Observer variation in vascular CT measurements of the abdominal aorta

Aim: To assess the inter-observer variation between a radiographer and radiologist when performing CT measurement of the abdominal aorta before endovascular aortic aneurysm repair (EVAR). Methods: A total of 30 consecutive patients who were considered anatomically suitable for EVAR had aortic measurements performed independently by a vascular radioogist and then by a radiographer training vascular and CT imaging. All measurements were performed on a computer workstation using electronic callipers, each patient had 12 anatomical sites evaluated (eight diameters, four vessel lengths). Statistical analysis was performed by the computer package SPSS for Windows 11.01. Results: Of the 30 patients, mean difference in measurements between observers was 2.3 mm ± 1.2 mm and 6.0 mm ± 6.4 mm for diameter and vessel length measurements, respectively. Two hundred and seven (86%) diameter measurements were ≤2 mm of each other and 233 (97%) were within ≤5 mm. Eighty-two (57%) length measurements were within ≤5 mm, and 100 (83%) within 10 mm or less. Widest variation existed for measurements of common iliac diameter and aortic neck length, where coefficients of variance were 38.2 (95% CI 35.7-41.0) and 40.0 (95% CI 36.2-44.6), respectively. Conclusion: A good level of agreement exists between a trained radiographer and radiologist when comparing vascular CT measurements of the aorta. It is technically feasible for a radiographer to perform these measurements, and improvements in variability may be achieved from a more standardised technique and automated vessel analysis software. Further research is required to establish the overall variability between different observer types when undertaking vascular CT measurements.