Molecular MRI of cerebral venous sinus thrombosis using a new fibrin-specific MR contrast agent

Background and Purpose - Imaging of cerebral vein thrombosis is still challenging. Currently, diagnosis is based on CT venography and MRI including MRA and conventional digital subtraction angiography. However, especially in chronic cases, each method has shown its limitations. Newer strategies for MRI are found on molecular imaging using targeted contrast agents. The aim of this study was to prove the feasibility of a novel fibrin-targeted MR contrast agent (EP-2104R; EPIX Pharmaceuticals) for selective imaging of sinus venous thrombosis in an animal model. Methods - Thrombosis of the superior sagittal sinus with human blood was induced in 6 pigs using a combined microsurgical and interventional approach. MRI was then performed before and up to 120 minutes after injection of 4 mu mol/kg body weight EP-2104R. Molecular imaging was performed with a 3- dimensional high-resolution T1-weighted gradient echo sequence. Time courses of signal-to-noise ratio and contrast-to-noise ratio were analyzed. Thrombi were then surgically removed and the Gadolinium concentration was assessed. Results - In all cases the thrombosis could be successfully induced; the complete MR protocol could be performed in 5 animals. In these cases the thrombi showed selective enhancement after injection of the molecular contrast agent. However, a continuous contrast-to-noise ratio increase was seen up to 120 minutes after contrast administration, achieving a contrast-to-noise ratio of 14.2 +/- 0.7 between clot and the blood pool. Conclusion - The novel fibrin-targeted molecular MR contrast EP-2104R allows selective and high- contrast imaging of cerebral sinus vein thrombosis in an animal model.