Positron emission tomography, also called PET imaging or a PET scan, is a diagnostic examination that involves the acquisition of physiologic images based on the detection of radiation from the emission of positrons. Positrons are tiny particles emitted from a radioactive substance administered to the patient, where they localize in appropriate areas of the body and are detected by the PET scanner. The subsequent images of the human body are used to evaluate a variety of diseases.

PET scans are used most often to detect cancer and to examine the effects of cancer therapy. These whole body scans currently rely on the greater uptake of the sugar in rapidly growing tumors, as compared to normal surrounding tissues. For certain cancers, including lung, colon, melanoma and lymphoma, PET scanning offers the most accurate test available at this time.

PET scans of the heart can be used to determine blood flow to the heart muscle and help evaluate signs of coronary artery disease. PET scans of the heart can also be used to determine if areas of the heart that show decreased function are alive rather than scarred as a result of a prior heart attack, called a myocardial infarction. Combined with a myocardial perfusion study, PET scans allow differentiation of nonfunctioning heart muscle from heart muscle that would benefit from a procedure, such as angioplasty or coronary artery bypass surgery, which would reestablish adequate blood flow and improve heart function.

PET scans of the brain are used to evaluate patients who have memory disorders of an undetermined cause, suspected or proven brain tumors or seizure disorders that are not responsive to medical therapy and are therefore candidates for surgery.