Diffusion and perfusion MR for acute ischemic stroke: Emergency clinical protocol and advances

The aim of this paper was to describe emergency MR protocol and to present advanced MR techniques for acute ischemic stroke under the clinical investigation. Diffusion-weighted imaging (DWI) can identify early ischemic change that is hard to detect on CT or T2-weighted imaging. Perfusion changes always precede the development of DWI changes. Perfusion lesion is larger than DWI lesion and the eventual infarct during the first 6–12 h. The penumbral tissue is considered to exist within the area of diffusion–perfusion mismatch (PWI > DWI area)—the area with normal diffusion but reduced perfusion. Diffusion–perfusion mismatch with vascular reserve that is tissue with maintenance of rCBV and moderate reduction of rCBF is a candidate for thrombolysis. In contrast, markedly decreased rCBV and rCBF is contraindication. FLAIR intraarterial signal is a useful sign that suggests evidence of DWI–PWI mismatch.