TC-99(M)-DIMERCAPTOPROPIONYL-HSA PREPARED FROM A LABELING KIT - PRELIMINARY INVESTIGATIONS AS A BLOOD-POOL AGENT

The blood retention of Tc-99(m)-dimercaptopropionyl human serum albumi n (Tc-99(m)-DMP-HSA), prepared from a kit, was compared with that of f ive other Tc-99(m)-labelled blood pool tracers in two healthy voluntee rs. Tc-99(m)-DMP-HSA showed an almost identical behaviour to in vitro labelled red blood cells (RBCs), which are generally considered the re ference standard for blood pool agents. The mean apparent blood mass o f Tc-99(m)-DMP-HSA was 2.1% higher 10 min post-injection (p.i.) than t hat of in vitro Tc-99(m)-RBCs, 2.0% higher 30 min p.i., 4.7% higher 60 min p.i. and 2.3% higher 120 min p.i. In vivo labelling of RBCs yield ed a labelling efficiency of 75-98%, depending on the stannous agent u sed. About 20 min after pertechnetate administration, the intravascula r activity as a percentage of injected dose stabilized at levels close to that of in vitro labelled RBCs. One commercially available Tc-99(m )-HSA kit was found to be unsuitable as a blood pool tracer. As Tc-99( m)-DMP-HSA offers the same practical advantages as Tc-99(m)-HSA, but b etter biological characteristics, it shows promise as a new tracer for radionuclide ventriculography and further large-scale investigations are warranted.