Purpose:

To determine the feasibility of detecting thrombi using a fibrin-specific gadolinium-based magnetic resonance imaging contrast agent, EP-2104R.

Methods:

Subjects with confirmed thrombus in the venous system (n= 14), or in the heart, or arterial system (n= 38) were enrolled. Patients were imaged before and at various times following a 4 μmol/kg intravenous bolus injection of EP-2104R:< 1 hour (N= 16), 2 to 6 hours (N= 36), and/or 20 to 36 hours (N= 33). Images were assessed by investigators at each site and by a single reader not affiliated with the sites to determine whether thrombi were visible, not visible, or further enhanced with EP-2104R. A subset of data was analyzed quantitatively by measuring a signal intensity relative to background tissue.

Results:

Overall, 29 thrombi were visible before contrast administration, 3 of 14 in the venous system, and 26 of 38 in the arteries and heart. Thrombi generally enhanced in signal after EP-2104R injection, and an additional 7 were visualized. After contrast, 4 of 14 thrombi were visible in the venous system, and 32 of 38 in the arteries and heart. Thrombi were more conspicuous when imaged at 2 to 6 hours post EP-2104R compared with within 1 hour, because of lower blood background. Quantitatively, the post: pre signal intensity ratio was 1.90 at 2 to 6 hours post injection (standard deviation= 1.08, N= 20, P< 0.001); and 2.04 (standard deviation= 1.29, N= 19, P< 0.0025) for the 20 to 36 hours time point. There were no serious adverse events considered related to study drug.

Conclusion:

EP-2104R enhanced magnetic resonance imaging detects thrombi not readily visible in precontrast screening and gives additional enhancement of thrombi that are visible in precontrast imaging.