Stoichiometric Tc-99m RBC labeling using stable kit solutions of stannous chloride and EDTA: concise communication.

An in vitro Tc-99m labeling method is described, which utilizes stable stock solutions of stannous chloride and disodium edetate (EDTA). The kit procedure requires as little as 1 ml of patient blood, can be performed in only 15 min, and gives labeling yields in excess of 98%. By using EDTA, the binding capacity of RBCs for technetium is sufficient to produce Tc-99m RBC doses with specific concentration greater than 50 mCi/ml for first-pass cardiac studies. Scintigrams reveal a slight amount of bladder activity and splenic uptake, but at no time has the thyroid, stomach, or normal bowel been visualized. The predominant 20-hr blood-clearance half-time results in excellent image quality for over 24 hr--an essential property for following intermittent GI bleeding or for performing repeat cardiac function studies over a several-hour time interval.