What Is PET Scan?

A PET scan (positron emission tomography) is an imaging test that can help reveal the metabolic or biochemical function of the tissues and organs. It uses a radioactive drug (tracer) injected into a vein to show normal and abnormal metabolic activity. It can often detect the abnormal metabolism of the tracer in diseases before the disease shows up on other imaging tests. 

It collects in specific tissues of the body. Generally, the more active the tissue, the more tracer it collects and will give off more radiation.