Positron emission tomography is an imaging technique used to diagnose and monitor cancerous conditions. Commonly known as a PET scan, this test assists physicians in examining changes in specific bodily functions, which often suggest the presence of cancer or other illnesses before visible changes become apparent in a person’s anatomy.

PET scans are performed using a scanning device that looks like a doughnut with a large hole in the middle of it. As part of the procedure, a form of radioactive sugar is injected into the patient. The cells of the body absorb this sugar, which releases atomic particles called positrons. These positrons combine with electrons in the body to produce gamma rays. As gamma rays leave the body, they are detected by a special camera.

The images that result contain varying colors or levels of brightness that help physicians identify abnormalities that might indicate the presence of cancer. Cancerous tissues absorb more sugar than healthy tissues and therefore appear brighter in PET scan images.

PET scans also are sometimes used to diagnose or monitor other abnormalities, including those of the heart and brain.

PET scans are safe procedures that do not pose significant risks for most patients. The radioactive materials used are minimal and only remain in the body from a few hours to a few days. However, pregnant and breastfeeding women usually are urged not to undergo a PET scan because of the potential for exposing a fetus or newborn to potentially harmful radiation.

A radiologist or other nuclear medicine expert examines the images from a PET scan and sends a report to the patient’s physician. Results usually are available within a few days of the scan. Depending on the results of this test, additional tests or treatment may be recommended. For patients who have cancer, treatment methods may include chemotherapy, radiation therapy, surgery or other therapies.