<human>:  How does a Positron emission tomography (PET) scan work?
<bot>: A PET scan is a nuclear medicine imaging technique. It uses radioactive tracers to image the body. The tracer is injected into the patient's bloodstream and travels to the organs and tissues of interest. The tracer emits radiation that is detected by the PET scanner. The PET scanner produces images of the tracer's distribution in the body. The images can be used to diagnose and stage many diseases.