A brain imaging system includes a first imaging device, a second imaging device, a third imaging device and a central processor. The first imaging device captures a first brain image, and calculates a cerebral blood flow, a cerebral blood volume, a cerebral blood mean transit time and a first contrast agent time to peak. The second imaging device captures a second brain image, and calculates the cerebral blood flow, the cerebral blood volume, the cerebral blood mean transit time and a second contrast agent time to peak. The central processor generates an image of a vessel occlusion, infarction or ischemia region respectively according to the vessel occlusion, infarction or ischemia regions in the first brain image and in the second brain image. The third imaging device obtains a brain atrophy region according to the cerebral cortex volume calculated by the third imaging device.
