fig4

Figure 4. Aortic tortuosity index (TI) value is obtained by dividing the interested aortic length measured at center line by the geometric length (A/B= TI) (I). Radius of curvature is an approximative measure of aortic arch curvature. The higher the “r” value, the less curved the arch can be considered (II). Aortic arch angle is calculated at the highest point of the aortic arch between a line toward a mid-arterial point in the ascending aorta and one in the descending at the level of pulmonary artery bifurcation (III).