In vivo labeling of red blood cells with 99mTc: a new approach to blood pool visualization.

A simple and rapid procedure for in vivo labeling of red blood cells (RBC) is presented. The labeling is done with two consecutive intravenous injections, first of "cold" stannous pyrophosphate (Sn-PYP) and then of 99mTc-pertechnetate. Experimentally, a lag time of 30 min between the two injections was found to result in a mean RBC labeling of greater than 95% during the first hour after pertechnetate injection. A total of 75 patients have been explored by scintillation camera imaging of brain, heart, great vessels, aortic bifurcation, testicles, and lower extremities using the technique outlined. High-quality images were obtained.