CT is computed tomography. The precautions to be taken before the examination vary depending on the part of the body to be examined. For example, metal objects should not be worn in the examination area, deep inhalation is required for lung examination, and fasting for more than 6 hours is required for abdominal examination. 1. Before the examination, metal objects such as belts, necklaces, rings, and metal accessories on underwear should not be worn in the examination area to prevent metal artifacts from appearing in the examination of the area, which may affect the results of film reading. 2. Lung computed tomography requires deep breathing. 3. Abdominal CT scanning requires fasting for at least 6 hours before the examination to avoid gastrointestinal contents affecting the results. 4. Head and bone and joint computed tomography scanning, need to keep the posture fixed. 5. Enhanced computed tomography, because of the possibility of allergic reactions to contrast media, you need to inform the doctor in advance of a history of allergy to contrast media, and then undergo an allergy test and sign an informed consent form. Some special computed tomography examinations, there are some special requirements, should follow the guidance of clinicians and imaging physicians, follow the doctor’s instructions.