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Frequently Asked Questions
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General
Who should get a PET scan?
Your primary care physician or your referring specialist will be the best judge
of that. PET scans are particularly useful in diagnosing many types of cancer,
including ovarian, lung , brain, and skin; coronary heart disease; and all types
of neurological problems, such as epilepsy and Alzheimer's disease. For
children, PET is a powerful tool for diagnosing brain tumors, other cancers, and
epilepsy.
What's the difference between PET and other imaging modalities such as
CT scan and MRI?
A PET scan produces images of metabolic activity as opposed to images of the
body's physical structures that are derived from these other imaging tests.
This is important because functional changes often predates structural changes
in tissues. PET images may therefore demonstrate changes long before they would
be revealed by modalities like CT and MRI.
How does PET work?
For a PET scan, a small amount of radioactivity is attached to biological
substances that are similar to those already found in the body. These
radioactive agents, once introduced to the body, are processed by organs and
tissues as part of their normal function. The PET scanner is able to detect the
location of the radiation in the body. A computer then creates a picture of the
activity using colors to highlight the different levels of function. The unique
information that PET provides is extremely useful to your physician in making
decisions regarding your future care and medical treatment.
What does a PET scan do for someone diagnosed with cancer or another
serious illness?
PET can effectively pinpoint the source of many of the most common cancers and
give physicians important early information about heart and neurological
diseases, eliminating the need for redundant tests and diagnostic surgical
procedures.
How much radiation does a PET scan expose the patient being scanned?
Because the radioisotope used in a PET scan is short- lived, the amount of
radiation exposure the patient receives is the same as from two chest X-rays.
What is the PET scan procedure like?
In most cases, a PET scan will begin with an injection of the radioisotope agent
into the patient's arm. The patient will be asked to rest quietly for a short
period of time as the tracer circulates throughout the body. Then the patient
will be positioned on a scanning bed and scanned. As the images of the body are
obtained, the patient will be asked to remain very still. The imaging time
varies with the procedure, but generally takes about one hour.
Do people experience any reactions as a result of a PET scan?
Patients typically do not experience any reactions as a result of the PET scan,
because the tracer material is processed by the body naturally. Therefore, no
side effects are expected.
Is PET painless?
Yes, after the injection of a minute amount of the trace solution into the
patient's arm, the patient relaxes while the scan is performed.
What are the clinical applications of PET?
Traditionally, PET has been used in oncology (the study of tumors), neurology
(the study of diseases and disorders of the nervous system), and cardiology (the
study of diseases and functioning of the heart ). PET provides the physician
with information about the body's chemistry not available through any other
procedure. Unlike Computed Tomography (CT) or Magnetic Resonance Imaging (MRI),
which look at anatomy, PET evaluates metabolic activity. PET is quickly becoming
a leading diagnostic tool used to detect all types of cancer.
What should I do if my doctor won't refer me for a PET scan?
Seek a second opinion or ask that your doctor speak with a nuclear medicine
physician. By learning more about PET, you can explain to your doctor why you
want a PET scan.
I've only heard about PET scans recently. Are they new?
PET has been investigated for more than 30 years. However, only until recently,
few institutions had access to this powerful diagnostic tool. As the technology
expands, this diagnostic tool is becoming more mainstream. Clinical trials have
demonstrated the utility of this modality, moving it from the research
environment to the clinic environment.
How do I prepare for a PET scan?
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List of medications
Patients should bring a list of the medications they are taking.
Patients should also bring all previous studies, including CT
and/orn MR films and reports, as well as their chemotherapy history,
including date of most recent treatment, with them.
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Fasting
Patients must fast overnight prior to a PET scan. Afternoon patients
may eat a light meal six hours prior to exam. Patients should drink
water before beginning fast and drink lots of water after beginning
fast. Continue to hydrate. Oncology patients must fast overnight, or
at least 6 hours prior to PET scan.
Cardiology patients may eat a light breakfast. It must be low fat.
Diabetic patients may eat normal, low fat meals, and take usual
insulin dose.
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Exercise
Patients should AVOID excessive exercise for 3 days prior to test.
What happens during the test?
After you register, you will be escorted to the PET prep room. The
radioisotope or FDG is injected into the patient. When it is time for the PET
scan to begin, you will lie on a table that slides into the scanner, a
donut-shaped machine that resembles a CT scanner. The table will slide through
the PET scanner. The painless procedure can take from one to two hours.
How Does PET work?
A compound called fluorodeoxyglucose (FDG) is injected into patient and is
absorbed in the same manner as normal glucose. FDG is formed by taking glucose
and attaching radioactive fluorine molecules. This is a relatively painless
procedure involving the injection of a small amount of the trace into a
patient's vein.
Different tissues absorb more FDG than others. Cancer cells, for example,
typically have higher metabolic rates because they are growing faster than
normal cells and thus absorb more FDG than normal cells. The way different kinds
of cells absorb FDG can tell a radiologist whether or not certain diseases are
present in a patient's body.
After the PET scan, a PET physician will interpret your scan and transmit the
information to your referring physician so that the most appropriate course of
treatment can be charted.
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