There are two general situations in which injections are needed for CT: 1) infants and young children need to be kept still for CT examinations, and infants and young children are prone to be uncooperative with the examination, so the doctor will suggest that infants and young children should be given a Valium injection to help them complete the examination; 2) CT enhancement examinations or vascular examinations need to be injected with a contrast agent, which is used to help in the diagnosis of lesions so as to determine the relationship between the nature of lesions and surrounding tissues, so injections are needed for CT in these two situations. The contrast agent is used to help diagnose the lesion and determine the relationship between the nature of the lesion and the surrounding tissues, so both of these cases require injections for CT.