Newer methods of labeling diagnostic agents with Tc-99m

The past several years have seen marked advances in technetium/rhenium chemistry applicable to the preparation of new 99mTc-labeled radiopharmaceuticals. This article focuses on recent developments in technetium chemistry, including the preparation of "3 + 1" complexes, the preparation and use of (99mTc[CO]3)+ complexes for labeling biomolecules, the preparation of rhenium steroid inclusion complexes, improvements in both hydrazinonicotinamide labeling chemistry and in the preformed 99mTc complex method of labeling biomolecules, and new solid-phase separation techniques that may allow the isolation of high specific-activity radiopharmaceuticals in a clinical setting.