PET Scan

Author: OncoLink Team
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What is a PET scan?

A PET (positron emission tomography) scan is an imaging test. A PET scan can see how tissues and organs in your body are working and find disease or inflammation. 

How does a PET scan work?

PET uses a radioactive substance, called a tracer. The tracer can be given in a vein (IV), swallowed, or inhaled (as a gas) into the body. The radioactive tracer is often attached to glucose (a sugar molecule). The tracer and glucose combination is called FDG (fluorodeoxyglucose). 

After it enters your body, it goes to areas that have higher levels of chemical activity (such as areas where there is cancer or other disease). Tumor cells have a high rate of activity. This causes the tumors to take up, or attract, more of the tracer. This makes the cancer cells look more "active" or brighter than other areas on the scan pictures. 

Often, a CT scan is done at the same time. The machine merges the images from the PET and CT together to determine functional (PET) and structural information (CT). A PET/CT test helps diagnose cancer and gives more information, including whether a tumor is benign (non-cancerous) or malignant (cancerous), whether the cancer cells are active or dead, and how well the cancer is responding to treatment. 

It is important to remember that a PET scan can show many things. The scans can’t tell the difference between activity due to a tumor and activity due to non-cancerous processes, such as inflammation or infection. 

PET Scan for Breast Cancer

When used to detect breast cancer, a tracer called fluoroestradiol F18 may be used. This tracer can detect estrogen receptor (ER)-positive tumors. It can be used to find recurrent or metastatic breast cancer. It does not find other types of breast cancer cells, such as those that are human epidermal growth factor receptor 2 (HER2) or progesterone receptor (PR) positive. 

How do I prepare for a PET Scan?

Your care team will talk with you about how to get ready for your PET scan, but in general:

  • Bring a list of the medications that you are taking, a brief medical history, and treatments that you have had (chemotherapy, radiation therapy, or surgery). 
  • If you take any medications for diabetes, you may be told not to take these, as they could affect the tracer. 
  • You will be told how long you need to fast (not eat) prior to the test. 
  • You should avoid exercise the day before, on the day of the scan, and until the scan is over.
  • You will need to lie still during the test, which could be 30-60 minutes long. Talk with your provider if you think you might have a hard time doing so. 

How is a PET scan done?

The test will take 2-3 hours, from start to finish. You will be given the tracer. The test will not start for about 60-90 minutes so that the tracer can move around your body. After this time, you will lie on a table that can slide into the scanner. The scanner is a donut-shaped machine. The scan takes 30-60 minutes and you will need to lie still. You may receive a medication to help you relax.  How long the test takes depends on how much of the body is being scanned. You will be able to talk with the technician during the test.

What should I expect after the PET scan?

If you received medication to help relax, you will need someone to drive you home. You can go back to your normal diet and activity the next day. People do not often have any side effects from the tracer. You should drink plenty of water to clear the tracer from your body. 

How do I get the results of my PET scan?

A specialist will review the results of your PET scan and send a report to your provider. Your provider will go over the results with you.

If your provider has ordered a PET scan for you, be sure to ask any questions you may have. Talk with your team about why the scan was ordered, how you should prepare, what to expect the day of, and how and when you will get your results. 

References

Medline Plus. PET Scan. 2018. 

RadiologyInfo.org. PET/CT - Positron Emission Tomography/Computed Tomography

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