MR Mismatch Is Useful for Patient Selection for Thrombolysis

Geoffrey A. Donnan MD, FRACP Stephen M. Davis MD, FRACP Section Editors: The MR perfusion diffusion (PI/DWI) mismatch concept for the selection of patients for intravenous thrombolysis (IVT) was introduced with several smaller case series in the late 1990s and early 2000s,1 followed by larger series by many international groups over the last 8 years. A potentially salvageable penumbra was operationally defined as a PI/DWI-(volume) mismatch where PI indicates the hypoperfused tissue and DWI shows the more or less severe ischemic core.2 A mismatch volume of 20% (PI>DWI) has been widely accepted as indicator of a penumbral MRI setting. In an ideal world perfusion postprocessing would provide absolute values for cerebral blood flow (CBF). Perfusion maps could then indicate penumbra based on different thresholds for gray and white matter and thus …