Observer variation in vascular CT measurements of the abdominal aorta

Abstract 

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 2.3mm±1.2mm and 6.0mm±6.4mm for diameter and vessel length measurements, respectively. Two hundred and seven (86%) diameter measurements were ≤2mm of each other and 233 (97%) were within ≤5mm. Eighty-two (57%) length measurements were within ≤5mm, and 100 (83%) within 10mm 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.

Keywords: Abdominal aortic aneurysm, Computed tomography, Quantification, Observer variation