Brain PET Scan

Written by Brian Krans | Published on August 15, 2012
Medically Reviewed by George Krucik, MD

What is a Brain PET Scan?

A brain positron emission tomography (PET) scan is an imaging test that allows doctors to see how your brain is functioning.

The scan captures images of the activity of the brain after radioactive “tracers” have been absorbed into the bloodstream. These tracers are “attached” to compounds like glucose (sugar). Glucose is the principal fuel of the brain. Active areas of the brain will be utilizing glucose at a higher rate than inactive areas. When highlighted under a PET scanner, it allows doctors to see how the brain is working and helps them detect any abnormalities.

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

Why a Brain PET Scan Is Done

The test accurately details the size, shape, and function of the brain.

Unlike other scans, a brain PET scan allows doctors a view of not only the structure of the brain, but how it is functioning, as well.

This allows doctors to:

  • check for cancer
  • determine if cancer has spread to the brain
  • diagnose dementia or Alzheimer’s
  • differentiate between Parkinson’s disease and other conditions
  • prepare for epilepsy surgery

Your doctor may have you undergo a brain PET scan regularly if you are undergoing treatment for brain disorders. This can help him or her monitor the success of your treatment.

How to Prepare for a Brain PET Scan

Your doctor will provide you with complete instructions to help you prepare for your brain PET scan. Alert your doctor to any medications you may be taking, whether they are prescription, over-the-counter, or even nutritional supplements.

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—the test might be unsafe for your baby. You should also tell your doctor about any medical conditions you may have. For example, diabetics will likely be given special instructions for the test, as the fasting beforehand could negatively affect their blood sugar levels.

Immediately before the test, you may be asked to change into a hospital gown and remove all of your jewelry and body piercings.

Of course, you want to plan your day around your appointment as well.

How a Brain PET Scan Is Performed

You’ll be brought into the procedure room and seated in a chair. A technician will insert an IV into your arm. Through this IV, a special dye with radioactive tracers will be injected into your veins. Your body needs time to absorb the tracers as blood flows through the brain, so you will wait before the scan begins. This typically takes about an hour.

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 and smoothly into the machine so the scan can be completed.

You will have to lie still during the scans. The technician will tell you when you need to remain motionless. The scans record brain activity as it is happening. These can be recorded as video or as still images. The tracers are concentrated in areas of increased blood flow.

When the desired images are stored in the computer, you will slide out of the machine. The test is then complete.

Following Up After a Brain PET Scan

It’s a good idea to drink plenty of fluids after the test to help flush the tracers out of your system. Generally all tracers are out of your body after two days.

Other than that, you are free to go about your life unless your doctor gives you other instructions.

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

Interpreting the Results of a Brain PET Scan

The images of brain PET scans appear as multicolored images of the brain, ranging from dark blue to deep red. Areas of active brain activity come up in warmer colors, such as yellow and red. Your doctor will look at these scans and check for abnormalities.

For example, a brain tumor will show up as darker spots on the PET scan. A patient with Alzheimer’s and other forms of dementia will have larger-than-normal portions of their brain appear darker on the scan. In both of these cases, the dark areas signify areas of the brain that are impaired.

Your doctor will go over your personal scan to explain what the results mean and what will be the next course of action.

The Risks of a Brain PET Scan

While the scan does use radioactive tracers, the exposure is minimal. It’s too low to affect the normal processes of the body, according to the Mayo Clinic.

The risks of the test are minimal compared with how beneficial the results can be.

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

Other risks include uncomfortable feelings if you are claustrophobic or are uncomfortable with needles.

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