*Contraindications to intravenous contrast, since it can visualize cerebral vessels without it.
===ConstructionsSettings===*Preceding '''non-contrast CT''' of the head. If this has been done recently, generally repeat if a few hours has passed in an emergent setting.*'''Slice thickness''': Aneurysms are more readily visualized by thick slices such as 15mm, but thin slices such as 1.2 mm still need to be observed if there may be a focal occlusion or stenosis.
==Basic screening==