complexes, the 4 halogen derivatives of the diars series [diars = o-phenylenebis(dimethylarsine)] successfully concentrate in the myocardium. These Tc-99m diars complexes are shown by TLC to be identical to the Tc-99 analogs that have been fully characterized as trans octahedral complexes of Tc(III) by classical chemical techniques. Tissue distribution studies in rats show a definite difference in the biodistributions of [99mTc(diars)2Cl2]+ and [99mTc(diars)2Br2]+, despite the similar size, shape, charge and lipophilicity of these 2 complexes. A tissue distribution study in resting beagle dogs shows that [99mTc(diars)2Br2]+ accumulates in the normal myocardium about half as well as Tl-201 (0.022 compared to 0.038% dose/g).