A comparison of radiographers and radiologists in CT based measurements of abdominal aortic aneurysms

Aim: To evaluate the variability of CT AAA measurements undertaken by radiologists and radiographers. Methods: 19 Observers (4 radiologists, 15 radiographers) were invited to independently measure maximum aneurysm diameter (Dmax) on ten CT scans. Each CT scan was presented randomly to each observer; four were duplicates testing intra-observer variability. All measurements were undertaken from axial CT images using electronic callipers, all observers were blinded to any previous measurements. Both the slice number and the maximum AAA diameter (in any plane) were recorded. Results: Intra-observer variability was lower for radiographers with a mean paired difference of -0.18 ± 2.6. mm compared to -2.1 ± 3.5. mm (P= 0.054). Inter-observer variability within each observer group was comparable, radiographers 0.1 ± 5.0. mm; radiologists -0.1 ± 3.1. mm (P= 0.680). When directly comparing between the two groups mean difference was -2.0 ± 4.0. mm with 43% of paired measurements ≤2. mm or less and 78% ≤5. mm. Slice selection was less variable between the two groups with 88% of repeat radiographer measurements within ±1 slice and 91% of radiologists measurements with ±1 slice (P= 0.228). Conclusion: The accuracy of radiographers in performing AAA CT measurements is encouraging. Variability exists for both professions, and in some instances may be clinically significant. Observers should be aware of measurement variability issues and have an understanding of the factors responsible. Careful and repeat measurements of AAAs around 5.5. cm are recommended in order to define treatment.