A cardiac Positron Emission Tomography (P.E.T.) scan is a type of stress test in which blood flow to the heart muscle is seen with a radiotracer and a special scanner. P.E.T. provides an accurate non-invasive assessment of the heart arteries. Pictures of the heart blood flow are taken before and after pharmacologic stress instead of exercise to determine if maximum blood flow is restricted by narrowing of the arteries. Now, P.E.T. scan diagnoses heart disease non-invasively with 96-98% accuracy in individuals with or without symptoms of heart disease, allowing treatment even before symptoms appear.