A, Cine CMR in a patient with aortic insufficiency. The three-chamber view during mid-diastole show a relatively dark signal intensity in the left ventricular outflow tract ( arrows ) that represents aortic regurgitation. The signal intensity changes are caused by dephasing and loss of signal from rapidly moving blood, but the appearance of regurgitant jets varies widely with different pulse sequences. On SSFP cine CMR, the jet size of aortic regurgitation is frequently less prominent than on color Doppler echocardiography or in-plane velocity encoded MR images. The stack of short axis images can be planimetered to measure left ventricular dimensions, volumes, and ejection fraction. In this case, the left ventricle is severely dilated (end-diastolic dimension 77 mm, end-systolic dimension 57 mm, end-diastolic volume 389 ml) with moderate eccentric hypertrophy (LV mass 283 g or 132 g/m ² , upper limits of normal less than 91 g/m ² ). There is mildly reduced global systolic function (LVEF 50%). B, Quantification of ascending aortic blood flow ( red circle ) and descending aorta ( blue circle ) using axial ECG-gated velocity-encoded phase contrast cine CMR. Anatomic and velocity-encoded phase contrast images through the ascending aorta are obtained simultaneously at the level of the main pulmonary artery bifurcation throughout the cardiac cycle. On phase contrast images, a white signal corresponds to cranial flow and a black signal corresponds to caudal flow. The gray signal intensity of the chest wall denotes stationary tissue, and the speckled appearance of the lungs and air outside the chest wall represents noise (regions with too weak a signal for velocity measurements). At end-diastole, there is little flow in either the ascending or descending aorta. At mid-systole, there is the expected cranial flow within the ascending aorta and caudal flow within the descending aorta. However, during mid-diastole, there is aortic flow reversal caused by severe aortic valve regurgitation with caudal flow within the ascending aorta and cranial flow within the descending aorta. By integrating the velocity of all pixels within a region of interest at each time frame, blood flow can be quantified as a function of time with no geometric assumptions. This is possible because CMR can quantify velocity through the imaging plane. The graph displays ascending aortic flow versus time from all 30 velocity-encoded phase contrast images acquired across the cardiac cycle. Positive values ( above the dotted line ) represent forward flow and negative values represent reverse aortic flow. In this patient with severe aortic insufficiency, the net forward aortic volume was 165 ml per cardiac cycle with a reverse volume of 84 ml per cardiac cycle, yielding a regurgitant volume of 81 ml or a regurgitant fraction of 51%.