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 measurements of aneurysm size obtained after endovascular abdominal aortic aneurysm repair; however, little is known about the variability of these measurements. We evaluated the variability of CT angiographic measurements of aneurysm size obtained after endovascular abdominal aortic aneurysm repair. MATERIALS AND METHODS Thirty CT angiographic data sets were randomly chosen from 91 sets, including preoperative, postoperative, and follow-up CT images. All images were obtained according to a standardized acquisition protocol. On a workstation, three parameters were measured: maximum aneurysm diameter, maximum aneurysm cross-sectional area, and aneurysm volume. All data sets were measured twice by two investigators in a random order. The difference of each pair of measurements was plotted against the mean value. The mean difference and its standard deviation were calculated with a repeatability 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 mL for volume. For observer 2, these figures were 3.0 mm, 219.0 mm(2), and 8.1 mL, respectively. The interobserver repeatability coefficients were 3.9 mm, 236.2 mm(2), and 10.3 mL. CONCLUSION Determination of the repeatability coefficient of aneurysm size measurements obtained after endovascular abdominal aortic aneurysm repair provides a good description of precision.