PET utilizes 'positron' emitting radiotracers to deliver images that provide an insight into the biochemical and physiological processes of the human body. The biochemistry and physiology of the body is altered when it is in a disease state. Since, altered function precedes structural changes, PET has the capability to permit an earlier diagnosis, giving also information better related to prognosis and therapy. Therefore, it is acquiring a primary role in diagnosing and evaluating many disease states, with main reference to cancer.