Small Peptide Radiopharmaceuticals in the Imaging of Acute Thrombus

Until recently, imaging acute thrombus, especially the very prevalent condition of acute deep vein thrombosis relied on conventional imaging techniques utilizing either ultrasonography or contrast venography. The former procedure is limited by accuracy and the latter by technical considerations. Newer modalities such as magnetic resonance and computed tomographic scanning are yet to be validated in a prospective manner. Recent advances in the understanding of the pathogenesis of acute clot at the molecular level have suggested new avenues for detection of the acute thrombotic process based on the biomolecular behavior of components of the clotting process including the formed element of the blood, the platelet. Expression of a receptor on platelets unique to acute thrombosis and synthesis of small peptide ligands with high specificity for that receptor have suggested a new venue for evaluation of acute venous thrombotic disorders. The challenges of ligand synthesis for the integrin glycoprotein receptors on platelets are discussed along with the difficulties of incorporation of a convenient nuclide for imaging purpose, 99mTc. The absence of specificity for acute clot in established “gold standard” tests including contrast venography suggests that small peptide directed ligand-receptor imaging may provide superior information based on the biomolecular behavior of the clotting process.