From Molecular Imaging to Pathogenesis and Vice Versa…
- magnetic resonance imaging
- positron-emission tomography
- tomography, emission-computed, single-photon
Thrombi are fibrin-laced platelet plugs, which maintain the vascular integrity after endothelial damage. Loss of endothelial integrity exposes the platelets in the blood to prothrombotic substrates in the vascular wall and causes platelet activation. The activated platelets express surface molecules including glycoprotein IIb/IIIa and P-selectin, which allow aggregation of platelets into a plug, and secrete substances to activate and attract other platelets. Endothelial damage also activates coagulation cascades, leading to the formation of thrombin. Thrombin converts fibrinogen into fibrin strands, which are cross-linked by factor XIII (FXIIIa), resulting in the formation of the fibrin network bracing the platelet plug. In addition, thrombin causes further platelet activation. Inappropriate or excessive formation of thrombus is the cause of pulmonary emboli, deep venous thrombosis, myocardial infarction, and cerebral stroke. Besides endothelial damage, stasis of blood and procoagulative state of the blood can cause or contribute to thrombus formation in the pathological settings.
Article see p 697
The Present Study
In this issue of Circulation: Cardiovascular Imaging, Ay et al1 describe in vivo detection of thrombi by positron emission tomographic imaging using 64Cu-fibrin-binding probe 7 (FBP7), a small fibrin-targeted cyclic peptide. The authors report high target-to-background ratio of the tracer uptake in rats with carotid crush injury-induced mural thrombosis and in rats after intracarotid thrombus placement. Moreover, the tracer allowed in vivo monitoring of thrombus dissolution over time after recombinant tissue-type plasminogen activator treatment. The authors claim that a clinically applicable molecular imaging technique to visualize thrombi components may be a valuable tool. First, whole body imaging with such a probe could be applied for more sensitive and precise thrombus detection. This would be particularly useful in the situations where thrombus diagnosis is difficult, such as in cases of chest pain or stroke of unknown origin, suspected endocarditis, or intracardiac thrombus. Second, molecular imaging …