PET-CT is now a popular cancer screening test, and many people regard it as an important way to detect cancer. Why is PET-CT the most advanced cancer screening test? PET-CT is a fusion of PET (functional metabolic imaging) and CT (anatomical structure imaging), which are already quite mature technologies, and realizes the same-machine fusion of PET and CT images. The advantages of the two most high-grade imaging technologies, PET functional imaging and spiral CT fine structure imaging, are merged into one, forming complementary advantages. One imaging can obtain PET images and CT images of the corresponding parts, which can accurately characterize the lesion and accurately locate the lesion, and its diagnostic performance and clinical utility value are higher. Most of the tumors in the body have vigorous metabolism, malignant tumors have more vigorous metabolism than benign tumors, and the higher the degree of malignancy, the higher the metabolic level. According to this characteristic, before doing the examination, the examinee is injected with a certain amount of metabolic substances – positron tracer, and under PET-CT, using PET tracer detection technology, the doctor can accurately see the distribution of metabolic substances, and if there are more metabolic substances gathered in any place, it means that the metabolism here is vigorous, and according to the degree of gathering and the CT performance of the metabolic substances, the metabolism will be more vigorous. According to the degree of metabolic substances aggregation and CT performance, it can determine whether there is a tumor and whether the tumor is benign or malignant. Therefore, PET-CT examination is the most suitable examination for cancer prevention at present, and it has advantages that other examinations cannot have. Those who have the conditions for medical checkups can consider having a medical checkup once a year.