PET Scan (Positron Emis­sion Tomography)

MUHC, 2005

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What is PET scanning?

Positron Emis­sion Tomog­ra­phy is a tech­nol­ogy that com­bines med­i­cine, phys­i­ol­ogy, chem­istry, physics and com­put­ers and allows us to image the “work­ing” part of the brain as well as other organs of the body.

At the MNIH, PET is used to look at cere­bral blood flow, to iden­tify and mon­i­tor neu­ro­log­i­cal dis­or­ders such as Parkinson’s dis­ease, and for pre-​surgical eval­u­a­tion of patients with epilepsy and brain tumours.

The PET scan­ner uti­lizes radi­a­tion emit­ted as positrons in a con­scious patient’s brain to cre­ate images or pic­tures of dis­tinct areas.

Unlike MRI or CT, PET does not show the body’s anatomy but rather the chem­i­cal func­tion or metab­o­lism of an organ.

The dose of radi­a­tion received from a PET scan is approx­i­mately twice the annual amount you can expect to receive from nat­ural sources.

Preg­nant and nurs­ing women should speak to staff and chil­dren under the age of 18 should be accom­pa­nied by an adult.


You may be asked not to eat or drink for a few hours before the scan. If this is not required, please eat and drink mod­er­ately on the day of your test.

If you have any ques­tions prior to your appoint­ment you should feel free to call the Brain Imag­ing Centre.

When you arrive at the Cen­tre, the staff will explain the PET pro­ce­dure to you. It is impor­tant to inform the staff of your cur­rent med­ical sta­tus, such as whether you are dia­betic or are tak­ing any medication.

Please take your med­ica­tions on the day of the test.

You should wear warm, com­fort­able cloth­ing, as the room can be cold at times. Your clothes should allow the rolling up of sleeves and not restrict cir­cu­la­tion. If pos­si­ble, before com­ing to the hos­pi­tal, remove hair­pins, ear­rings, and any metal that may show on the scan. For your com­fort you will be asked to go to the bath­room before start­ing your scan.

Scan dura­tion ranges between 20 min­utes to 2 hours and 30 min­utes depend­ing on the type of exam­i­na­tion.

What hap­pens dur­ing a PET scan?

You will be asked to lie down and place your head in a cradle-​like appa­ra­tus sim­i­lar to what you would find in a CT or MRI scan­ner. Please try to be as still as pos­si­ble. To assist in this, there is a bag filled with poly­ester beads which con­forms to the shape of your head. This also pro­vides sup­port and com­fort. You will have a Vel­cro strap around your fore­head and it is impor­tant to note that only part of your head will be inserted into the scan­ner. The scan­ner is rel­a­tively quiet. Dur­ing the scan please close your eyes, limit your move­ment as much as pos­si­ble, and speak only in response to questions.

As the scan starts, a small amount of a radioac­tive com­pound will be injected into a vein of the arm or an intra­venous site. The sub­stance is not a dye, but a com­pound your body uses like water or sugar that has a small radioac­tive tag. This allows the imag­ing of spe­cific parts of the brain.

Through­out the scan, qual­i­fied per­son­nel will be present.

After the scan

There should be no side effects, and you should be able to go about your nor­mal activ­i­ties after the scan. In some instances you may be asked to drink extra flu­ids. PET scan­ning does not inter­fere with other tests or treatments.

How do I get the results of my PET scan?

The scan will be read by a qual­i­fied physi­cian at the hos­pi­tal. The results will be sent to the physi­cian who ordered the scan and will take approx­i­mately one week.

What is the dif­fer­ence between a CT scan, an MRI scan and a PET scan?

PET, CT, and MRI use scan­ning devices and com­put­ers to con­struct images of the brain and other major organs in the body. The CT scan uses x-​rays, while MRI uses mag­netic and elec­tri­cal fields to show the struc­tures of the brain. In con­trast, PET shows how the brain cells are work­ing in rela­tion­ship to the func­tions they per­form. Hence, PET maps brain function.


PET (Positron Emis­sion Tomog­ra­phy):
A tech­nique that allows the mea­sure­ment of dis­tinct areas of brain func­tion. The PET scan­ner uti­lizes radi­a­tion emit­ted from the patient to cre­ate images or pic­tures of brain function.

MRI (Mag­netic Res­o­nance Imag­ing):
A tech­nique that uses elec­tro­mag­netic fields to cre­ate an image of the struc­ture of the brain or other organs.

CT (Com­put­er­ized Tomog­ra­phy):
The uti­liza­tion of x-​rays to cre­ate images of the struc­ture of the brain or other organs.

Radioac­tive Compound

Mate­ri­als that have been pro­duced and made radioac­tive in a med­ical cyclotron and are injected prior to the test. They are sim­i­lar to sub­stances that are nat­u­rally pro­duced or used by the body, such as sugar, water and oxygen.

McConnell Brain Imag­ing Cen­tre
Mon­treal Neu­ro­log­i­cal Institue and Hos­pi­tal
Tel. 5143981996
Web­ster 2B (sec­ond base­ment level)
Room 206

Authors: R. Fuka­sawa, P. Del Mas­tro
Pro­duc­tion: Neuro-​Patient Resource Cen­tre
Mon­treal Neu­ro­log­i­cal Hosp­tial Room 354
Tel: (514) 3985358
E-​mail: infoneuro@​muhc.​mcgill.​ca
Web site: http://​infoneuro​.mcgill​.ca/

This infor­ma­tion is for edu­ca­tional pur­poses only, and is not intended to replace the advice of a pro­fes­sional health­care prac­ti­tioner, or to sub­sti­tute for med­ical care.

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