Enhanced CT is generally not needed for tumor screening unless there are special circumstances. In general tumor screening examination, ordinary CT, tumor markers and ultrasound are basically carried out without the need for enhanced CT, etc. Only when the CT scanning display is not clear or the situation is not clear, the patient will be allowed to undergo further enhanced CT, so as to carry out a better analysis and judgment of the lesion site. Enhanced CT is to determine the nature and situation of the tumor according to the characteristics of the blood supply of the lesion by intravenous injection of contrast agent or contrast agent, but it can not be used as the final means of diagnosis of the tumor, and it needs to be further improved by biopsy of pathological tissues.