Positron emission tomography (PET) scan before epilepsy surgery

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Find out how a PET scan helps identify where seizures start in the brain.

Key points

A PET scan takes pictures of how the brain builds up and breaks down substances to identify where seizures start.
Your child cannot eat, drink or chew gum for four hours before the scan. The test may be cancelled if their blood sugar level is too high.
During the scan, your child will be injected with a tiny amount of radioactive liquid and lie still in the PET scanner while electrodes attached to their scalp record brain activity.
You may discuss the results of the PET scan with your child's doctor about four to six weeks after the test.

Introduction

A positron emission tomography (PET) scan takes pictures of the brain’s metabolism (how it builds up and breaks down materials) to identify where seizures start.

About the test

The PET scanner is a large machine with a tunnel in the centre. During the scan, your child will lie on a narrow table that slides into the tunnel.

The scan takes one to two hours, including preparation. If your child needs a sedative (medicine to keep them calm) for the PET scan, please allow up to three hours for your hospital visit. This allows enough time for the scan and for any medicine to wear off before your child goes home.

Why does my child need a PET scan?

The PET scan will tell the doctor where seizure starts in the brain. It will provide additional information to clarify or confirm the location of seizures, especially in patients where other tests such as EEG or MEG are not clear, when an MRI is normal or when the MRI findings are unclear.

Risks of the test

Does the test have any risks or side effects?

There is a low risk from the radioactive liquid your child receives for the PET scan. The dose of liquid that is given to your child equals about two to four years of natural background radiation, depending on your child’s age and weight. Your child’s body will break down the radioactive liquid very quickly and pass it out in urine within 24 hours.

The potential benefits of the PET scan outweigh any potential risk from the radiation.

Preparing for the test

How do I prepare my child for a PET scan?

Explain what will happen during the PET scan in words your child understands.
Do not let your child eat, drink or chew gum for four hours before the test. If your child has diabetes, contact the PET team for special instructions.
Give your child any required medication as usual with a small amount of water, unless your child’s doctor tells you otherwise.
Make sure your child’s hair is freshly washed. Check it for any signs of head lice and tell the nurse at the hospital if you see anything.
To help the electrodes stay in place during the test, do not use conditioner or styling products in your child's hair after you wash it.

Will my child need to be sedated for a PET scan?

Some children may need to take a mild sedative to help them lie still for the full scan.

Test

What happens when my child arrives for the PET scan?

Your child will have a small needle prick in their finger so the nurse can check their blood sugar level. If the level is too high, the test will be cancelled and you will need to make another appointment.
If the blood sugar level is acceptable, your child will then be injected with a very small amount of radioactive liquid. This liquid helps to show where abnormal metabolism is happening in the brain.
The technologist may place EEG electrodes on your child’s scalp.
Your child will need to wait about 30 to 45 minutes for the injected liquid to flow to their brain. During this time, they will be in a quiet, darkened room to let them relax. You are free to wait with them in this room.
When this time has passed, the technologist will ask your child to empty their bladder in the washroom so that they can lie comfortably during the PET scan.
Your child will then go into the PET room.

What happens during a PET scan?

During the PET scan, your child will lie inside the scanner tunnel and will stay very still and quiet while the scanner takes pictures of their brain.

The PET scan itself takes about 30 minutes. The PET technologist will watch the scan through a window and a TV camera.

May I stay with my child during the PET scan?

Yes, you may stay with your child during the scan.

After the test

What should I expect after the PET scan?

When the scan is done, you and your child may go home.

If your child took any sedative for the PET scan, they may leave the hospital only when they are alert and fully recovered. Afterwards, they may eat, drink and return to their usual activities.

Follow-up care

When will I get the results of the scan?

Your doctor will receive the PET scan results and discuss them with you and your child at a follow-up appointment, usually four to six weeks after the scan.

At SickKids

If your doctor has told you that your child needs a sedative for the PET scan, someone from the nuclear medicine department will contact you with instructions on when your child needs to stop eating and drinking before their appointment.

If the PET is booked without arranging a sedative, but you think your child will need it, please contact the nuclear medicine department at 416-813-7654 ext. 206065.

Last updated: M10 10th 2017