Internal carotid arterial stenosis: CT angiography with volume rendering

PURPOSE: To determine the reliability of helical computed tomography (CT) w ith volume rendering for evaluation of internal carotid arterial stenosis. MATERIALS AND METHODS: In 22 patients, 44 carotid arteries were evaluated w ith helical CT and selective conventional angiography. CT data were display ed on volume-rendered and maximum intensity projection (MIP) images. Stenos es were measured separately on axial, volume-rendered, and MIP images and o n conventional angiograms. Each artery was then graded as having no stenosi s, mild (<30%) stenosis, moderate (30%-70%) stenosis, severe (>70%) stenosi s, near occlusion, or Occlusion. RESULTS: One case of stenosis was not assessable at axial CT because of an inappropriate scanning plane; four cases were not assessable at MIP CT beca use 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 angiograph y and helical CT were good. Axial, volume-rendered, and MIP images enabled correct classification of stenosis in 88%, 89%, and 90% of arteries, respec tively. CT with volume rendering was slightly more sensitive for determinin g candidates for endarterectomy (ie, those with >70% stenosis and near occl usion); sensitivity was 100% and specificity, 92%. CONCLUSION: CT angiography with volume rendering enabled accurate evaluatio n of carotid disease, even when dense calcifications were present. However, no definite advantage over currently available techniques for CT measureme nt of stenosis severity was found.