Fig 6. Using imaging-derived physiologic information to guide therapy. The patient is a 38-year-old man who was found with a severe left hemiparesis. The precise time of stroke onset was unknown. The noncontrast CT scan was remarkable for a hyperattenuated focus in the region of the right MCA (not shown). A, CT angiography demonstrates occlusion of the right MCA (arrow), but with reconstitution of distal branches likely due to collateral circulation. B, Diffusion MR imaging shows abnormal diffusion in the distribution of the right lenticulostriate arteries, but with sparing of the remainder of the MCA territory, including the cerebral cortex. C, Perfusion MR imaging displays abnormalities involving the entire right MCA territory. The time-to-minimum-perfusion map at the same level as the DWI image demonstrates a perfusion deficit that is much larger than the DWI abnormality. Because of the large diffusion/perfusion mismatch and the likely poor long-term outcome in the absence of treatment in this man with a young family, the decision was made to proceed to intra-arterial thrombolysis. D, Right common carotid angiogram demonstrates a cutoff of the right MCA, corresponding to the previously obtained CTA (arrow). E, After manipulation with a microguidewire and infusion of urokinase, right MCA flow was established (arrow). F, A follow-up head CT scan shows infarction in the region of the right corona radiata and a small portion of cerebral cortex. The patient made an excellent recovery with minor neurologic deficits at discharge.