Non－contrast CT scan still plays a major role in the diagnosis of ischemic stroke,
differentiation from hemorrhagic stroke, and determination of therapeutic plans.
However, recently introduced perfusion CT and CT angiography using multi－slice
CT are now widely used in the clinical field. They provide information about the local
hemodynamic status and the exact location of occlusion in the same way as perfusion
MRI and MR angiography. Diffusion－weighted MRI describes the status of molecular diffusion of the brain tissue and detects cytotoxic edema, which enables diagnosis of acute stroke in a more sensitive way than CT or conventional T2－ weighted MRI. Perfusion MRI using gadolinium contrast is more sensitive and can detect hyperacute stroke even at the time of occlusion. A proper combination of PWI and DWI can evaluate the brain tissue at risk, e.g. ischemic penumbra, by detection of DWI/PWI mismatching areas and enables the timely diagnosis and treatment of acute stroke. MR angiography also provides an anatomic detail of stenosis or occlusion of cerebral vessels by the non－contrast TOF or contrastenhanced technique. Understanding the principles and pitfalls of new imaging modalities is very important in the evaluation of acute stroke, and proper communication with neuroradiologists is mandatory.
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