MRI is not more harmful than CT. MRI is not harmful in any way, its imaging by magnetic field and there is no radiation damage to the body. Even if CT examinations have some radiation, doing one CT will not bring great harm to the body because the radiation content of doing one CT is very low. In cerebrovascular department, both CT and head MRI are very important. For example, if a patient suddenly has symptoms of neurological deficits such as inflexible limb movement and numbness of limbs, the first time to improve the head CT, through which the head CT can clarify whether the patient has serious diseases such as cerebral hemorrhage. If there is no brain hemorrhage, the patient is considered to be caused by cerebral infarction disease, and the patient can be treated according to the acute stage of cerebral infarction at an ultra early stage. Head MRI is also very commonly used in clinical practice and shows lesions in the posterior cranial fossa and brainstem area more clearly. Especially in the acute stage of cerebral infarction, the head MRI can be visualized within two hours of the onset, so it can guide the treatment and has a very important role in determining the prognosis.