Four-dimensional analysis of aortic root motion in normal population using retrospective multiphase computed tomography

Abstract

Aortic root motion is suspected to contribute to proximal aortic dissection. While motion of the aorta in 4 dimensions can be traced with real-time imaging, displacement and rotation in quantitative terms remain unknown. The hypothesis was to slow feasibility of quantification of 3-dimensional aortic root motion from dynamic CT imaging. Dynamic CT images of 40 patients for coronary assessment were acquired using a dynamic protocol. Scans were ECG-triggered and segmented in 10 time-stepped phases (0%-90%) per cardiac cycle. With identification of the sino-tubular junction (STJ) a patient-specific coordinate system was created with the Z-axis (out-of-plane) parallel to longitudinal direction. The left and right coronary ostia were traced at each time-step to quantify downward motion in reference to the STJ plane, motion within the STJ plane (in-plane), and the degree of rotation. Enrolled individuals had an age of 65 ± 12, and 14 were male (35%). The out-of-plane motion was recorded with the largest displacement of 10.26 ± 2.20 and 8.67 ± 1.69 mm referenced by left and right coronary ostium, respectively. The mean downward movement of aortic root was 9.13 ± 1.86 mm. The largest in-plane motion was recorded at 9.17 ± 2.33 mm and 6.51 ± 1.75 mm referenced to left and right coronary ostium, respectively. The largest sino-tubular junction in-plane motion was 7.37 ± 1.96 mm, and rotation of the aortic root was 11.8 ± 4.60⁰. In-vivo spatial and temporal displacement of the aortic root can be identified and quantified from multiphase ECG-gated contrast-enhanced CT images. Knowledge of normal 4D motion of the aortic root may help understand its biomechanical impact in patients with aortopathy and pre- and post-surgical or transcatheter aortic valve replacement.