Magnetic resonance velocity vector mapping in aortic aneurysms

Abstract

We used magnetic resonance imaging with cine velocity vector mapping to study blood flow patterns in the thoracic aorta of patients with aortic aneurysms. Spin-echo images of the thoracic aorta were acquired in orthogonal and oblique planes. Cine phase-shift velocity maps were then acquired in selected aortic planes, with velocity encoded in two orthogonal directions. The two-directional velocity data were processed to generate flow vector maps depicting flow distribution in the chosen plane. Diameter ratios between the aortic valves and aneurysmal ascending aortas were reduced, causing blood to enter as a relatively narrow stream with lateral vortical, recirculating flow. In atherosclerotic aneurysms, there was abnormal angulation between the left ventricular outflow tract and ascending aorta, causing the stream to attach to the anterior aortic wall, with recirculating flow posteriorly. In Marfan patients, the primary stream was central with vortices on either side. In patients with coarctation, the main stream attached to the posterior wall of the descending aorta, with recirculation anteriorly. Magnetic resonance imaging with cine velocity mapping allows comprehensive assessment of aortic anatomy and blood flow patterns. Sequential studies at early stages may provide new information about the natural history of aortic aneurysms.