Positron emission tomography (PET)
is a test that uses a special type of camera and a tracer (radioactive substance) to look at organs in the body. The tracer usually is a special form of a substance (such as glucose) that collects in cells that are using a lot of energy, such as cancer cells.
During the test, the tracer liquid is put into a vein (intravenous, or IV) in your arm. The tracer moves through your body, where much of it collects in the specific organ or tissue. The tracer gives off tiny positively charged particles (positrons). The camera records the positrons and turns the recording into pictures on a computer.
PET scan pictures
do not show as much detail as computed tomography (CT) scans or magnetic resonance imaging (MRI) because the pictures show only the location of the tracer. The PET picture may be matched with those from a CT scan to get more detailed information about where the tracer is located.
A PET scan is often used to evaluate cancer, check blood flow, or see how organs are working.
A positron emission tomography (PET) scan is done to:
You may be asked to sign a consent form.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done or what the results mean. To help you understand the importance of this test, fill out the medical test information form( What is a PDF document? ).
A positron emission tomography (PET) scan is done in a hospital nuclear medicine department or at a special PET centre by a radiologist or nuclear medicine specialist and a technologist. You will lie on a table that is hooked to a large scanner, camera, and computer.
The radioactive tracer is usually given in a vein (IV). You may need to wait 30 to 60 minutes for the tracer to move through your body. During this time, you may need to avoid moving and talking.
The PET scanner, which is shaped like a doughnut, moves around you. The scanned pictures are sent to a computer screen so your doctor can see them. Many scans are done to make a series of pictures. It is very important to lie still while each scan is being done. At some medical centres, a CT scan will be done at the same time.
For a PET scan of the brain, you will lie on a bed. You may be asked to read, name letters, or tell a story, depending on whether speech, reasoning, or memory is being tested. During the scan, you may be given earplugs and a blindfold (if you do not need to read during the test) to wear for your comfort.
If you are having a PET scan of your heart, electrodes for an electrocardiogram (EKG, ECG) will be put on your body.
During the test, you will be alone in the scanner room. The technologist will watch you through a window and you will be able talk to him or her through a two-way intercom at all times.
The test takes 2 to 3 hours.
After the test, drink lots of fluids for the next 24 hours to help flush the tracer out of your body.
You will not feel pain during the test. The table you lie on may be hard and the room may be cool. It may be difficult to lie still during the test.
You may feel a quick sting or pinch when the IV is put in your arm. The tracer is unlikely to cause any side effects. If you don't feel well during or after the test, tell the person doing the test.
You may feel nervous inside the PET scanner.
There is always a slight chance of damage to cells or tissue from radiation, including the low levels of radiation used for this test. But the chance of damage is usually very low compared with the benefits of the test.
Most of the tracer will be flushed from your body within 6 to 24 hours. Allergic reactions to the tracer are very rare.
In rare cases, some soreness or swelling may develop at the IV site where the radioactive tracer was put in. Apply a moist, warm compress to your arm.
Positron emission tomography (PET) is a test that uses a special type of camera and a tracer (radioactive substance) to look at organs in the body.
The radiologist may discuss preliminary results of the PET scan with you right after the test. Complete results are usually available in 1 to 2 days.
Blood flow is normal and organs are working well. The flow and pattern of the tracer shows normal distribution in the body.
Areas of increased glucose metabolism may mean a tumour is present.
Reasons you may not be able to have the test or why the results may not be helpful include:
Johnson KA, et al. (2013). Appropriate use criteria for amyloid PET: A report of the Amyloid Imaging Task Force, the Society of Nuclear Medicine and Molecular Imaging, and the Alzheimer's Association. Alzheimer's and Dementia, 9(1): e1–e16.
Other Works Consulted
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
ByHealthwise StaffPrimary Medical ReviewerAdam Husney, MD - Family MedicineBrian D. O'Brien, MD - Internal MedicineE. Gregory Thompson, MD - Internal MedicineMartin J. Gabica, MD - Family MedicineKathleen Romito, MD - Family MedicineSpecialist Medical ReviewerHoward Schaff, MD - Diagnostic Radiology
Current as ofDecember 4, 2017
Current as of: December 4, 2017
Adam Husney, MD - Family Medicine
& Brian D. O'Brien, MD - Internal Medicine & E. Gregory Thompson, MD - Internal Medicine & Martin J. Gabica, MD - Family Medicine & Kathleen Romito, MD - Family Medicine & Howard Schaff, MD - Diagnostic Radiology
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