Brain PET Scan

How to Prepare for the Test

You may be asked not to eat anything for 4 to 6 hours before the scan. You will be able to drink water.

Tell your health care provider if:

• You are afraid of close spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious.
• You are pregnant or think you might be pregnant.
• You have any allergies to injected dye (contrast).
• You have taken insulin for diabetes. You will need special preparation.

Always tell your health care provider about the medicines you are taking, including those bought without a prescription. Sometimes, medicines interfere with the test results.

How the Test will Feel

You may feel a sharp sting when the needle containing the tracer is placed into your vein.

A PET scan causes no pain. The table may be hard or cold, but you can request a blanket or pillow.

An intercom in the room allows you to speak to someone at any time.

There is no recovery time, unless you were given a medicine to relax.

Why the Test is Performed

A PET scan can show the size, shape, and function of the brain, so your doctor can make sure it is working as well as it should. It is most often used when other tests, such as MRI scan or CT scan, do not provide enough information.

This test can be used to:

• Diagnose cancer
• Prepare for epilepsy surgery
• Help diagnose dementia if other tests and exams do not provide enough information
• Tell the difference between Parkinson disease and other movement disorders

Several PET scans may be taken to determine how well you are responding to treatment for cancer or another illness.

Normal Results

There are no problems detected in the size, shape, or function of the brain. There are no areas in which the tracer has abnormally collected.

What Abnormal Results Mean

Abnormal results may be due to:

• Alzheimer disease or dementia
• Brain tumor
• Epilepsy, and may identify where the seizures start in your brain
• Movement disorders (such as Parkinson disease)

Risks

The amount of radiation used in a PET scan is low. It is about the same amount of radiation as in most CT scans. Also, the radiation does not last for long in your body.

Women who are pregnant or are breastfeeding should let their doctor know before having this test. Infants and babies developing in the womb are more sensitive to the effects of radiation because their organs are still growing.

It is possible, though very unlikely, to have an allergic reaction to the radioactive substance. Some people have pain, redness, or swelling at the injection site.

Considerations

It is possible to have false results on a PET scan. Blood sugar or insulin levels may affect the test results in people with diabetes.

PET scans may be done along with a CT scan. This combination scan is called a PET/CT.

References

Hutton BF, Segerman D, Miles KA. Radionuclide and hybrid imaging. In: Adam A, Dixon AK, Gillard JH Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 6th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2015:chap 6.

Meyer PT, Rijntjes M, Weiller C. Neuroimaging: Functional neuroimaging. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley's Neurology in Clinical Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 33C.