Neurology

Strong Epilepsy Center

Tests - Positron Emission Tomography (PET) Scan

What is a PET scan ?

A PET scan allows us to measure the way different areas of the brain function. The major advantage of the PET scan is that it can show changes in brain activity that occur quickly, in seconds.

What happens during a PET scan?

A small amount of a radioactive material, which is mixed with a substance that resembles sugar or glucose, is injected in your arm or inhaled as a gas. The type of radioactive material selected determines whether you will inhale it or receive it by injection. Different substances are chosen for different types of studies. As the sugar-like substance is metabolized by your brain, radiation that is produced from this material is detected by the PET scanner. The information gathered by the scanner is fed into a computer, and the result is a complex picture of your individual brain.

How does PET compare to a regular X-ray, a CT scan, or an MRI?

A conventional X-ray is made by firing x-rays through a person and onto a film. The image produced is a shadow which shows some of the structures in a person's body, such as bone and cartilage.

A CT scan fires fine streams of x-rays through the body from several different directions. A composite picture of a person's anatomy is the result. Then, the composite picture is sliced to show the details of one piece of the structure.

An MRI does the same thing as a CT scan, but it uses magnetic and radiowave fields to make a picture of the structure of the brain.

X-rays, CT and MRI scans show the structure of the brain. A PET scan shows how the brain functions.

A PET scan uses the radiation that comes from the patient to develop images. The other procedures send either x-rays or magnetic and radiowaves through the body.

How do I prepare for a PET scan?

Eat a light meal the evening before the scan. Do not eat or drink the morning of the test. Your doctor may give you other instructions for the particular type of radiopharmaceutical you will receive.

Is a PET scan painful?

You will be lying on a comfortable couch with your head inside a large, doughnut-shaped structure, the Positron Emission Tomograph. You must keep your head still. The only discomfort is from the prick of the needle if the radiopharmaceutical is injected.

What does a PET scan show?

In patients with epilepsy, the PET commonly shows decreased function in the area of the brain where the seizures come from. Most PET scans are done when the patient is not having a seizure. An EEG may be done during the PET scan to determine seizure activity.

How will I feel after a PET scan?

You should not feel any adverse effects from the PET scan. However, some patients have allergic reactions. Please let your doctor know, ahead of time, if you have allergies. The radiation from this procedure is the same or less than a conventional X-ray.