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.
Why It Is Done
positron emission tomography (PET) scan is done
- Study the brain's blood flow and
metabolic activity. A PET scan can help a doctor find
nervous system problems, such as
transient ischemic attack (TIA),
amyotrophic lateral sclerosis (ALS),
- Find changes in the brain
that may cause
- Evaluate some cancers, especially
lymphoma or cancers of the head and neck, brain, lung, colon,
or prostate. In its early stages, cancer may show up more clearly on a PET scan
than on a CT scan or an MRI.
- See how advanced a cancer is and
whether it has spread to another area of the body (metastasized). It is often
necessary to do both CT and PET scans to evaluate cancer.
- Help a
doctor choose the best treatment for cancer or to see how well treatment is working. PET scans may also be done to see
whether surgery can be done to remove a tumor.
- Help diagnose Alzheimer's disease when the symptoms are not clear or when a person has dementia symptoms at a young age (usually younger than 65).1 This is called amyloid imaging.
- Find poor blood flow
to the heart, which may mean
coronary artery disease.
- Find damaged
heart tissue, especially after a
- Help choose the best
treatment, such as
coronary artery bypass graft surgery, for a person
with heart disease.