Prospective Evaluation of Suspected Stenoocclusive Disease of the Intracranial Artery: Combined MR Angiography and CT Angiography Compared with Digital Subtraction Angiography

BACKGROUND AND PURPOSE: MR angiography is primarily and increasingly used to assess intracranial arterial stenoocclusion. However, MR angiography can cause overestima-tion of stenosis. Although CT angiography is accurate, it has limitations. Our purpose was to determine whether the accuracy of combined MR angiography and CT angiography is equal to that of digital subtraction angiography (DSA) in measuring stenosis and detecting major intracranial arterial occlusion. METHODS: CT angiography and intraarterial DSA were prospectively performed in 18 patients with suspected intracranial stenoocclusive disease, as revealed with MR angiography. Before DSA, two reviewers independently assessed MR intracranial angiograms. Subsequently, they assessed CT angiograms with MR angiograms. Results were compared with DSA results. The degree of stenoocclusion was categorized; stenosis of 50 % or more indicated stenoocclusive disease. After the blinded study, two radiologists retrospectively reviewed the angiographic findings. RESULTS: Stenoocclusive disease was identified in 18 of 198 intracranial arteries at DSA. MR angiography had a sensitivity of 92%, a specificity of 91%, and an accuracy of 91 % for the identification of stenosis of 50 % or more; the addition of CT angiography yielded values of 100%, 99%, and 99%, respectively. Stenotic grades with combined CT angiography and MR angiography agreed with those of DSA in 98 % of cases. In the retrospective study, CT angiography did not always correctly delineate arterial lumina with circumferential calcifica-tion and cavernous portions of the internal carotid artery. CONCLUSION: In this investigation, the evaluation of suspected stenoocclusive diseases in major intracranial arteries, the accuracy of combined MR angiography and CT angiography is equal to that of DSA in most cases. Atherosclerotic narrowing of the major intracranial arteries (carotid siphon; anterior, middle, or posterior cerebral arteries; vertebral artery; basilar artery) is associated with a risk of stroke (1). Results of th