1, neurological lesions: craniocerebral trauma, cerebral infarction, brain tumor, inflammation, congenital malformation, etc. It is the routine and preferred examination method, which can clearly show cerebral contusion, acute intracerebral hematoma, epidural and subdural hematoma, craniofacial bone fracture, intracranial metal foreign body, etc. CT diagnoses acute cerebrovascular diseases such as hypertensive cerebral hemorrhage, subarachnoid hemorrhage, cerebral aneurysm and arteriovenous malformation rupture hemorrhage, cerebral infarction, etc. CT is less sensitive than MRI for acute cerebral infarction, especially for those within 6 hours of onset. 2.Thoracic lesions: It has a very satisfactory effect on showing pulmonary lesions, and has a high diagnostic value for pulmonary trauma, infectious lesions, tumors and other uniform. It is also satisfactory for the display of mediastinal masses, lymph nodes and pleural lesions, and can show the relationship between intrapulmonary masses and mediastinum. 3.Abdominal organs: For the substantive organs such as liver, gallbladder, spleen, pancreas, kidney and adrenal gland, the display is clear, and for tumors, infections and traumas, it can clearly show the exact part of the anatomy and the degree of lesions, and has a high value for lesion staging, etc. It is of great value for the diagnosis and differential diagnosis of intra-abdominal masses. 4.Pelvic organs: There is rich fat interval between pelvic organs, which can accurately show the invasion of tumor to adjacent tissues. Therefore, CT has become an important tool for diagnosis, clinical staging and radiotherapy design of ovarian, cervical and uterine, bladder, seminal vesicle, prostate and rectal tumors. 5.Bone and joint: (1) Small lesions in bone and muscle are often not shown by X-ray plain film covered by bone cortex. (2) Bones and joints with complex structure, such as spine and sternoclavicular joint. (3) X-ray suspicious lesions, such as small fractures of joint surfaces, soft tissue abscesses, bone cortical destruction caused by intramedullary bone tumors, and observation of tumor infiltration into soft tissues, etc. (4) Display of structures inside and around the bone destruction area: for example, dead bone, calcification, ossification in the destruction area, as well as bone growth, soft tissue abscess and swelling around the destruction area are significantly better than conventional X-ray plain films. (5) For articular cartilage, ligaments, meniscus, synovial membrane, etc., MRI examination is appropriate.