When a patient has a brain infarction, it can be detected with a brain CT. However, due to the different time of onset, the images shown by brain CT have some differences. After the symptoms appear in the acute stage of brain infarction, if thrombolysis or clot retrieval is needed, patients need to have CT examination immediately. Through CT examination, it is possible to determine whether there is bleeding. If there is no cerebral hemorrhage, it usually indicates that the patient may have an acute cerebral infarction. no image is shown above CT within 24 hours, but it can show special signs, such as signs of vasculitis, vascular obstruction or edema. The presence of a cerebral infarction can usually be determined if CT shows hypointense foci and edema foci more than 24 hours after the onset of the infarction. Because the images of cerebral infarction and cerebral hemorrhage are completely different, cerebral hemorrhage is a phenomenon of increased high-density signal, while cerebral infarction is a low-density signal, and by determining the difference in signal, you can determine whether it is a cerebral infarction or cerebral hemorrhage. In the late stage of cerebral infarction or recovery period, the foci and lesions of cerebral infarction can be judged by CT. At this time, local softening foci are often formed, showing cyst-like cavities or softening low-density changes, which are slightly different from low-density changes in the acute stage, mainly showing cavity performance with cerebral sulcus gyrus or with liquefaction and absorption after softening. In summary, regardless of the stage of cerebral infarction, it can be judged by CT.