SUMMARY Arterial compliance was measured in 70 healthy volunteers, 13 athletes, and 17 patients with coronary artery disease. Magnetic resonance images were acquired at end diastole and end systole through the ascending aorta, the aortic arch, and the descending thoracic aorta. Regional compliance was derived from the change in luminal area in a slice of known thickness and from the pulse pressure. Total arterial compliance was also measured from the left ventricular stroke volume and the pulse pressure. In the volunteers, mean (SD) regional compliance (Ml/mm Hg) was greatest in the ascending aorta (37 (18)), lower in the arch (31 (15)), and lowest in the descending aorta (18 (8)), and it decreased with age. Compliance in the athletes was significantly higher than in their age matched controls (41 (16) versus 22 (11) 1l/mm Hg). In the patients with coronary artery disease it was significantly lower (12 (4) v 18 (10)) than in age matched controls. Total arterial compliance also fell with age in those with coronary artery disease although there was more variation.The results suggest a possible role for compliance in the assessment of cardiovascular fitness and the detection of coronary artery disease.A popular saying is that a man is as old as his arteries. The commonest arterial disease is "hardening of the arteries" or atherosclerosis which leads, among other things, to a loss of elasticity. Arterial elasticity is measured as compliance, which is the change in volume per unit change in pressure, and compliance measurements may be valuable for both detection and monitoring of disease.Magnetic resonance imaging is a direct noninvasive way of studying regional aortic compliance and total arterial compliance. We used it to study changes in compliance with age and aortic compliance in athletes and in patients with coronary artery disease. Patients and methodsWe studied 70 Accepted for publication 7 March 1989 13 athletes (mean age 43, range 29-56), and 17 patients with coronary artery disease without previous infarction (mean age 53, range 30-76). Three of the athletes were of international standard (one Olympic gold medal) and the others were club athletes. The average distance run daily was nine miles.We used a Picker International Vista MR2055 machine operating at 0-5 T to acquire images at end diastole and end systole in three oblique planes perpendicular to the midpoints of the ascending aorta, the aortic arch, and the descending thoracic aorta (fig 1). A spin echo sequence (TE 40 ms) was used with two averages of 128 phase encoding steps, a pixel size of 1417 mm x 1-17 mm, and a slice thickness of 10 mm. The end diastolic images were acquired 100 ms before the average RR interval, and the end systolic images at the end ofthe T wave ofthe electrocardiogram Acquisition time was three to four minutes per image depending upon heart rate.The lumen of the aorta was outlined manually on the computer screen, and regional aortic compliance was calculated from the change in volume between diastole and systole. The p...

Four-dimensional magnetic resonance MR velocity mapping was developed to study normal flow patterns in the thoracic aorta using time-resolved cardiac gated threedirectional velocity data. Sixteen normal subjects were studied, one young group (average age 31 years) and one group with elderly people (average age 72 years). Blood flowed in a right-handed helix from the ascending aorta to the aortic arch. A straight flow pattern or a left-handed helix was seen in the descending aorta. Blood flow was never parabolic. Blood flowed forward in early systole, retrograde in mid-to-end systole, and forward again in diastole in all subjects as a basic pattern. Continuous retrograde flow over a long distance was not seen, but blood entered a retrograde flow column at various levels. In young people blood passed from the aortic valve to the mid-descending aorta in less than one heartbeat. In people in their sixties it took two heartbeats and in people older than 78 years, it took three heartbeats. The maximum systolic forward velocities were higher in young subjects than in elderly while the retrograde velocities were lower. J. Magn. Reson. Imaging 1999;10:861-869.1999 Wiley-Liss, Inc.Index terms: magnetic resonance velocity mapping; 4D aortic blood flow; blood flow in elderly; helical blood flow; blood flow patterns in one heartbeat THE FEASIBILITY of MR blood flow studies was suggested by Moran (1) and van Dijk (2). Clinical studies and verifications by Bryant et al (3), Nayler et al (4), and Firmin et al (5) followed soon thereafter. Klipstein et al (6) described blood flow patterns in the aorta with detailed velocity profiles, and Bogren et al (7) quantified ante-and retrograde flow. Two-directional velocity maps can be displayed as vector maps after computer animation of time-dependent flow fields in vessels or in the heart (8-14). Vector mapping has been used to describe the central flow fields in the normal aorta (15), in the pulmonary artery, in coarctation (14), and in aneurysms and grafts (16), and to analyze senescent blood flow changes and those caused by atherosclerosis (17). Vector mapping was performed in one slice only in the middle of the vessel to be examined, and each vector map represented the two-dimensional (2D) flow field in one slice of the imaged vessel during approximately 60-120 msec. Vector maps can be displayed in cine format. Even if 3D velocity mapping is performed and the third direction displayed separately, it is not a true 4D technique, since only one slice of the vasculature has been acquired and the data are not truly time resolved. Arrow maps reveal snap shots of the spatial organization of flow within the entire field. Streamline visualization was first used with non-gated 3D phase contrast angiography in the internal carotid artery and showed average flow trajectories and filling-time relationships (10). The method was subsequently improved by Buonocore (13), who later (18) described particle path visualization for time-resolved three-directional data sets in continuous slices covering t...

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The purpose of this study was to measure antegrade and retrograde flow in the aorta and the major arterial pathways in the body noninvasively with cine magnetic resonance (MR) velocity mapping, to determine the hemodynamic significance of retrograde flow in arteries. Two hundred forty cine velocity maps for blood flow measurements were obtained at 29 sites in the aorta and the major arteries in 31 healthy human subjects of varying age at rest. Synchronous or isolated antegrade and retrograde flow was found in the entire aorta and in arteries supplying muscles. No retrograde flow was found in arteries supplying internal organs, such as the internal carotid or splanchnic arteries. The retrograde flow in the aorta and the extremity arteries contributes substantially to supplying diastolic perfusion of internal organs such as the heart, brain, and kidneys. Antegrade flow tends to be helical in the thoracic aorta.