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PET Scans

Reviewed by: Emily F. Conant, MD

Updated October 1, 2010

Positron Emission Tomography, also known as a PET scan, is used to detect cancer throughout the body. It takes pictures of cells in the body. Usually, doctors order PET scans after a cancer diagnosis to see if the cancer may have traveled outside the breast to the lymph nodes or other major organs, like the bones, liver, lungs or brain. It also is useful for checking whether treatment for metastatic breast cancer is working.

Before the test, your doctor will inject a substance made up of sugar and radioactive material. This material will be attracted to cells with high levels of activity, which is common near cancer cells. On the PET scan, areas of activity show up brighter than other areas. After the scan, your doctor may order more tests to get detailed information about any suspicious areas.

Getting the Test

Your doctor may ask you not to eat for several hours before the test. If you have diabetes or you other illnesses, you’ll receive special instructions. You must remove metal jewelry and other objects before the test, and you may be asked to change into a hospital gown.

A PET scan machine looks somewhat like a CAT (CT) scan machine or an MRI (Magnetic Resonance Imaging) machine. After the injection, you will lie down or sit quietly for about an hour while your body absorbs the sugar-radioactive mixture. Then, you will lie on a narrow table that will move through a hole in the center of a round scanner. This scanner will take pictures of your body using x-rays. You must lie very still. The test lasts about 30 minutes. Except for the needle prick from the injection, you should not feel pain during the test.