99mTc-HM-PAO for leukocyte labeling--experimental comparison with 111In oxine in dogs.

99mTc-hexamethylpropylene amine oxime d,l diastereoisomer (HM-PAO), developed as a diffusible brain imaging agent, labels leukocyte suspensions in saline with an efficiency of 80% using 1-200 micrograms quantities. In dogs, the recovery and survival of reinjected cells in the bloodstream resemble those of 111In-oxine labeled cells at least for several hours. Images in control animals at 18 h show the spleen, liver, marrow, and bladder, minimal pulmonary activity and some gastrointestinal activity. Induced E. coli abscesses and joint inflammatory lesions in dogs are shown on 18 h images. This complex appears promising as an agent for abscess detection in humans. However, strict quality control of this agent is necessary, and it must be used immediately after the 99mTc complex is formed for labeling cells.