A positron emission tomography (PET) scan is an imaging test that allows your doctor to check for diseases in your body.
The scan uses a special dye containing radioactive tracers. These tracers are either swallowed, inhaled, or injected into a vein in your arm depending on what part of the body is being examined. Certain organs and tissues then absorb the tracer.
When detected by a PET scanner, the tracers help your doctor to see how well your organs and tissues are working.
The tracer will collect in areas of higher chemical activity, which is helpful because certain tissues of the body, and certain diseases, have a higher level of chemical activity. These areas of disease will show up as bright spots on the PET scan.
The PET scan can measure blood flow, oxygen use, how your body uses sugar, and much more.
A PET scan is typically an outpatient procedure. This means you can go about your day after the test is finished.
In the United States, around 2 million PET scans are performed each year.
Why is a PET scan performed?
Your doctor may order a PET scan to inspect your blood flow, your oxygen intake, or the metabolism of your organs and tissues. PET scans show problems at the cellular level, giving your doctor the best view of complex systemic diseases.
PET scans are most commonly used to detect:
- heart problems
- brain disorders, including problems with the central nervous system (CNS)
Cancer cells have a higher metabolic rate than noncancerous cells. Because of this high level of chemical activity, cancer cells show up as bright spots on PET scans. For this reason, PET scans are useful both for detecting cancer and for:
- seeing if the cancer has spread
- seeing if a cancer treatment is working
- checking for a cancer recurrence
However, these scans should be read carefully by your doctor, as it’s possible for noncancerous conditions to look like cancer on a scan. It’s also common for solid tumors to fail to appear on PET scans.
PET scans reveal areas of decreased blood flow in the heart. This is because healthy heart tissue will take in more of the tracer than unhealthy tissue or tissue that has decreased blood flow.
Different colors and degrees of brightness on the scan will indicate different levels of tissue function, helping you and your doctor decide how best to move forward.
Glucose is the main fuel of the brain. During PET scans, tracers are “attached” to compounds such as glucose. By detecting radioactive glucose, the PET scan is able to detect which areas of the brain are utilizing glucose at the highest rates.
Your doctor will look at the scan to see how the brain is working and to check for any abnormalities.
PET scans are used to help diagnose and manage many central nervous system (CNS) disorders, including:
- Alzheimer’s disease
- head trauma
- Parkinson’s disease
What risks are involved with a PET scan?
The PET scan involves radioactive tracers, but the exposure to harmful radiation is minimal. According to the Mayo Clinic, the amount of radiation in the tracer is small, so the risks to your body are low. Still, it’s a good idea to discuss possible risks with your doctor.
The risks of the test are also minimal in comparison to how beneficial the results can be in diagnosing serious medical conditions.