The full name of PET examination in Chinese is Positron Emission Computed Tomography, which means that positron nuclide is used to label the substrate required for human tissue metabolism, or its analogues as radiopharmaceuticals. After being introduced into the body intravenously, it is taken up and used by tissue cells to participate in the metabolism of substances such as sugar, protein, fat or nucleic acid in the human body, thus reflecting information and changes in tissue metabolism, and also allowing accurate localization for clinical application. It has an important role in early diagnosis, efficacy evaluation and etiological exploration of diseases.