A comparative evaluation of techniques for rapid and efficient in vivo labeling of red cells with [99mTc]...

Red blood cells (RBCs) labeled in vivo with 99mTcO4- have recently been recommended for blood-pool imaging, but the optimum conditions for in vivo labeling of RBCs have not been clearly defined. We therefore evaluated several stannous-ion preparations and stannous-ion concentrations to determine which provided the best labeling. The effect of the time interval between the Sn(II) and 99mTcO4- injections and the effect of carrier technetium on labeling efficiency were also studied. Maximal in vivo labeling efficiency was obtained using an intravenous dose of 10 microgram Sn(II)/kg followed 5-30 min later by an injection of 99mTcO4-. Neither the chelated form of stannous ion used in these studies nor the amount of carrier present had a significant effect on labeling efficiency. The biologic half-time of Tc-99m RBCs labeled in vivo was similar to that of Tc-99m RBCs labeled in vitro. In vivo labeling is a rapid and efficient method for the preparation of Tc-99m RBCs.