Home > Health Library > Positron Emission Tomography (PET)
Positron emission tomography (PET) is a test
that uses a special type of camera and a
tracer (radioactive chemical) 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
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.
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
A PET scan is often used to evaluate cancer, check blood
flow, or see how organs are working.
positron emission tomography (PET) scan is done
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
center by a
nuclear medicine specialist and a technologist. You
will lie on a table that is hooked to a large scanner, camera, and
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 centers,
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
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 1
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 who is doing the test.
You may feel nervous inside the PET
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
Positron emission tomography (PET) is a
test that uses a special type of camera and a
tracer (radioactive chemical) to look at organs in 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
Areas of increased glucose metabolism may mean
a tumor 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.
Hendel RC, et al. (2009).
ACCF/ASNC/ACR/AHA/ASE/SCCT/SCMR/SNM 2009 appropriate use criteria for cardiac
radionuclide imaging. Circulation, 119(22):
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.
Current as of:
January 28, 2014
Adam Husney, MD - Family Medicine & Howard Schaff, MD - Diagnostic Radiology
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