Evaluation of radiolabeled fragment E1 as an agent for localization of aged and fresh thrombi in vivo

Radioiodinated Fragment E1 (a dimeric molecule derived from the plasmin digestion of cross-linked fibrin), which exhibits high specificity for fibrin polymers in vitro, binds specifically to both fresh and aged venous thrombi in vivo in a pig model. Because Fragment E1 clears fairly rapidly from the blood, it may provide a detectable thrombus-to-blood ratio in less than 24 hours post injection. Fragment E1, labeled to a high specific activity with a suitable gamma-emitting radionuclide, should be capable of localizing thrombi and other sites of fibrin deposition in any area of the body. Clinical studies are now in progress