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Positron Emission Tomography (PET) is a nuclear
medicine procedure that produces pictures of the
body’s biological functions. PET is a unique
diagnostic imaging modality that is capable of
detecting certain diseases before other imaging
modalities such as: computed tomography (CT) and
magnetic resonance imaging (MRI). PET is able
to capture chemical and physiological changes
related to metabolism, as opposed to gross anatomy
and structure, which is obtained by CT and MRI.
This is important since function changes are often
present before structural changes in tissues.
PET images may therefore demonstrate pathological
changes long before they would be evident in CT
or MRI.
Your physician will advise on eating or drinking
prior to your exam, but typically, you will be
asked not to eat or drink anything four to six
hours before the exam. During the exam itself,
you should wear comfortable clothes and take any
prescribed medications on the day of the exam
unless instructed not to do so by your physician.
This will depend on the type of study, but typically,
you will be asked not to eat or drink anything
four to six hours before the exam. If you are
a diabetic, please notify the individual who is
scheduling your PET exam. Special arrangements
may need to be made in advance.
Before the scan, you will be injected with a radioactive
tracer. The tracer is a compound such as sugar,
labeled with a short-lived radioisotope. Once
injected, you will be asked to rest for approximately
thirty to forty-five minutes while the radioactive
compound distributes throughout your body, and
is processed by the organs being evaluated. The
radiation exposure associated with PET is safe
and much lower than that associated with conventional
CT scanning. The technologist will ask you to
lie on the scanner table, which will then slowly
pass through the PET scanner. The PET scanner
detects and records the signals the tracers emit.
The signals are then reassembled into actual images
through a computer.
A radiopharmaceutical is a radioactive drug. The
most commonly used PET radiopharmaceutical is
FDG, which is a radioactive form of glucose (sugar).
Radiopharmaceuticals are produced by physicists
and chemists.
FDG (Fluoro Deoxyglucose
is a type of glucose (sugar) and is the most commonly
radiopharmaceutical used in PET. To begin the
PET procedure a small amount of glucose is injected
into a patient's bloodstream. There is no danger
to you from this injection. Glucose is a common
substance that every cell in your body needs in
order to function. Diabetic patients need not
worry; it would take 1,000,000 doses of FDG to
equal the glucose in 1 teaspoon of sugar.
FDG has a half-life of approximately 110 minutes
and is excreted by way of the kidneys, so it is
quickly expelled from your body. FDG must pass
multiple quality control measures before it is
used for any patient injection.
There are no known side effects associated with
PET scanning. The injection is made up of radioactive
glucose (sugar).
A PET scan provides an approximately equivalent
amount of radiation exposure as several chest
x-rays. To put this into perspective, the average
person typically is exposed to the rough equivalent
of 5-6 chest x-rays per year just through normal
daily activities.
Every PET exam is different, but most patients
can expect to be at the hospital or imaging center
for at least two hours. This includes the time
needed for the injected tracer to distribute throughout
your body, as well as the time you actually spend
moving through the PET scanner. The exact length
of your exam will be determined by the type of
study being performed.
After your scan, you will get up from the scanner
bed and check out with the receptionist. You should
feel fine following your PET scan. There are no
known side effects from the injected tracer. You
will be notified when your results will be available
to your physician.
Your PET scan will be reviewed by a radiologist
or nuclear medicine physician. The radiologist
or nuclear medicine physician will send a report
to your physicians, who will give you the results
of the scan.
No, there are no known side effects to having
a PET scan performed. The only pain involved is
the needle prick when you receive the radiopharmaceutical
injection, which doesn't differ from any other
type of injection.
Yes and no. There are some molecular imaging tests
nuclear medicine tests, like Gallium 67 (used
for Lymphoma imaging) that are used in oncology
but there is no other biological imaging test
that provides the sensitivity, specificity, accuracy
and whole body tomographic surveying capabilities
of PET.
CT and MRI, for example,
both examine the anatomical (physical) structure.
Therefore, they can be useful in determining the
size and location of a tumor; however, neither
of them can determine the tumor's viability, whereas
PET can determine whether a tumor is still active.
If your physician doesn't know about PET, you
can direct them to this website for additional
information. You can have additional information
mailed to your physician by clicking
here and filing
out the attached form with their contact information.
.
PET has been used clinically for the last 14 years
but Medicare has only recently begun reimbursing
for the studies. Because of the reimbursement
issues many physicians did not know or fully understand
the benefits of a PET scan.
Approximately 350,000 PET scans will be performed
in 2002. The numbers of scans are increasing dramatically,
now that PET is no longer only for research purposes.
It is estimated that within the next five years,
in excess of 2,000,000 PET scans will be performed
per year. |
