We have investigated the diffusion-weighted MR imaging (DWI) findings of 40 patients with acute occlusion of internal carotid artery or middle cerebral artery on admission. According to the extent of high intensity areas (HIAs), DWI findings were classified into 4 types, type 1: no detection of HIAs, type 2: detection of HIAs in perforator's territory, type 3: detection of HIAs of limited part of cerebral cortex, type 4: detection of extended HIAs. 4 patients of type 1 were examined within 2 hours after onset. The earliest case with HIA detected by DWI was examined 30 min. after onset. The detection of HIAs on DWI was correlated well to the CBF values obstained by 99m Tc-HMPAO SPECT. HIA was detected exclusive-ly in the hypoperfused area where CBF value was under 20 ml/100 g/min. All 16 patients of type 4 were received conservative therapy, because CBF value on HIAs was very low (0-14 ml/100 g/min.) as irreversible lesions. 14 of 24 patients of type 1-3 underwent revascularization therapy in acute phase and had good results. Some of type 1-3 patients had the indication of revascularization therapy. We concluded that DWI classificasion could be useful for selecting a candidate for revascularization therapy in acute phase.
