Technetium-99m complexes of EDTA analogs: Studies of the radiochemistry and biodistribution

The preparation of technetium-99m aminopolycarboxylate complexes was carried out under anerobic conditions using stannous ions as the reducing agent. Electrophoresis and thin layer chromatography were used for analysis, showing that DTPA, EDTA and 1-methyl-EDTA preparations contained most of the ⁹⁹m-Tc radioactivity in the chelate form. Kinetic studies showed that binding to 1-phenyl-EDTA was slow. All compounds migrated towards the anode on electrophoresis, enabling separation from free pertechnetate and reduced ^99mTc. Quantitative distribution studies in mice and computerized renograms in rabbits showed that renal clearance was the main excretory route, but all compounds were cleared more slowly than ¹³¹-hippuran. The presence of the lipophilic phenyl group in the EDTA molecule produced excretion partially by the biliary route. These complexes belong to a series of bifunctional chelates which has the potential to produce new ^99mTc-radiopharmaceuticals having the in vivo stability of ⁹⁹Tc-EDTA.