Maximum Diameter of Native Abdominal Aortic Aneurysm Measured by Angio-Computed Tomography

Abstract

Background: Computed tomography angiography (CTA) is the reference technique for the measurement of native maximum abdominal aortic aneurysm (AAA) diameter when surgery is being considered. However, there is a wide choice available for the methodology of maximum AAA diameter measurement on CTA, and to date, no consensus has been reached on which method is best. We analyzed clinical decisions based on these various measures of native maximum AAA diameter with CTA, then analyzed their reproducibility and identified the method of measurement yielding the highest agreement in terms of patient management. Materials and Methods: Three sets of measures in 46 native AAA were obtained, double-blind by three radiologists (J, S, V) on orthogonal planes, curved multiplanar reconstructions, and semi-automated-software, based on the AAA-lumen centerline. From each set, the clinical decision was recorded as follows: "Follow-up" (if all diameters <50 mm), "ambiguous" (if at least one diameter <50 mm AND at least one ≥50 mm) or "Surgery " (if all diameters ≥50 mm). Intra- and interobserver agreements in clinical decisions were compared using the weighted Kappa coefficient. Results: Clinical decisions varied according to the measurement sets used by each observer, and according to intra and interobserver (lecture#1) reproducibility. Based on the first reading of each observer, the number of AAA proposed for surgery ranged from 11 to 24 for J, 5 to 20 for S, and 15 to 23 for V. The rate of AAAs classified as "ambiguous" varied from 11% (5/46) to 37% (17/46).The semi-automated method yielded very good intraand interobserver agreements in clinical decisions in all comparisons (Kappa range 0.83–1.00). Conclusion: The semi-automated method seems to be appropriate for native AAA maximum diameter measurement on CTA. In the absence of AAA outer-wallbased software more robust for complex AAA, clinical decisions might best be made with diameter values obtained using this technique.

Editor's Choice – European Society for Vascular Surgery (ESVS) 2019 Clinical Practice Guidelines on the Management of Abdominal Aorto-iliac Artery Aneurysms

“…113 Many of the same issues concerning measurement by US apply to CT measurement, for example axial versus orthogonal centreline diameters, changes with the cardiac cycle and details of calliper placement. 114,115 When applying predefined methodologies, intra-observer reproducibility can be within the clinically accepted range (AE5 mm) in 90% AAA measurements, but the inter-observer reproducibility is poor, with 87% comparisons being outside AE 5 mm. 114 This variability is of particularly high clinical significance, since the number of patients considered for AAA repair, based on a diameter threshold, may vary from 11% to 24%, 5%e20%, and 15%e23% for three different radiologists.…”

Artificial intelligence assistance improves reporting efficiency of thoracic aortic aneurysm CT follow-up

“…A careful follow-up monitoring of aneurysm morphology is crucial; contrast-enhanced electrocardiogram-gated (ECG-gated) CT is the imaging modality of choice [10]. Nevertheless, the considerable error susceptibility of aortic diameter measurements is widely described [10][11][12][13][14][15]: The comparison of follow-up exams requires measurements at exactly the same anatomic landmark positions and any diameter measurement crucially depends on the correct alignment of multiplanar reconstruction orthograde to the aortic centerline. Furthermore, pulsation artefacts and the elasticity of the aorta can hamper the assessment even in ECG-gated CTs [16].…”

Computer-aided quantification of non-contrast 3D black blood MRI as an efficient alternative to reference standard manual CT angiography measurements of abdominal aortic aneurysms

“…More importantly, the potential accuracy of automated analysis approaches, from either CTA or black blood MRI, has not been thoroughly investigated. The present paper addresses both of these limitations in the context of non-contrast black blood MRI, suggesting that expedient computer-aided analysis indeed provides accurate anatomic measurements for AAA surveillance [8,32,33]. Segmentation of both the AAA lumen and outer wall from non-contrast black blood MRI is more challenging than from CTA, in part due to reduced contrast between the aneurysm and peri-aortic tissues, potential motion artifacts given the longer scan time required (compared to seconds for CTA), and incomplete suppression of flowing blood necessary to delineate the vessel lumen.…”