CT is a new examination method which is convenient, rapid, safe, painless, non-invasive and non-hazardous, with clear images, high density resolution, clear anatomical relationships and clear lesion visualization, which greatly improves the diagnosis of intracranial lesions (such as occupying lesions, vascular lesions, cerebral piperine, etc.) and can determine the pathological nature of lesions. It has become a very important auxiliary diagnosis and is popular among medical practitioners and patients. The relationship between CT value and lesion The density of CT image is expressed by CT value. The CT value of the same tissue varies depending on the scanning conditions and the density of adjacent tissues. On CT images, the brain parenchyma is denser, and the ventricles, brain pools and sulci show their respective size, shape and location because they are filled with cerebrospinal fluid and appear as low-density areas. If the sulcus is widened and the ventricles are enlarged, the lesion may be considered to be a brain pallidus; deformation or displacement of the ventricular shadow may be considered to be an occupational lesion. Density is related to the nature of the lesion. If the lesion is above the brain parenchyma, it is a high-density lesion, including calcification, hemorrhage, hematoma and high-density tumor; if it is below the brain parenchyma, it is a low-density lesion, including infarction. Cysts, edema, and low-density tumors are considered. After intravenous injection of contrast agent, the density of certain lesions can be increased (i.e., enhanced or strengthened), which often occurs in lesions with rich blood circulation and brain tissue with disrupted blood-brain barrier, when the image is clearer. Therefore, in terms of clinical diagnosis, CT value is a quantitative indicator of the body reflecting the density of normal and diseased tissues. Taking the density of normal brain tissue as the standard, the density of abnormal images can be divided into the following categories: 1. High-density shadow: the density of the lesion is higher than the density of normal brain tissue is called high-density shadow, which is white. It is common in calcification, hemorrhage, solid masses, etc. 2, low-density shadow: the density of the lesion is lower than the density of normal brain tissue is called low-density shadow, black palladium, common in cerebral hard infarction, edema, fat, liquefaction, necrosis, etc. 3.Isointensity shadow: The density of the lesion is the same or similar to the density of normal tissue. Commonly seen in hematoma absorption stage, tumor, etc. 4.Mixed density: the coexistence of high and low density lesions in the lesion is called mixed density shadow. It is common in malignant tumors, cerebral hemorrhage absorption process, etc. In the diagnosis of epilepsy, CT and EEG are two important tools. CT focuses on anatomical pathology and can help determine the nature of the pathology; EEG focuses on physiological anatomy and can provide the type of epilepsy and the location of lesions. The combination of the two can play a crucial role in the diagnosis of epilepsy. The lesions found in CT images of patients with epilepsy are also quite complex. According to the literature, the main CT manifestations are cerebral vulgaris, brain tumors, cerebrovascular malformations, cerebral infarction, traffic hydrocephalus, medial temporal lobe herniation, corpus callosum malformation, cerebral softening, calcified foci and other unexplained high or low density changes. CT, as an important modern examination tool for neurological diseases, has many advantages in addition to the visualization and accurate examination of structural lesions of the brain. CT can only detect most of the structural lesions but cannot confirm the causes other than structural lesions. Therefore, the combination of CT and EEG is necessary to improve the accuracy of clinical diagnosis.