Imaging of deep venous thrombosis using radioactive-labeled tirofiban.

The development of radiolabeled small peptide or peptidomimetic ligands can bind platelets and their specific expressed receptor have been suggested as a new approach to detect the clot location and, more essentially, to determine the age and morphology of the evolving thrombus. This new approach is focused on the use of a series of radiolabeled platelet GPIIb/IIIa receptor antagonists. Tirofiban N-(butylsulfonyl)- 4-O-(4-(4-piperidyl)-L-tyrosine is a non-peptide tyrosine derivate. The aim of the study was to introduce radioactive-labeled tirofiban as a specific imaging agent for acute DVT. The labeling was performed with technetium-99 in the presence of a stannous reducing agent. The labeled preparation showed fast blood clearance in a normal rat model (without induced thrombosis). More than 80% of the injected dose was eliminated from the circulation in the first hour after injection. Biodistribution and visualization of the labeled molecule was carried out using an experimental model of thrombosis in a male Wistar rat. Planar images were obtained 30 and 60 min after application of 2×10(6) imp/min 99m-technetium-tirofiban in the rat's tail vein. Sensitivity and specificity were determined using the ratio of 'left leg positive for DVT' to 'right leg negative for DVT'. The obtained ratio was 1.54 after 30 min and 5.04 after 60 min. These values were considered positive in the detection of acute DVT. The high DVT uptake shows that radiolabeled tirofiban in the introduced rat model can be a promising agent for imaging the deep venous thrombosis (Fig. 7, Ref. 25).