The cranial ultrasound, which refers to transcranial Doppler examination, is not able to see brain injury. Because transcranial Doppler mainly assesses the blood flow velocity of cerebral blood vessels and the presence of vascular stenosis, it cannot see the brain parenchyma and whether there is bleeding in the cerebral blood vessels. Therefore, when a patient suffers from cranial trauma or acute neurological deficits, a CT or MRI of the head must be done to clarify the symptoms. If the patient has head trauma, head CT is the fastest and most direct test to see if there is brain damage, and the head CT can observe whether the patient has subarachnoid hemorrhage, brain parenchymal hemorrhage, and brain contusion. In the case of primary, for example, cerebral infarction or primary cerebral hemorrhage or hypertensive cerebral hemorrhage, head CT or head MRI brain function weighted imaging is required to observe the changes in the patient’s condition.