MRI uses magnetic field to examine the body, so there is no radiation to the body, and it can scan the organs in multiple directions and parameters, which is good for finding lesions and identifying the nature of lesions, especially the resolution of soft tissue is higher than CT and other examinations. CT examination is easier, more convenient and less expensive, and is better than other examinations for hemorrhagic lesions in the lungs and head, as well as for whole-body scanning, which is preferred for the examination of critically ill patients. The disadvantage is that there is a small amount of radiation to the body, the resolution of soft tissue is poor, and the diagnosis rate of early cerebral infarction is also low.