Three-Dimensional Ultrasound Evaluation of Small Asymptomatic Abdominal Aortic Aneurysms

Abstract

Non-invasive and reproducible size measurements that correlate well with computed tomography (CT) are desirable in the management of small abdominal aortic aneurysms (AAA). Three dimensional ultrasound (3D-US) technology may reduce inaccuracy because of variations in orientation of the image planes and axis. This study aimed to determine any differences in paired size estimation associated with three 3D-US derived methods using 3D-CT as the gold standard. When CTA was not available, the patients were enrolled anyway to assess 3D-US reproducibility in terms of agreement between two physicians. In the period from 1 March 2013 to 27 February 2014, consecutive patients with a small AAA, <5.5cm for men and <5.2cm for women, underwent 3D-US examination and three AAA size measures were obtained: dual plane diameter, diameter perpendicular to the residual sac's centreline and a partial volume. In all, 122 consecutive US examinations were performed. Patients were excluded because of inadequate AAA size (n=11) and for technical reasons (n=11). Thus, 100 patients (F/M; 20/80) with a median maximum AAA diameter of 46 (range 31-55) mm were analysed. The mean US dual plane diameter and the 3D-US centreline diameter were 2.6mm and 1.8mm smaller than the mean 3D-CT centreline diameter, respectively (p=.003). The inter-observer reproducibility coefficient was 3.7mm for the US dual plane diameter and 3.2mm for the 3D-US centreline diameter (p=0.222). For the partial volume, the reproducibility was 8-12%, corresponding to a diameter variability of ±3mm. The median time used for post-processing of the 3D-US acquisition was 72 (range 46-108) seconds per examination. 3D-US demonstrated an acceptable reproducibility and a good agreement with 3D-CT, and has the potential to improve future AAA management through more reliable ultrasound guided size estimates.