A breast positron emission tomography (PET) scan is an imaging test that uses a radioactive substance (called a tracer) to look for breast cancer. This tracer can help identify areas of cancer that an MRI or CT scan may miss.

See also: PET scan

A PET scan is most often used when other tests, such as MRI scan or CT scan, do not provide enough information.

A breast PET scan is used only after a woman has been diagnosed with breast cancer. It is done to see if the cancer has spread to other parts of the body such as lymph nodes, liver, lung or bones.

If you have breast cancer, your doctor may order this scan:

• Soon after your diagnosis to see if the cancer has spread
• After treatment if there is concern that the cancer has come back
• During treatment to see if the cancer is responding to treatment

A PET scan is not used to screen for, or diagnose, breast cancer.

The health care provider will inject a small amount of a radioactive material into one of your veins, usually on the inside of the elbow. The substance travels through the blood. It is more likely to collect in cancer tissue.

You will be asked to wait nearby as the radioactive substance is absorbed by your body. This usually takes about 1 hour.

Then, you will lie down on a table that slides into a tunnel-shaped hole in the center of the PET scanner.

The PET machine detects energy given off by the radioactive substance and changes it into pictures. The images are sent to a computer, where they are displayed on a monitor for the health care provider to see.

You must lie still during the PET scan so that the machine can produce clear images of your lungs.

Most PET scans are now performed along with a CT scan. This combination scan is called a PET/CT.

The test takes about 90 minutes.

You must sign a consent form before having this test. You will be told not to eat anything for 4 - 6 hours before the PET scan, although you will be able to drink water.

Tell your doctor if you are pregnant or think you might be pregnant.

Also tell your doctor about any prescription and over-the-counter medicines that you are taking, because they may interfere with the test.

Be sure to mention if you have any allergies, or if you’ve had any recent imaging studies using injected dye (contrast).

People with diabetes who take insulin injections will need special preparation. Call the PET scan office the day before the study for instructions.

During the test, you may need to wear a hospital gown. Take off any jewelry, dentures, and other metal objects because they could affect the scan results.

You will feel a sharp prick when the needle with the radioactive substance is inserted into your vein. You shouldn’t feel anything during the actual PET scan.