The purpose of these guidelines is to assist physicians in recommending, performing, interpreting, and reporting the results of 18 F-FDG PET/CT for oncologic imaging of adult and pediatric patients. II. BACKGROUND INFORMATION AND DEFINITIONS PET is a tomographic scintigraphic technique in which a computer-generated image of local radioactive tracer distribution in tissues is produced through the detection of annihilation photons that are emitted when radionuclides introduced into the body decay and release positrons. 18F-FDG PET is a tomographic imaging technique that uses a radiolabeled analog of glucose, 18F-FDG, to image relative glucose use rates in various tissues. Because glucose use is increased in many malignancies, 18F-FDG PET is a sensitive method for detecting, staging, and monitoring the