RESUMO
OBJECTIVE: Aortic computed tomography angiography (CTA) examination with electrocardiography gating is becoming the clinical routine image acquisition protocol for diagnosis and intervention planning. To minimize motion artifact, the images are reconstructed in the diastolic phase of the cardiac cycle. The aim of our study was to quantify aortic strain in an elderly nonaneurysmatic patient cohort and to identify the phases of the R-R cycle that correspond to the minimal and maximal aortic diameters. The quantification of aortic strain may enable the improvement of intervention planning and the introduction of more effective dose-saving protocols for CTA scans. METHODS: We assessed CTA images of 28 patients (14 men; mean age, 74 years). Aortic calcium score was calculated on native images. Angiography images were reconstructed in equally spaced 10 phases of the R-R cycle. After semiautomatic centerline analysis, we measured the cross-sectional areas in each of the 10 phases at 9 specific segments between the ascending aorta and the common iliac bifurcation representing the attachment sites of thoracic and abdominal stent grafts. Area-derived effective diameter, pulsatility (Amax - Amin), and strain [(Amax - Amin)/Amin] were calculated. Repeated measurements were taken to evaluate inter-reader and intrareader reproducibility (10-10 patients each). RESULTS: A total of 4320 measurements were performed. We found significant difference between diastolic and systolic diameters (DD,Z0 = 33.2, DS,Z0 = 34.4; P < .001). Pulsatility values of the vessel diameters were 1.0 to 1.1 mm in the thoracic aorta, 0.7 to 0.9 mm in the abdominal aorta, and 0.5 to 0.6 mm in the common iliac arteries. Negative, moderate correlations were found between aortic strain and age (r = -0.586; P = .001), aortic strain and plaque area (r = -0.429; P = .026), and age and body mass index (r = -0.412; P = .029). We found positive, moderate correlation between age and plaque area (r = 0.594; P = .001). The aortic pulsatility curve has a positive extreme at 30% and a negative extreme at 90% of the R-R cycle throughout the aorta. Lin concordance coefficients were 0.987 for inter-reader and 0.994 for intrareader correlations. CONCLUSIONS: Aortic strain can be reliably quantified on electrocardiography-gated CTA images. Pulsatility of the aorta can be substantial in the thoracic aortic segments of young patients; therefore, the routine use of systolic images is not recommended. In addition, we demonstrated that images at 30% of the heart cycle correspond to the largest diameter of the aorta.
