Imaging surveillance after open aortic repair: a feasibility study of three-dimensional growth mapping

Abstract

Objectives: Confident growth assessment during imaging follow-up is often limited by substantial variability of diameter measurements and the fact that growth does not always occur at standard measurement locations. There is a need for imaging-based techniques to more accurately assess growth. In this study, we investigated the feasibility of a three-dimensional aortic growth assessment technique to quantify aortic growth in patients following open aortic repair.

Methods: Three-dimensional aortic growth was measured using vascular deformation mapping (VDM), a technique which quantifies the localized rate of volumetric growth at the aortic wall, expressed in units of Jacobian (J) per year. We included 16 patients and analysed 6 aortic segments per patient (96 total segments). Growth was assessed by 3 metrics: clinically reported diameters, Jacobian determinant and targeted diameter re-measurements.

Results: VDM was able to clearly depict the presence or absence of localized aortic growth and allows for an assessment of the distribution of growth and its relation to anatomic landmarks (e.g. anastomoses, branch arteries). Targeted diameter change showed a stronger and significant correlation with J (r = 0.20, P = 0.047) compared to clinical diameter change (r = 0.15, P = 0.141). Among 20/96 (21%) segments with growth identified by VDM, growth was confirmed by clinical measurements in 7 and targeted re-measurements in 11. Agreement of growth assessments between VDM and diameter measurements was slightly higher for targeted re-measurements (kappa = 0.38) compared to clinical measurements (kappa = 0.25).

Conclusions: Aortic growth is often uncertain and underappreciated when assessed via standard diameter measurements. Three-dimensional growth assessment with VDM offers a more comprehensive assessment of growth, allows for targeted diameter measurements and could be an additional tool to determine which post-surgical patients at high and low risk for future complications.

Keywords: Aortic growth; Imaging surveillance; Open aortic aneurysm repair; Thoracic aortic aneurysm; Vascular deformation mapping.

Figure 1:

Patient selection flow chart. CT: computed tomography; ECG: electrocardiogram.

Figure 2:

Schematic representation of the steps involved in the vascular deformation mapping analysis (A), and the definition of the 6 aortic segments used for analysis of growth (B). (1) Ascending aorta: sinotubular junction to superior border of right pulmonary artery, (2) Proximal Arch: right pulmonary artery to distal innominate artery, (3) Mid-arch: innominate artery to distal left subclavian artery (LSA), (4) Proximal Descending: LSA to 2 cm distal to LSA, (5) Mid-descending: 2 cm distal to LSA to 10 cm distal to LSA and (6) Distal Descending: 10 cm distal to LSA to coeliac artery. 3D: three-dimensional; CT: computed tomography.

Figure 3:

A representative case of an ascending aortic repair case with detected growth (patient 1) is shown with vascular deformation mapping and corresponding diameter measurements (A), as well as comparison of growth measurements along the length of the aorta (B). Grey-shading denotes range of measurements defined as no growth. CT: computed tomography.

Figure 4:

A representative case of an ascending aortic repair without detected growth (patient 5) is shown with corresponding vascular deformation mapping and corresponding diameter measurements (A), as well as comparison of growth measurements along the length of the aorta (B). Grey-shading denotes range of measurements defined as no growth. CT: computed tomography.

Figure 5:

A representative case of a descending thoracic aortic repair with detected growth (patient 4) is shown with corresponding vascular deformation mapping and corresponding diameter measurements (A), as well as comparison of growth measurements along the length of the aorta (B). Grey-shading denotes range of measurements defined as no growth. CT: computed tomography.

Figure 6:

Correlation analysis and agreement of growth assessment between vascular deformation mapping Jacobian-based assessment and targeted re-measurement (A) and clinical measurements (B). VDM: vascular deformation mapping.