Precautions for 18F-FDG PET/CT tumor imaging 1. Patients should not remain lying down during the entire acquisition period (15-45 min), patients with a history of claustrophobia, patients who cannot raise their arms up, and patients with a history of glucose allergy should not undergo this test. 2. Patient preparation prior to arrival The patient is instructed to fast for 4-6 hours prior to 18F-FDG injection and not to drink beverages (except water) for the purpose of reducing physiologic blood glucose levels and reducing serum insulin concentrations to near basal levels. Drinking water is encouraged, but any intravenous solution containing glucose or parenteral administration should be discontinued for 4-6 hours. 3.Preparation before injection a. For brain imaging, 18F-FDG injection and post-injection uptake, the patient should rest in a quiet and light-proof environment. b. For whole body imaging, 18F-FDG injection and post-injection uptake, the patient should be in sitting or lying position to avoid muscle uptake. c. Measure blood glucose level before 18F-FDG injection. If the blood glucose level exceeds 150-200 mg/dl, the patient should be injected with insulin to reduce the blood glucose level, but the injection of 18F-FDG should be delayed until a certain time after the insulin injection (the delay depends on the type of insulin injected and the route of insulin administration).