The radiation of PETCT will disappear in about 1 day. The radiation of PETCT is mainly due to the injection of developer before the examination, and the commonly used developer is 18F-FDG, a glucose metabolite, which is mainly discharged through the kidneys and is not absorbed by the body, and the half-life of 18F-FDG injection must be between 105-115min, and the nuclides in the body will be reduced by half in about 2 hours, and it will be metabolized in about 1 day. PETCT examination after the patient, through a large amount of water, enhance urination, can accelerate the imaging agent out of the body, and 18F-FDG basically 10 half-life, the body’s nuclide basically eliminated clean. After PETCT examination specific precautions need to consult a professional doctor’s advice and suggestions. It is recommended that patients should consult a doctor in time if they feel unwell, and should not be negligent to avoid delays.