Ultrasound-determined diameter measurements are more accurate than axial computed tomography after endovascular aortic aneurysm repair

Abstract

This study evaluated the correlation of ultrasound (US)-derived aortic aneurysm diameter measurements with centerline, three-dimensional (3-D) reconstruction computed tomography (CT) measurements after endovascular aortic aneurysm repair (EVAR). Concurrent CT and US examinations from 82 patients undergoing post-EVAR surveillance were reviewed. The aortic aneurysm diameter was defined as the major axis on the centerline images of 3-D CT reconstruction. This was compared with US-derived minor and major axis measurements, as well as with the minor axis measurement on the conventional axial CT images. Correlation was evaluated with linear regression analyses. Agreement between different imaging modalities and measurements was assessed with Bland-Altman plots. The correlation coefficients from linear regression analyses were 0.92 between CT centerline major and US minor measurements, 0.94 between CT centerline major and US major measurements, and 0.93 between CT minor and centerline major measurements. Bland-Altman plots showed a mean difference of 0.11 mm between US major and CT centerline measurements compared with 5.38 mm between US minor and CT centerline measurements, and 4.25 mm between axial CT minor and centerline measurements. This suggested that, compared with axial CT and US minor axis measurements, US major axis measurements were in better agreement with CT centerline measurements. Variability between major and minor US and CT centerline diameter measurements was high (standard deviation of difference, 4.27-4.84 mm). However, high variability was also observed between axial CT measurements and centerline CT measurements (standard deviation of difference, 4.36 mm). The major axis aneurysm diameter measurement obtained by US imaging for surveillance after EVAR correlates well and is in better agreement with centerline 3-D CT reconstruction diameters than axial CT.