THE EFFECT OF ANGIOGRAPHIC TECHNIQUE AND IMAGE QUALITY ON THE REPRODUCIBILITY OF MEASUREMENT OF CAROTID STENOSIS AND ASSESSMENT OF PLAQUE SURFACE-MORPHOLOGY

We studied the reproducibility of measurement of carotid stenosis and assessment of plaque surface morphology on 1001 angiograms from a cons ecutive series of patients entered into the European Carotid Surgery T rial. Inter-observer agreement (Kappa statistic, 95% confidence interv al (CI)) for categorization of carotid stenosis, as 0-29%, 30-69 % or 70-99 % was good (0.68, 0.63-0.73) on 789 conventional or digitally su btracted selective angiograms, and good (0.64, 0.54-0.75) on 174 conve ntionally and digitally subtracted aortic arch injection angiograms, b ut was poor (0.29, 0.02-0.80) on 29 intravenous digital subtraction an giograms. Inter-observer agreement did not vary with the method of ima ge acquisition of arterial angiograms, but was dependent on the qualit y of visualization of the stenosis: kappa = 0.73 (0.67-0.79) for good quality angiograms vs. 0.54 (0.44-0.64) for poor quality angiograms. I nter-observer agreement for assessment of plaque surface morphology wa s moderate (kappa 0.4-0.6) and did not vary with type of angiography o r method of image acquisition. However, ulceration was reported most f requently on selective angiograms and on those angiograms on which the quality of visualization of the stenosis was good. We conclude that t he reproducibility of measurement of carotid stenosis and the assessme nt of plaque surface morphology vary depending on the type of angiogra phy and the quality of visualization of the stenosis, This should be t aken into account when validating noninvasive methods of imaging the c arotid bifurcation.