An increasing number of intermediate risk asymptomatic subjects benefit from measures of atherosclerosis burden like coronary artery calcification studies with non-contrast heart computed tomography (CT). However, additional information can be derived from these studies, looking beyond the coronary arteries and without exposing the patients to further radiation. We report a semi-automatic method that objectively assesses ascending, arch and descending aorta dimension and shape from non-contrast CT datasets to investigate the effect of aging on thoracic aorta geometry. First, the segmentation process identifies the vessel centerline coordinates following a toroidal path for the curvilinear portion and axial planes for descending aorta. Then, reconstructing oblique planes orthogonal to the centerline direction, it iteratively fits circles inside the vessel cross-section. Finally, regional thoracic aorta dimensions (diameter, volume and length) and shape (vessel curvature and tortuosity) are calculated. A population of 200 normotensive men was recruited. Length, mean diameter and volume differed by 1.2 cm, 0.13 cm and 21 cm(3) per decade of life, respectively. Aortic shape uncoiled with aging, reducing its tortuosity and increasing its radius of curvature. The arch was the most affected segment. In conclusion, non-contrast cardiac CT imaging can be successfully employed to assess thoracic aorta 3D morphometry.

BackgroundThe presence of calcified atherosclerosis in different vascular beds has been associated with a higher risk of mortality. Thoracic aorta calcium (TAC) can be assessed from computed tomography (CT) scans, originally aimed at coronary artery calcium (CAC) assessment. CAC screening improves cardiovascular risk prediction, beyond standard risk assessment, whereas TAC performance remains controversial. However, the curvilinear portion of the thoracic aorta (TA), that includes the aortic arch, is systematically excluded from TAC analysis. We investigated the prevalence and spatial distribution of TAC all along the TA, to see how those segments that remain invisible in standard TA evaluation were affected.Methods and ResultsA total of 970 patients (77% men) underwent extended non-contrast cardiac CT scans including the aortic arch. An automated algorithm was designed to extract the vessel centerline and to estimate the vessel diameter in perpendicular planes. Then, calcifications were quantified using the Agatston score and associated with the corresponding thoracic aorta segment. The aortic arch and the proximal descending aorta, “invisible” in routine CAC screening, appeared as two vulnerable sites concentrating 60% of almost 11000 calcifications. The aortic arch was the most affected segment per cm length. Using the extended measurement method, TAC prevalence doubled from 31% to 64%, meaning that 52% of patients would escape detection with a standard scan. In a stratified analysis for CAC and/or TAC assessment, 111 subjects (46% women) were exclusively identified with the enlarged scan.ConclusionsCalcium screening in the TA revealed that the aortic arch and the proximal descending aorta, hidden in standard TA evaluations, concentrated most of the calcifications. Middle-aged women were more prone to have calcifications in those hidden portions and became candidates for reclassification.

Aging produces a simultaneous thoracic aorta (TA) enlargement and unfolding. We sought to analyze the impact of hypertension on these geometric changes. Non-contrast computed tomography images were obtained from coronary artery calcium scans, including the entire aortic arch, in 200 normotensive and 200 hypertensive asymptomatic men. An automated algorithm reconstructed the vessel in three-dimensions, estimating orthogonal aortic sections along the whole TA pathway, and calculated several geometric descriptors to assess TA morphology. Hypertensive patients were older with respect to normotensive (P<0.001). Diameter and volume of TA ascending, arch and descending segments were higher in hypertensive patients with respect to normotensive (P<0.001) and differences persisted after adjustment for age. Hypertension produced an accelerated unfolding effect on TA shape. We found increments in aortic arch width (P<0.001), radius of curvature (P<0.001) and area under the arch curve (P<0.01) with a concomitant tortuosity decrease (P<0.05) and no significant change in aortic arch height. Overall, hypertension produced an equivalent effect of 2-7-years of aging. In multivariate analysis adjusted for age and hypertension treatment, diastolic pressure was more associated to TA size and shape changes than systolic pressure. These data suggest that hypertension accelerates TA enlargement and unfolding deformation with respect to the aging effect.