Tc-99m HMPAO as a Potential Platelet Labelling Compound: First in Vivo and in Vitro Results

First results of platelet labelling with Tc-99m hexamethylproplene-amineoxime (HMPAO) in-vitro (n=7) and in-vivo (n=3) are described. After platelet isolation the best incubation time is 20 min (37°C). The in-vitro Tc-99m elution out of platelets amounts to about 7%/60 min. After reinjection of the labelled cells, the organ distribution of Tc—99m is comparable to activity distribution patterns after In-1ll-oxin labelling with a maximum in the spleen, minor activity in the liver and total visualisation of the blood pool. Already after reinjection of the cells a kidney and bladder activity can be seen as a consequence of tracer excretion. The localisation of bowel activity after 2h p.i. also is a consequence of a Tc-99m complex elution through the intestine. A positive demonstration of Tc-99m HMPAO labelled platelets uptake in a fresh thrombus can be demonstrated.