Diffusion-and Perfusion-weighted Magnetic Resonance Imaging in Acute Ischemic Stroke

Diffusion (DWI)- and perfusion (PWI)-weighted magnetic resonance imaging are techniques which, due to their high sensitivity and specificity, allow the prompt diagnosis of acute ischemic stroke shortly after its onset. An increasing number of studies have demonstrated the practical application of DWI and PWI technology. Most of these studies, however, are non-randomized and are performed on small populations. Additionally, there is no standardization in both performing the exam and interpreting the results. This makes it difficult to create clear recommendations for using DWI and PWI in acute stroke. It is still hard to assess whether the information derived from these imaging tests may have predictive value; it is currently not possible to determine if DWI and PWI MR imaging allows more precise selection for thrombolytic therapy or enhances the results of it. We describe here briefly the technique of the DWI/PWI method and review the literature concerning the application of DWI/PWI technology in the diagnosis of acute cerebral ischemia. We outline the methods of DWI and PWI imaging, describe DWI/PWI mismatch, show results of current studies of DWI/PWI-guided thrombolysis, and evaluate the ability of DWI/PWI to predict patient outcome after acute stroke. Finally, on the base of current literature, we compare the diagnostic accuracy of DWI/PWI with other novel imaging techniques. We point out the crucial clinical issues which still need to be solved. (author)