The vast majority of tumors with increased uptake of 18F-FDG show up on PET but 18F-FDGPET has limited diagnostic value in certain tumors such as thyroid p renal cell carcinoma. Well-differentiated tumors p tumors with fewer tumor cells and mucin-producing tumors such as bronchoalveolar carcinoma and intraductal papillary mucinous carcinoma take up less 18F-FDG. Renal and bladder tumors are also difficult to detect with 18F-FDGPET because 18F-FDG is excreted from the urine. 18F-FDGPET is valuable in diagnosing tumors, but lacks tumor specificity, and a variety of normal organs also have increased uptake of 18F-FDG. Brain tissue p myocardium p tonsils p salivary glands p reactive hyperplastic lymph nodes p liver p gastrointestinal tract p testes and muscle have increased 18F-FDG uptake. The rate of 18F-FDG uptake is also increased in non-neoplastic lesions. Benign head and neck tumors p intestinal adenomas p inflammatory tissues can have high uptake rates similar to those of malignant tumors. 18F-FDGPET can reveal lesions that are not detected by conventional imaging, thus changing the stage of the disease. Lymphoma is a disease that involves multiple lymph nodes throughout the body, and detection of the involved lymphatic tissue and other organs is a prerequisite for proper staging. staging increased and treatment options changed in 60% of patients. In a prospective study [3] that included 88 patients with Hodgkin’s lymphoma, 18F-FDGPET resulted in a change in staging in 20% of patients and a change in treatment plan in 18% of patients compared with conventional staging methods. PET/CT can be used as a complement to staging patients with cervical cancer FIGO stage IB or higher.Loft et al [4] divided 120 patients with cervical cancer into two groups: one group underwent radical hysterectomy, including lymph node dissection; the other group underwent chemoradiotherapy. In comparison with the results of pathology and/or follow-up, 27 patients who underwent radical hysterectomy after PET/CT showed no pelvic lymph node involvement in 23 cases, 22 of which were true negatives and 1 false negative, and the other 4 cases showed positive PET/CT, 3 of which were true positives and 1 false positive. Positive predictive value was 75%, negative predictive value was 96%, sensitivity was 75%, and specificity was 96%. PET has a good role in the restaging of non-small cell lung cancer p breast cancer p esophageal cancer p colorectal cancer p head and neck tumors p lymphoma p melanoma p sarcoma and other tumors, with a sensitivity of 80-95%, specificity of 75-90%, and accuracy of 80-90%. three examination methods, CTp ultrasound endoscopic fine needle aspiration and PET/CT, in the restaging of esophageal cancer after neoadjuvant treatment with chemoradiotherapy, had a correct rate of differentiating T4 The correct rates of differentiation between T4 and T1-3 were 76%, 80% and 80%, respectively; the correct rates of lymph node determination were 78%, 78% and 93%, respectively; and the correct rates of complete remission determination were 71%, 67% and 89%, respectively. G-CSF and EPO can increase 18F-FDG uptake in the bone marrow p spleen [5], making the evaluation of lesions in these areas difficult, and the uptake values usually return to baseline levels after 3 weeks of drug withdrawal. The bone marrow recovery period after chemotherapy suppression also increases 18F-FDG uptake.