Correlation of computed tomographic, angiographic, and neuropathological changes in giant cerebral aneurysms.

Giant aneurysms involving or adjacent to the circle of Willis exhibit three CT patterns: nonthrombotic, partially thrombotic, and completely thrombotic. Partially thrombotic aneurysms have the most specific pattern, consisting of a "target" configuration on the post-contrast scan. Ring calcification of the wall or mural thrombus is frequently observed in partially or completely thrombotic aneurysms. Calcification is not seen in nonthrombotic lesions. Angiographic and neuropathological findings are correlated with the CT findings.