Introduction: To determine the diagnostic agreement between manual and semi-automated vessel analysis software measurements of extracranial internal carotid artery (ICA) steno-occlusive disease on CT-angiography (CTA).
Methods: We studied consecutive patients with acute cerebral ischemia who were admitted (01/2012 to 12/2012) to our academic stroke center and underwent CTA for routine evaluation of stroke. NASCET-type percent stenosis was independently assessed on axial CTA source images by 1) manual caliper measurements and, 2) the semi-automated vessel analysis software syngo®.via (Siemens Healthcare, Germany) that provides area stenosis estimates. To correspond to clinically relevant NASCET strata, all stenosis measurements were stratified into ranges: normal, 1-49%, 50-69%, 70-99%, and occlusion.
Results: A total of 330 patients (age 72±12yrs; 58% men; median NIHSS 4, interquartile range 8) provided 647 vessel pairs for comparative analysis. Manual caliper measurements revealed 50-69% stenosis in 29, 70-99% stenosis in 6 and occlusion in 34 internal carotid arteries, while semi-automated vessel analysis detected 50-69% stenosis in 27, 70-99% stenosis in 14 and occlusion in 34 internal carotid arteries (p=0.003). Bland-Altman analysis showed a mean difference of 1.55% in the degree of stenosis between both methods with lower and upper limits of agreement of -16.7 to 19.8%.
Conclusions: Although we found an overall good agreement between both stenosis grading methods, the semi-automated vessel software analysis seems to overcall the stenosis in severe ranges when compared with manual caliper measurements.