Cross-sectional deformation of the aorta as measured with magnetic resonance imaging

Vessel geometry is commonly accepted as one of the primary factors influencing blood flow patterns. The vessels near the heart present a particular challenge because myocardial contraction creates dynamic changes in vessel geometry due to the movement created by the contraction of the myocardial muscle. The importance of vessel movement and deformation on blood flow patterns in the coronary arteries has been previously demonstrated. For larger vessels such as the aorta, the effects are less well understood, partially because no estimates of the dynamic variations in vessel cross section shape geometry have been reported. This study was undertaken to provide an estimate of the amount of dynamic variation in cross-sectional shape present in the aorta. Two young healthy male subjects were used, with measurements taken in the ascending aorta, aortic arch, and descending thoracic aorta using Magnetic Resonance Imaging (MRI). The magnitude of elliptical deformation was measured throughout the cardiac cycle by taking a discrete Fourier transform of the radius versus angle plot. Deformations of more than 7 percent of the mean vessel radius were noted. This level of deformation may be enough to influence flow patterns in the aorta significantly, and thus should be included in future flow studies.