Effects of chelates and incubation media on platelet labeling with indium-111.

We studied the effects of various [111In]chelates and incubation media on labeling efficiency (LE) and in vivo survival of platelets. High LE of human and rabbit platelets in plasma were obtained with [111In]tropolone and [111In]mercaptopyridine-N-oxide. Indium-111 oxine in plasma resulted in a moderate LE and required a longer incubation time, while [111In]oxine sulfate had low LE and inconsistent labeling. High LE for all forms of [111In]chelates were achieved in labeling media free of plasma. However, in vivo platelet survival in rabbits was markedly reduced when platelets were labeled in the absence of plasma.