Image analysis
Image analysis was conducted according to a standardized protocol. CTA
analysis was conducted by manually demarcating an aortic centerline
extending from the level of the aortic valve anulus through the origin
of the left subclavian artery. Curved planar reformatted images were
generated using the aortic centerline as the reference point (Figure 1).
The sinotubular junction (STJ) and the origin of the innominate artery
(IA) were then identified and labeled (Figure 2). The STJ was defined as
the earliest point that the ascending aorta becomes tube-like. The
origin of the IA was defined as the most proximal point at which the
wall of the IA touches the ascending aorta (rather than at the middle of
the IA lumen). The path length, distance, and tortuosity between the STJ
and IA were recorded. The pulmonary artery bifurcation was identified in
transverse plane and measured at the widest point of both the left and
right branches of the PA (Figure 2). Cross-sectional area, average
diameter, maximum diameter, and minimum diameter were measured at the
levels of the STJ, IA, and PA bifurcation.