Internal carotid arterial stenosis: CT angiography with volume rendering

To determine the reliability of helical computed tomography (CT) with volume rendering for evaluation of internal carotid arterial stenosis.

In 22 patients, 44 carotid arteries were evaluated with helical CT and selective conventional angiography. CT data were displayed on volume-rendered and maximum intensity projection (MIP) images. Stenoses were measured separately on axial, volume-rendered, and MIP images and on conventional angiograms. Each artery was then graded as having no stenosis, mild (< 30%) stenosis, moderate (30%-70%) stenosis, severe (> 70%) stenosis, near occlusion, or occlusion.

One case of stenosis was not assessable at axial CT because of an inappropriate scanning plane; four cases were not assessable at MIP CT because of mural calcifications. All carotid arteries were assessable on volume-rendered images despite no depiction of the residual lumen at the site of narrowing in three cases of near occlusion. Correlations between angiography and helical CT were good. Axial, volume-rendered, and MIP images enabled correct classification of stenosis in 88%, 89%, and 90% of arteries, respectively. CT with volume rendering was slightly more sensitive for determining candidates for endarterectomy (i.e., those with > 70% stenosis and near occlusion); sensitivity was 100% and specificity, 92%.

CT angiography with volume rendering enabled accurate evaluation of carotid disease, even when dense calcifications were present. However, no definite advantage over currently available techniques for CT measurement of stenosis severity was found.