Magnetic resonance imaging of abdominal aortic aneurysms.

Magnetic resonance imaging (MRI) was performed in 20 patients with radiologically or surgically proven abdominal aortic aneurysms using a Siemens Magnetom scanner with a 0.35-T superconductive magnet. On MRI, rapidly flowing blood emits little or no signal and appears black; stagnant blood, turbulent flow, and atheromatous plaques produce signals of various intensities and are imaged as light to medium gray. Of nine patients who underwent surgical repair, MRI correctly demonstrated the origin of the aortic aneurysm in nine and accurately determined the status of the iliac arteries in eight. In two patients in whom intravenous contrast administration was contraindicated, MRI provided the correct diagnosis of a mycotic pseudoaneurysm in one and clearly distinguished the iliac arteries from the surrounding fibrosis in the other. Of 11 patients who did not have surgical repair, MRI findings correlated well with other radiologic studies. MRI was found to be more reliable than sonography in determining the relation between the aneurysm and the renal arteries as well as the status of the iliac arteries. Despite these advantages, the authors still advocate sonography as the screening procedure of choice in patients with suspected abdominal aortic aneurysms because of its lower cost and east of performance. MRI should be reserved for patients who have had unsuccessful or equivocal sonographic examinations.