Ninety percent of PET-CT clinical applications are for tumor diagnosis, differential diagnosis, or guiding clinical puncture biopsy, or giving tumor for corresponding clinical staging, or searching for tumor primary series clinical applications. So nowadays, many lesions that are difficult to be diagnosed by conventional examination methods, ultrasound, CT or MRI, mostly rely on PET-CT for examination. And PET-CT can provide very effective meaning and value for the differential diagnosis of tumor. Nowadays, 18F-FDG imaging agent is routinely used. Even a series of imaging agents with carbon-11-labeled choline (11C-CHO) or methionine (11C-MET) can be used to diagnose and differentially diagnose tumors for different tumors to achieve a very good diagnosis of tumors.