1.Patients with confirmed malignant tumor: PET-CT accurately stages the lesion, clarifies whether there are metastases in other organs, helps to choose the treatment plan and avoid inappropriate surgery and treatment. 2.During and after malignant tumor treatment: evaluate the treatment effect, monitor the recurrence and metastasis after tumor surgery and radiotherapy, and distinguish tumor from scar tissue. 3.Discovering metastatic lesions but unknown primary lesions: PET-CT can discover many primary lesions that cannot be found by other examinations. 4.Patients with suspected tumor: If tumor markers are increased and lesions are found by CT and MRI but the nature cannot be clarified, PET-CT can characterize many lesions. 5.Patients with family history of tumor: patients with certain chronic diseases, long-term smoking, alcoholism or mental stress. 6.Patients with epilepsy: PET-CT can detect the epileptogenic foci in the brain, locate them and then perform surgery or radiotherapy to cure epilepsy. 7.Patients with myocardial infarction or severe myocardial ischemia: PET-CT is the most reliable method to determine whether the myocardium at the site of myocardial infarction is alive or not, which is directly related to whether one can receive coronary artery grafting and intracoronary angioplasty, and to estimate the prognosis of surgery. 8. Health checkup for people over 40 years old.