*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.
*'''Range and timing''', depending depends on main suspicions:
{|class="wikitable"
| '''Targets''' || '''Range''' || '''Bolus tracking delay'''<br>(ROI in aortic arch)