Mural thrombi in abdominal aortic aneurysms: MR imaging characterization-useful before endovascular treatment?

PURPOSE: To evaluate magnetic resonance (MR) imaging accuracy in the characterization of mural thrombi in abdominal aortic aneurysms (AAAs). MATERIALS AND METHODS: Forty-five patients (37 men, eight women; mean age, 68 years) with an AAA with mural thrombus thicker than 1 cm at sonography underwent T1- and T2-weighted spin-echo MR imaging. The thrombi were prospectively classified as one of three signal intensity (SI) categories: category 1 corresponds to low SI on both T1-and T2-weighted images; category 2, high SI on T1- and T2-weighted images; and category 3, inhomogeneous SI with hyperintense areas on both T1- and T2-weighted images. During surgery, thrombi were classified as organized, unorganized, and partially organized. MR imaging and surgical findings were compared. RESULTS: SI category 1 corresponded to organized thrombi in 24 of 24 patients. Category 2 corresponded to unorganized thrombi in 11 of 11 patients. In category 3, focal hyperintense areas corresponded (both for presence and location) to unorganized portions of partially organized thrombi in 10 of 10 patients. CONCLUSION: MR imaging is accurate in AAA thrombus characterization.