New technetium 99m-labeled brain perfusion imaging agents.

In developing new brain perfusion imaging agents, three types of neutral and lipid-soluble technetium 99m complexes have been reported: 99mTc-ethylene cysteinate dimer, 99mTc-hexamethyl propylene amine oxime, and 99mTc-boric acid adduct of technetium oxime. Structure-activity relationships of these complexes on brain uptake and retention have been investigated. The new 99mTc-brain perfusion imaging agents are useful in detecting various cerebral vascular abnormalities. The exact trapping mechanisms and their relationship with potential clinical applications still remain to be elucidated. However, initial clinical studies with 99mTc agents do show parallel clinical efficacy as those reported for the iodine 123-labeled brain perfusion agents, isopropyliodoamphetamine and N,N,N'-trimethyl-N'-[2-hydroxy-3-methyl-5-iodobenzyl]-1,3-propanediamine .