PET Scan

Written by Brian Krans | Published on July 10, 2012
Medically Reviewed by George Krucik, MD

What Is a PET Scan?

A positron emission tomography (PET) scan is an imaging test that allows doctors to check for disease in your body.

The scan uses radioactive tracers in a special dye. These tracers are injected into a vein in your arm and are then absorbed by your organs and tissues. When highlighted under a PET scanner, the tracers allow doctors to see how well your organs and tissues are working. The PET scan is able to measure blood flow, oxygen use, glucose metabolism (how your body uses sugar), and much more.

A PET scan is typically an outpatient procedure, meaning that you will be able to go about your day after the test is complete.

Why a PET Scan Is Performed

Your doctor may order a PET scan to inspect the blood flow, oxygen intake, and metabolism of your organs and tissues. PET scans are most commonly used to detect cancer, heart problems, brain disorders, and problems with the central nervous system. (Cleveland Clinic)

Unlike other imaging tests, such as CT or MRI scans, PET scans show abnormalities with tissues at the cellular level, which provides your doctor with the best view of complex systemic diseases, such as coronary artery disease, brain tumors, memory disorders, and seizures.

When used to detect cancer, the test allows doctors to see how the cancer metabolizes, how it may spread, and how well treatments are working.

Risks of a PET Scan

While the scan does involve radioactive tracers, the exposure to harmful radiation is minimal. According to the Mayo Clinic, radiation levels are too low to affect the normal processes of the body. The risks of the test are minimal compared with how beneficial the results can be in diagnosing serious medical conditions.

However, radiation is believed to be unsafe for developing fetuses, so women who are pregnant, think they may be pregnant, or are nursing should not undergo a PET scan.

Other risks of the test include feelings of discomfort if you are claustrophobic or are uncomfortable with needles.

How to Prepare for a PET Scan

Your doctor will provide you with complete instructions about how to prepare for your PET scan. Tell your doctor about any medications you are taking, whether they are prescription, over-the-counter, or supplemental.

You may be instructed not to eat anything for up to eight hours before your procedure. You will, however, be able to drink water.

If you are pregnant, or believe you could be pregnant, tell your doctor because the test may be unsafe for your baby. Also, tell your doctor about any medical conditions you have. For example, diabetics have special instructions for test preparation because fasting beforehand could affect their blood sugar levels. (Mayo)

You may be asked to change into a hospital gown. You will also need to remove all of your jewelry and/or body piercings because metal can interfere with the testing equipment.

How a PET Scan Is Performed

Before the scan, the tracers will be administered through an IV in your arm, through a solution you drink, or in a gas you inhale. Your body needs time to absorb the tracers, so you will wait about an hour before the scan begins.

Next, you will undergo the scan. This involves lying on a narrow table attached to the PET machine, which looks like a giant toilet paper roll. The table glides slowly into the machine so that the scan can be conducted.

You will need to lie still during the scan, and the technician will tell you when you need to remain still. You may be asked to hold your breath for short periods. You will hear buzzing and clicking noises during the test.

When all the necessary images have been recorded, you will slide out of the machine. The test is then complete.

After a PET Scan

After the test, you’ll be free to go about your day unless your doctor gives you other instructions. Drink plenty of fluids after the test to help flush the tracers out of your system. Generally, all tracers will have left your body after two days.

Meanwhile, a trained specialist will interpret the PET images and share the information with your doctor. Your doctor will go over the results with you at a follow-up appointment.

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