Angiographic correlation of CT calcification in the carotid siphon

BACKGROUND AND PURPOSE: Calcification in the coronary arteries has been cor related with significant vessel stenosis. The predictive value of calcifica tion within the carotid siphon has not been characterized; however, stenosi s in the carotid siphon is potentially important in determining management of patients with ipsilateral carotid bifurcation stenosis. The purpose of t his study was to determine optimal parameters for assessing carotid siphon calcification on head CT scans and to compare the CT findings with angiogra phic results. METHODS: We performed a retrospective review of patients referred for diagn ostic carotid arteriography. Those patients who also had undergone a head C T study at our institution were selected. The CT scans and angiograms of 64 patients (128 vessels) were reviewed. Carotid siphon calcification on CT s cans was characterized on brain and bone windows as mild, moderate, or seve re. Comparison was then made with angiographic findings. RESULTS: The sensitivity and specificity of CT for depicting greater than 5 0% angiographic stenosis in the carotid siphon were 86% and 98%, respective ly, for bone windows and 100% and 0%, respectively, for brain windows. The positive predictive value (PPV) for a stenosis of greater than 50% as evide nced by severe calcification was 86% on bone windows and 11% on brain windo ws. The PPV for mild and moderate calcification on bone windows was 2.5% an d 0%, respectively. CONCLUSION: Severe CT calcification in the carotid siphon as characterized on bone windows correlates with a carotid siphon stenosis of greater than 5 0% as determined angiographically. Therefore, the identification of severe calcification offers a potential noninvasive method for identifying stenosi s of the carotid siphon. This information may be essential in determining m anagement and prognosis for patients with carotid bifurcation stenosis.