The presence of shadows in the brain represents the presence of some lesions in the patient’s brain, which must be identified according to the density of the shadows.1. For example, if the shadows of the patient’s brain show high density, which is a brighter, white image on CT, consider brain hemorrhage. If the density of the shadow is low, that is, black, the most common cases in this case are cerebral infarction or softening foci in the brain, and brain cysts, etc. Tumors of lower grade will also show low density shadow on CT, while glioblastoma, germ cell tumor, lymphoma and other tumors show high density shadow. 2. When the patient finds this kind of shadow in the CT of the head, if the nature cannot be determined, the nature can be clarified by imaging. If the nature of the tumor cannot be determined, the nature can be clarified through imaging or higher level examination, such as MRI.