AIMS OF THE COLOGNE-SYMPOSIUM ON RADIOLABELLED PLATELETS In 1976, M. Thakur et al (1) were the first to publish a paper concerning the in vivo thrombus detection with 111- In-labelled platelets. Previous attempts at scintigraphic thrombus localisation had been disappointing because of the unspecific binding of a number of the isotopes used, as well as the poor labelling efficiency or an insufficient low gamma-emitting property. Because of its physical characteristics (2.8 days half-life, 94% gamma emission) 111 Indium turned out to be the best isotope for platelet kinetic studies as well as...