PET-CT is a common examination method in nuclear medicine, which not only has the function and imaging characteristics of PET, but also incorporates the anatomical image characteristics of CT, which is an organic combination of the two, so it is mainly used to examine the following aspects: 1. tumor diagnosis: also PET-CT is the most widely used, PET-CT imaging can check some relatively small tumor lesions at an early stage, and it can identify the benign and malignant nature of tumors, and it can accurately analyze the tumor lesions already found. PET-CT imaging can detect small tumor foci at an early stage, and can identify the benign and malignant nature of tumors, and can accurately analyze tumors that have already been detected, as well as monitor the residual foci of tumors or identify recurrent foci, necrosis, surgical scars, edema and other lesions. 2. Identification of myocardium: PET-CT can be used to differentially diagnose ischemic, but surviving myocardium and infarcted myocardium.