Comparison of magnetic resonance imaging methods for examinations of abdominal aortic aneurysms

Different magnetic resonance imaging techniques were compared with respect to available anatomic information regarding abdominal aortic aneurysms (AAA) and regions involved in thrombosis.

Twenty patients with AAA were examined by turbo spin-echo (TSE) imaging of coronal and transverse slices, resulting in black blood images. Bright blood imaging was performed using a spoiled gradient-echo sequence with gradient moment nulling. Sets of 25 to 50 thin slices were recorded sequentially in a single slice mode using coronal and transverse orientation. Both sets of bright blood images were reconstructed by maximum intensity projection.

In all patients, the size and shape of the AAA could better be assessed by the TSE images than by the gradient-echo images. In contrast, reliable differentiation of thrombotic areas and of the perfused lumen was possible in only 56% of the slices recorded by TSE imaging but in 94% of the gradient-echo images. The two-dimensional inflow technique provided clearly higher sensitivity even to slow blood flow than TSE imaging. Maximum intensity projection reconstructions from sets of coronal two-dimensional inflow images often did not depict the lower part of the AAA because of saturation effects, whereas sets of transverse slices provided complete angiograms of the aortoiliac vascular tree.

At this time, no single magnetic resonance method can provide all essential information. A comprehensive examination should include TSE imaging for topographic assessment and transverse two-dimensional inflow imaging for analysis of thrombotic areas.