Shadow in CT brain: 1. It can be seen in cerebral infarction, which appears as hypointense shadow on CT, and irregular hypointense shadow in patches in acute stage. 2. Shadow in CT brain can be seen in intracranial occupational disease, which can be seen in primary occupational tumor or metastasis, and patients have headache and nausea. 3. Shadow in CT brain may be partial artifact, especially in the head. When wearing metal ornaments, there will be artifacts when doing head CT, and more artifacts in brainstem and medulla oblongata. If the cause of the artifact is not determined by CT brain, the patient may be given further CT enhancement, MRI scan or MRI enhancement to determine the nature of the disease. Treatment should be tailored to the cause, such as symptomatic treatment of cerebrovascular disease or occupational disease.