CT examinations are more radioactive, tens or hundreds of times more than chest films or ordinary plain films. MRI is mainly used for cerebrovascular diseases, including cerebral hemorrhage and cerebral infarction; it can also be used to examine the condition of intracranial blood vessels, including whether there is blood vessel stenosis and the degree of stenosis, whether there is aneurysm or arteriovenous malformation, mainly for examining the lesions of large intracranial blood vessels; it is also used to examine lumbar disc herniation and cervical disc herniation; it can also be used to examine liver diseases; in addition, it can also be used to examine cranial trauma. CT examinations include CT of the chest, CT of the upper abdomen, CT of the lower abdomen, CT of the head, etc., and also CT of the cervical disc or CT of the lumbar disc, etc.