Inter- and intraobserver variability of CT measurements obtained after endovascular repair of abdominal aortic aneurysms

OBJECTIVE. important decisions are made on the basis of CT angiographic mea surements of aneurysm size obtained after endovascular abdominal aortic ane urysm repair; however, little is known about the variability of these measu rements. We evaluated the variability of CT angiographic measurements of an eurysm size obtained after endovascular abdominal aortic aneurysm repair. MATERIALS AND METHODS. Thirty CT angiographic data sets were randomly chose n from 91 sets, including preoperative, postoperative, and follow-up CT ima ges. All images were obtained according to a standardized acquisition proto col. On a workstation, three parameters were measured: maximum aneurysm dia meter, maximum aneurysm cross-sectional area, and aneurysm volume. All data sets were measured twice by two investigators in a random order. The diffe rence of each pair of measurements was plotted against the mean value. The mean difference and its standard deviation were calculated with a repeatabi lity coefficient. RESULTS. The intraobserver repeatability coefficient for observer 1 was 3.8 mm for diameter, 201.7 mm(2) for cross-sectional area, and 5.6 mt for volu me. For observer 2, these figures were 3.0 mm, 219.0 mm(2), and S.1 mt, res pectively. The interobserver repeatability coefficients were 3.9 mm, 236.2 mm(2), and 10.3 mt. CONCLUSION. Determination of the repeatability coefficient of aneurysm size measurements obtained after endovascular abdominal aortic aneurysm repair provides a good description of precision.