[en] It is important to see how quickly MRI is able to detect ischemic lesions and what kind of efficacy the Gd-DTPA enhanced MRI can show in cases of cerebral infarctions in their acute and subacute stages. CT and MRI were performed within the first 6 hours after the onset. Then, the serial CT and MRI were used to follow the case till the 3rd week after onset. T₂WI on MRI depicted the ischemic lesion by a high-signal-intensity area in all cases within the first 6 hours, while CT showed no ischemic lesions. The high-signal-intensity area along the Sylvian fissure indicates a further ischemic area which spread into the white matter of the MCA territory in the 24 hours after ischemic insult. In the second week after onset, in some cases MRI failed to show the ischemic lesions by the phenomenon called 'the fogging effect'. During this period, only Gd-DTPA enhanced MRI demonstrated the ischemic lesion by contrast enhancement on T₁WI. We experienced two such cases among 12 cerebral infarctions; both lesions were located in the basal ganglia. At times, the extent of an ischemic lesion can be detected more extensively on MRI than on CT. This finding indicates that the ability to detect the blood-brain barrier disruption is greater in MRI than in CT. (author)