MR imaging of thrombi using EP-2104R, a fibrin-specific contrast agent: initial results in patients

This study was an initial phase II trial in humans of molecular magnetic resonance (MR) imaging for improved visualization of thrombi in vessel territories potentially responsible for stroke using a new fibrin-specific contrast agent (EP-2104R). Eleven patients with thrombus in the left ventricle (n=2), left or right atrium (n=4), thoracic aorta (n=4) or carotid artery (n=1) as verified by an index examination (ultrasound, computed tomograpy, or conventional MR) were enrolled. All MR imaging was performed on 1.5 T whole-body MR- system using an inversion-recovery black-blood gradient-echo sequence. The same sequence was performed before and 2-6 h after low-dose intravenous administration of 4 mu mol/kg EP-2104R. Two investigators assessed image quality and signal amplification. Furthermore, contrast-to-noise ratios (CNR) between the clot and the blood pool/surrounding soft tissue before and after administration of the contrast agent were compared using Student's t-test. MR imaging and data analysis were successfully completed in 10 patients. No major adverse effects occurred. On enhanced images, thrombi demonstrated high signal amplification, typically at the clot surface, with a significantly increased contrast in comparison to the surrounding blood pool and soft tissue (CNR for clot vs. blood pool, unenhanced and enhanced: 6 +/- 8 and 29 +/- 14; CNR for clot vs. soft tissue, unenhanced and enhanced: 0 +/- 4 and 21 +/- 13; P<0.01 for both comparisons). EP-2104R allows for molecular MR imaging of thrombi potentially responsible for stroke. High contrast between thrombus and surrounding blood and soft tissues can be achieved with enhanced imaging.