Generally CT can be examined for all organic diseases, especially for the qualitative diagnosis of organic and occupying lesions with large density differences. For example, diseases of the brain, in which the examination of tumors, hemorrhage, infarction and other lesions is effective. Diseases of the chest can be examined well because the lungs contain air, whether it is inflammation or tumor, and the contrast between the air-containing lung tissue is particularly obvious. Diagnosis of mediastinal diseases, peripheral large vessels, and lesions other than fat can also be made. For abdominal parenchymal organs, such as tumors and stones in the liver, gallbladder, pancreas, spleen and kidney, a clear diagnosis can be made. However, CT is poor for the uterus or prostate, but the disease can be predicted from changes in gross morphology and further examination can be done.CT is poor for the diagnosis of diffuse lesions, especially for neurodegenerative diseases. For gastrointestinal lesions, due to the emptiness of the gastrointestinal tract and the thin wall of the stomach, the display effect is not as good as that of gastroscopy, but CT can be used to understand the extent of tumor invasion and whether there is any distant metastasis. In conclusion, CT has a better examination effect, and CT has a better examination effect on lesions of large blood vessels, such as coronary arteries, aorta, and blood vessels of the lower limbs, through enhanced scanning and three-dimensional reconstruction, which can show a performance similar to that of angiography.