FLOW PATTERN-ANALYSIS IN THE ABDOMINAL-AORTA WITH VELOCITY-ENCODED CINE MR-IMAGING

The sites of deposition of atherosclerotic plaque on the aortic wall a re considered to be influenced by secondary and retrograde flow patter ns that cause regions of altered shear stress. To detect secondary flo w patterns and areas of retrograde flow in the abdominal aorta, veloci ty-encoded cine (VEC) magnetic resonance (MR) imaging was performed at five different levels of the abdominal aorta in nine healthy voluntee rs. Net retrograde flow (expressed as a percentage of antegrade flow) increased from proximal to distal levels and was maximal (13.8% +/- 11 .8) just distal to the origin of the renal arteries. An increase in th e duration of retrograde flow over the cardiac cycle was observed from proximal to distal levels. Whereas retrograde flow was present at end systole and early diastole in each volunteer at every level, the dura tion and amount of retrograde flow during diastole showed high interin dividual variation. Such differences suggest the possibility of variab le vascular geometric risk factors in the population for the developme nt of atherosclerotic plaque. The location of retrograde flow in the a bdominal aorta demonstrated in vivo with VEC MR imaging was close to t hat obtained with in vitro flow visualization studies in models of the abdominal aorta.