What Is the Optimal Abdominal Aortic Aneurysm Sac Measurement on CT Images during Follow-up after Endovascular Repair?

Abstract

Purpose To develop a computed tomographic (CT) angiographic postprocessing protocol with two- and three-dimensional measurements for follow-up of patients who underwent endovascular aortic repair. Materials and Methods This HIPAA-compliant institutional review board-approved retrospective study included 159 patients (129 men, 30 women; mean age ± standard deviation, 74.9 years ± 8.2) who underwent 824 CT examinations (median of five examinations per patient; range, two to 14) with unenhanced and arterial -phase imaging performed between September 2004 and March 2015. The largest diameter on the axial plane; coronal, sagittal, and maximal diameter perpendicular to the reconstructed centerline; volume of the abdominal aortic aneurysm sac; and volume from the lowest renal artery to the aortic bifurcation and to the common iliac artery bifurcation were measured. Endoleaks on contrast material-enhanced images were considered the reference standard, and the predictive value of diameter and volume changes was analyzed. Intraclass correlation was used to compare diameters and volumes. Results All diameters and volumes showed excellent correlation (intraclass coefficient, 0.95 and 0.94, respectively). Average interobserver difference for diameters and volumes was 2%-3% and 4%-12%, respectively. Endoleaks were observed in 80 (50%) of 159 patients (59 [74%] at initial and 21 [26%] at later CT angiography). New endo-leaks were associated with increased aneurysm size measured as the largest diameter on the axial plane (P = .04) and perpendicular to the centerline (P = .01), and volume was measured from the lowest renal artery to the aortic bifurcation (P = .03) and to the common iliac artery bifurcation (P = .01). With a 5% size threshold, sensitivity and specificity for detection of endoleaks was optimal for centerline diameter (64.3% and 81.7%, respectively) and volume from the lowest renal artery to the common iliac artery bifurcation (57.1% and 63.5%). Conclusion The maximal diameter and volume of an abdominal aortic aneurysm sac can be used for temporal monitoring after endovascular aortic repair, with excellent correlation and interobserver agreement. An increase in the centerline diameter and volume from the lowest renal artery to the iliac bifurcation were the most sensitive criteria for detecting endoleaks. RSNA, 2017 Online supplemental material is available for this article.

Photon-Counting Detector CT Angiography for Endoleak Detection After Endovascular Aortic Repair

“…The optimal number of scan phases required for imaging after EVAR remains a contentious topic in the literature. Some studies have suggested that a noncontrast scan alone is adequate to assess size changes of the aneurysmal sac and predict significant endoleaks 38 . Others have recommended the use of VNC and late delayed phase images obtained from a single dual-energy CT acquisition 12,39 .…”

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

“…Although AAA and ILT volume, which rely on segmentation of the lumen and outer wall for quantification, may have a future role in AAA management [13,39,40], AAA maximal diameter is presently the primary parameter driving clinical decisions. Manual measurement of diameter from either 3D volumetric imaging modalities or US has limited reproducibility [1,8,32] and growth rates measured by different readers can differ substantially and may affect clinical management [29].…”

Too Big or Not Too Big…?

“…In their study, Yafawi et al 1 have identified a correlation between volume increase and migration, but the causal relationship remains undetermined. Boos et al 5 have also demonstrated a linear relationship between volume increase and the presence of endoleaks (type IeIV). However, the clinical consequences of those endoleaks were not reported and, with a 5% threshold the sensitivity and specificity of this criterion were lower than the maximum diameter in centre line.…”