===Choice of modality===
*'''[[CT of the head in stroke]]''' is generally the first investigation because of high availability.<ref name=Radiologyassistant-stroke>{{cite web|url=http://www.radiologyassistant.nl/en/p483910a4b6f14/brain-ischemia-imaging-in-acute-stroke.html|title=Brain Ischemia - Imaging in Acute Stroke|website=Radiology Assistant|author=Majda Thurnher}} Published: June 2008</ref> It detects about 60% of infarcts in the first 3 to 6 hours, and almost always thereafter.<ref name=Radiologyassistant-stroke/>
*'''[[MRI of the head in stroke]]''' is generally less available, but preferred if your clinic has established procedures for its performance in acute stroke., and there are no MRI contraindications
===How soon===