Comparison of ‘classic’ 99mTc–DTPA, 99mTc(CO)3–DTPA and 99mTc(CO)2(NO)–DTPA

Diethylenetriamine pentaacetic acid (DTPA) was labeled with 99mTc in three different ways, resulting in ‘classic’ 99mTc–DTPA, 99mTc(CO)3–DTPA and 99mTc(CO)2(NO)–DTPA. The biodistribution of the formed DTPA-complexes was studied in mice with a special emphasis on the behavior of the novel tricarbonyl and dicarbonyl-nitrosyl complexes, which was clearly differing from that of ‘classic’ 99mTc–DTPA. The conversion of a Tc-tricarbonyl complex to a Tc-dicarbonyl-nitrosyl complex using NO+ reagents offers a synthetic tool for preparing a novel class of 99mTc labeled compounds.