Head CT and head MRI have their own strengths in examination, as follows: 1. Head CT is radioactive and has radiation, while head MRI does not have radiation, but if the patient has metal items such as steel plates and stents, MRI cannot be performed. 2. Head CT is clearer than MRI for hemorrhagic diseases of the brain, while for ischemic diseases such as cerebral infarction, MRI is better than CT. Magnetic resonance can detect small lesions that cannot be detected by cranial CT, and it can also distinguish acute lesions from old lesions, which is better than CT. 3, cranial vascular examination, CT and magnetic resonance can be performed, but CT needs to add contrast agent, which is more expensive, but the clarity is clearer than magnetic resonance vascular examination. 4, cranial tumor diseases, whether CT or magnetic resonance, may not be visible during plain scanning. Early cerebrovascular disease may not be clearly seen in less than 24 hours of onset, and CT and MRI may need to be reviewed in the future when the onset is less than 24 hours. 6.