Positron emission tomography(PET) is a noninvasive, diagnostic nuclear imaging technique that produces threedimensional images of functional processes of the body. PET uses unique isotopes especially of carbon, nitrogen, oxygen, fluorine, that are radioactive in nature, to study the various functional processes that are difficult to demonstrate by any other method. The amount of radioactive material required is very small and hence does not harm the system. The precise type of radioactive material and its delivery method depends on which organ or tissue is being studied by the PET scan. The radioactive material may be injected into a vein, inhaled or swallowed. More radioactive material accumulates in areas that have higher levels of chemical activity. This often corresponds to areas of disease and shows up as brighter spots on the PET scan. The most commonly used tracer is 18-fluorine coupled with glucose which is the main source of energy for living tissues. Active tissues within the body like tumors, inflammation can be visualized as it takes up more glucose than other tissues i.e. the concentrations of tracer imaged will indicate tissue metabolic activity by virtue of the regional glucose uptake.