VASCULAR AND INTERVENTIONAL RADIOLOGYT horacic aortic aneurysm (TAA) is common and is increasing in prevalence worldwide, with approximately 3% of patients older than 50 years having a dilated thoracic aorta (1-3) and recommended to undergo imaging surveillance (4). Most patients with TAA have an indolent disease course, with aortic growth occurring either slowly or not at all over a period of years or decades (5). However, life-threatening complications, such as aortic dissection and rupture, can occur in otherwise asymptomatic patients at presurgical aneurysm sizes (6,7), emphasizing the need for better techniques with which to assess disease progression, inform surgical candidacy, and predict complications. A fundamental limitation to improved management of TAA is the lack of image analysis techniques with which to accurately assess aortic growth.Current assessment techniques are based on measurements of maximal aortic diameter. However, the degree of variability associated with aortic diameter measurements (within 1-5 mm despite optimal measurement technique) frequently prevents confident assessment of disease progression at typical TAA growth rates (,1 mm per year) (8-11). Also, diameter measurements are inherently two dimensional and are performed in fixed anatomic locations; thus, they are unable to capture the three-dimensional (3D) nature of TAA growth.To overcome these limitations, prior research has described the feasibility of a medical image analysis technique, termed vascular deformation mapping (VDM), in 3D assessment of aortic growth using deformable image registration techniques (12,13). This approach uses high Background: Aortic diameter measurements in patients with a thoracic aortic aneurysm (TAA) show wide variation. There is no technique to quantify aortic growth in a three-dimensional (3D) manner.Purpose: To validate a CT-based technique for quantification of 3D growth based on deformable registration in patients with TAA.
Materials and Methods:Patients with ascending and descending TAA with two or more CT angiography studies between 2006 and 2020 were retrospectively identified. The 3D aortic growth was quantified using vascular deformation mapping (VDM), a technique that uses deformable registration to warp a mesh constructed from baseline aortic anatomy. Growth assessments between VDM and clinical CT diameter measurements were compared. Aortic growth was quantified as the ratio of change in surface area at each mesh element (area ratio). Manual segmentations were performed by independent raters to assess interrater reproducibility. Registration error was assessed using manually placed landmarks. Agreement between VDM and clinical diameter measurements was assessed using Pearson correlation and Cohen k coefficients.Results: A total of 38 patients (68 surveillance intervals) were evaluated (mean age, 69 years 6 9 [standard deviation]; 21 women), with TAA involving the ascending aorta (n = 26), descending aorta (n = 10), or both (n = 2). VDM was technically successful in 35 of 38 (92%) pati...