Fig. 2

Curvature and tortuosity. At left, the thoracic aorta tortuosity index is determined by taking the ratio of the center lumen line distance from the ostium of left common carotid artery to the ostium of the superior mesenteric artery, and the straight line distance between the same two points. At top right, the intraaortic distance is calculated as half the minimum distance between the inner curvature of the ascending aorta to the inner curvature of the descending aorta at the most superior level at which the bifurcation of the pulmonary artery can be observed. At bottom right, arch type is determined by the vertical distance from the (middle of the) origin of the innominate artery to the top of the arch. Type I: < 1 diameter of the LCCA. Type II: between 1 and 2 LCCA diameters. Type III: > 2 LCCA diameters