CT angiographic analysis of carotid artery stenosis: comparison of manual assessment, semiautomatic vessel analysis, and digital subtraction angiography

Abstract

Background and purpose: To compare multisection CT angiography (CTA) analyzed with source/maximum intensity projection (MIP) images as well as semiautomated vessel analysis software with intra-arterial digital subtraction angiography (DSA) in detection and grading of carotid artery bifurcation stenosis.

Methods: Consecutive patients with sonography evidence of a marked internal carotid artery stenosis underwent both carotid CTA and DSA (37 patients, 73 vessels). In CTA, the grade of stenosis was determined using axial source and MIP images as well as vessel analysis. The scans were blind-analyzed by 2 neuroradiologists using the NASCET criteria.

Results: Correlation of CTA source/MIP images versus DSA estimates of stenosis (R = 0.95) was higher than for the vessel analysis method versus DSA (R = 0.89). Compared with DSA, CTA source/MIP images underestimated high (78.2% versus 86.4%, P < .05) and moderate grades of stenosis (57.3% versus 63.1%, P < .05) to a lesser extent than the vessel analysis method (68.5% versus 83.5% and 51.8% versus 63.1%, P < .05). For a high-grade stenosis, sensitivity and specificity of source/MIP image CTA were 75% and 96%, respectively, whereas for the vessel analysis method, they were 47% and 96%, respectively. For moderate stenosis, the source/MIP image CTA sensitivity and specificity were 88% and 82%, respectively, and for vessel analysis method, 62% and 82%, respectively. CTA detected all 4 occlusions.

Conclusion: In evaluation of carotid stenosis, CTA provides an adequate, less invasive alternative with a high correlation to conventional DSA, though it tends to underestimate clinically relevant grades of stenosis. Its accuracy is not improved by semiautomated analysis. The data support the use of CTA in confirming carotid occlusion.

Fig 1.

Measurement of the internal carotid artery stenosis in CTA axial images according to NASCET. A, Maximal stenosis in left ICA. B, Normalized vessel diameter. The reference point was chosen so that diameters are the same over a distance.

Fig 2.

A, Stenosis measurement levels marked to CTA MIP images according to NASCET. Dental filling artifacts are shown. B, Vessel analysis method in determination of the grade of stenosis. Dental filling artifacts are shown. C, DSA image.

Fig 3.

Scatterplot of degrees of stenosis in CTA (A) versus DSA (B) with regression line and 95% confidence intervals.

Fig 4.

Histogram of average degrees within different categories of stenosis by method of assessment.

Fig 5.

Poststenotic collapse. A, Maximal stenosis in left ICA (big arrow). Calcification behind the open lumen. The right ICA is normal (small arrow). B, The distal left ICA (big arrow) remains collapsed. Normal right ICA (small arrow). C, MIP image of the left ICA. D, DSA image of the left ICA.

Fig 6.

Underestimation of stenosis in DSA. A, An axial MIP image from the left ICA stenosis graded severe by CTA (arrow). According to the vessel analysis method (B, C) the stenosis is 77%. In DSA, the maximum stenosis is 50% (D). In surgery, the stenosis turned out to be severe.