Objective: The purpose of this study was to evaluate the efficacy of circle of Willis CT angiography with shaded-surface display in the detection and assessment of suspected intracranial aneurysms.
Materials and methods: Twenty-three patients who had clinical or radiologic suspicion of intracranial aneurysms were studied prospectively with CT angiography and conventional angiography. The images were obtained and interpreted in a double-blind fashion by different radiologists. Conventional angiography, which was the reference standard in this study, diagnosed 17 aneurysms in 15 patients. The usefulness of the two types of images for surgical planning was evaluated by two neurosurgeons.
Results: No aneurysms were detected with either technique in eight patients. Both techniques showed 15 aneurysms in 14 patients. The maximum dimensions were less than 3.0 mm in three cases, 3.0-5.0 mm in four cases, and greater than 5.0 mm in eight cases. With conventional angiography used as the reference standard, CT angiography has one false-positive and two false-negative findings, resulting in a sensitivity of 88% (15/17) and a specificity of 89% (8/9). For 12 of 15 aneurysms, CT angiography was rated equal or superior to conventional angiography in depicting all aspects (shape, orientation, neck, and parent vessel) of the aneurysms.
Conclusion: We were able to detect aneurysms of the circle of Willis as small as 2 mm in size. Using conventional angiography as the reference standard, CT angiography has a sensitivity of 88% and a specificity of 89% for the detection of aneurysms in the circle of Willis. In almost all cases, CT angiography was equal or superior to conventional angiography in characterizing the aneurysms for surgical planning.