Validation of a new standardized method to measure proximal aneurysm neck angulation

Abstract

This study presented and validated a new standardized method for the measurement of the aortic angulation in patients with abdominal aortic aneurysms (AAA) and quantified the observer variability. A standardized method to quantify aortic angulation was introduced. To measure aortic angulation, a center lumen line (CLL) of the aorta was made, and a three-dimensional (3D) aortic reconstruction was obtained. The 3D reconstruction was turned 360 degrees perpendicular to the CLL in the middle of the flexure. The sharpest angle of the CLL was considered the true angle of the aortic axis. The computed tomography angiography data sets of 20 patients scheduled for endovascular aneurysm repair (EVAR) were obtained. The angles between the suprarenal aorta and the aneurysm neck (alpha) and between the aneurysm neck and sac (beta) were measured. Two observers independently measured the angles. Differences of each pair of measurements were plotted against their mean and intraobserver and interobserver variabilities were calculated according to Bland and Altman. The intraobserver mean difference for angle alpha was -0.2 degrees (-0.5%), with a repeatability coefficient (RC) of 6.4 degrees (20.2%), and 0.6 degrees (1.4%) for angle beta, with a RC of 6.2 degrees (13.4%). The interobserver mean difference for angle alpha was -1.5 degrees (-4.5%), with a RC of 6.9 degrees (22.0%), and -0.2 degrees (-0.4%) for angle beta, with a RC of 7.4 degrees (16.0%). No significant differences were observed between the observers. The presented technique to objectively quantify the angulation of the aneurysm neck is easy to perform and reliable. This method showed good intraobserver and interobserver variability and should therefore be the standard when measuring and reporting aortic angulation.