PURPOSE: Perfusion MR imaging is a new technique for the assessment of acute ischemic stroke. The aim of thisstudy was to evaluate the usefulness of this imaging in hyperacute ischemic stroke in comparison with conventionalCT and MR imaging. MATERIALS AND METHODS: Eight patients presenting the symptoms of acute ischemic stroke due tomiddle cerebral artery occlusion were included in this study. Within 2 hours of initial CT scan and 6 hours afterthe onset of stroke, perfusion MR imaging was performed in all patients using a single-section dynamiccontrast-enhanced T2*-weighted imager in conjunction with conventional routine MR imaging and MR angiography.Cerebral blood volume (CBV) maps were then obtained from dynamic MR imaging data by using numerical integrationtechniques. The findings of CBV maps were compared with those of initial and follow-up CT or MR images. RESULTS: The findings of CBV maps were obviously abnormal in all patients, as compared with normal or focal subtle abnormalfindings seen on initial CT and MR images. CBV in the occluded arterial territory was lower in all eight patients;two had focal regions of increased CBV within the affected territory, indicating reperfusion hyperemia. In allpatients, regions of abnormal CBV were eventually converted to infarctions on follow-up images. CONCLUSION: Perfusion MR imaging was useful for the evaluation of hemodynamic change occurring during cerebral perfusion inhyperacute ischemic stroke, and prediction of the final extent of infarction. These results suggest that perfusionMR imaging can play an important role in the diagnosis and management of hyperacute ischemic stroke.