The vascularization of the brain is relatively sophisticated, and the arterial system is commonly divided into the anterior and posterior circulatory systems. The anterior circulatory system originates from the internal carotid artery, which divides into the middle cerebral artery and the deep perforating branches of the middle cerebral artery, and further on the anterior cerebral artery, which is connected to the middle cerebral artery by the anterior communicating artery. The posterior circulation will have two vertebral arteries in the cervical region to form a basilar artery to supply blood circulation to the back of the brain. After the basilar artery goes upward, it divides into two posterior cerebral arteries, and there is a connection between the posterior cerebral arteries and the middle cerebral arteries by the posterior communicating arteries, which forms a complete Willis’ ring, and so the blood vessels of the brain have stronger compensatory function.