Childen's Hospital Boston 300 Longwood Avenue
Boston, MA 02115
(617) 355-6000
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My Child Has:
Brain PET
Programs that perform this procedure
Comprehensive Brain Malformation Program   Brain Tumor Program  
Division of Nuclear Medicine/PET   Division of Neuroradiology  
What is Brain PET?
PET and MRI image of brain
See enlarged image
PET (Positron Emission Tomography) is a safe, effective and non-invasive diagnostic imaging technique. It provides images that show chemical and functional changes within the brain. PET is very sensitive and it can detect changes in the brain associated with seeing, hearing and thinking. Similarly, it can detect changes in the brain associated with certain diseases that cannot be seen with other imaging methods.

For example, in patients with epilepsy, it can show which part of the brain is responsible for the seizures, even if the patient had a normal MR or CT of the brain. Another example: in patients who have been treated for brain tumors, PET helps define if the tumor is still growing or is inactive.

PET of the brain is obtained after the intravenous injection of a radiotracer (also called radiopharmaceutical). The most commonly used PET brain radiopharmaceutical is a substance similar to sugar or glucose and it is called fluorodeoxyglucose (FDG), which is labeled with a radioisotope called fluorine-18 (18F). This radioisotope has a short physical half-life (T1/2 = 111 minutes). For short, this radiopharmaceutical is called 18F-FDG.

Once injected, FDG rapidly (30-40 minutes) localizes in the brain. The brain consumes large amounts of glucose and FDG will localize on the corresponding regions of the brain. Once FDG is in the brain, images are obtained using an imaging device called a PET scanner. The PET scanner obtains 3-D images of glucose in the brain that helps physicians diagnose certain disorders.

Why would my doctor request a Brain PET?
A Brain PET is useful in various conditions, including:
  • Localization of the source of epilepsy
  • Assessment of the function of brain tumor
  • Determination of the effectiveness of surgery, radiation therapy and/or chemotherapy in brain tumors
  • Assessment of brain damage due to trauma
How to prepare for a Brain PET?
  • Arrive on time for your child's appointment. Tardiness may result in rescheduling.
  • Actual imaging time will be approximately one half hour, but you and your child should plan to be with us for approximately one and one half hours.
  • Do not ingest any form of caffeine (including soda, tea and chocolate), nicotine or alcohol 12 hours prior to the PET scan.
  • No solid food or fluids four hours prior to the PET scan. Patients are allowed to drink water. Your/your child may take any medications that you/he/she normally take(s) the morning of the exam.
  • Wear warm and comfortable clothes.
  • If MR and/or CT scans have been done at a facility other than Children's Hospital Boston, please bring those images with you. The nuclear medicine physician will compare the MR and CT scan to the PET scan.
  • If you/your child's doctor has given you a requisition for the exam, please bring it with you. If we have to call the doctor's office to get the requisition after you have arrived for the appointment, this will cause a delay in performing the scan.
  • If you/your child is scheduled for sedation or if you think sedation is necessary (to hold still) and a nuclear medicine staff member has not contacted you, please call us at 617-355-7010 for specific instructions.
How is a Brain PET performed?
Image of girl preparing for a PET scan When you arrive, a technologist will greet you and explain the procedure in detail. Obtaining a PET scan involves three steps: injection of a radiopharmaceutical, a waiting period, and scanning by the PET machine.
  1. Radiopharmaceutical. You/your child will be injected with the radiopharmaceutical. This substance contains very small amounts of radioactive molecules. It will not cause any sensation or negative effects.

    The type of radiopharmaceutical selected is designed to go to the part of the body that is being tested.

    Once the radiopharmaceutical reaches the brain, it will transmit signals (gamma rays) that can be detected from outside the body by the PET scanner.

  2. Waiting period. After the injection, you/your child must wait for 30 to 60 minutes in a separate room. During this time, while the radiopharmaceutical is circulating within the body, it is extremely important for you/your child to be very quiet; no talking, reading or sleeping. These activities can change the radiopharmaceutical distribution in the brain and thus affect the image. The lights in the room will be dim to help you/your child relax.

  3. PET scanning. After the waiting period, the technologist will bring you/your child into the PET suite. You/your child will be asked to lie on the imaging table and remain still while the images are taken. Parents or family members are allowed to sit in the room during imaging. The technologist will be watching the procedure through the window and by TV monitor. You/your child will be in the scanner from 15-20 minutes. While you/your child lies within the scanner, a computer will create images of your brain.
What can be expected during the procedure?
You/your child may experience some discomfort associated with the insertion of the intravenous needle. The needle used for the procedure is small. Once the radiopharmaceutical is injected, the needle is withdrawn and a gauze bandage with adhesive tape is placed over the site of the injection. The area where the injection was given may be a little sore.

Although the camera may appear large and intimidating, it does not touch you/your child.

What happens after the Brain PET?
Once the study is complete, it will be evaluated for quality. If there was too much motion, the study may need to be repeated. If there was no motion, you/your child will be free to leave and resume normal activity.
How are the results of the study obtained?
The images will be processed and then the nuclear medicine physician will evaluate and interpret the study and promptly inform you/your child's referring physician of the results.
How can additional information be obtained?
For more information about Nuclear Medicine/PET, please contact us at:

Division of Nuclear Medicine/PET
Children's Hospital Boston
300 Longwood Avenue, Pavilion 2
Boston, MA 02115
Main Number: 617-355-7010
Fax Number: 617-730-0623
Business hours: Monday through Friday, 8 a.m. - 5 p.m.

How is an appointment scheduled?
To schedule an appointment please contact your referring physician as their office must schedule it for you. If you currently have an appointment and need to reschedule or are unable to make the appointment, please call us at least 48 hours in advance at 617-355-7010.
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