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Definition of PET |
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PET is an acronym
which stands for Positron Emission Tomography. PET is a
non-invasive imaging procedure (non-surgical) that allows
physicians to examine the heart, brain, breast, lung, or
any other targeted internal organ and detect its metabolic
( chemical ) makeup. Unlike a CT or MRI which takes images
of the body’s organs, a PET scan differs in its ability to
show metabolism and a variety of physiologic phenomena
like sugar metabolism, cerebral blood flow, oxygen
metabolism, and receptor sites which are used to identify
and diagnose various forms of cancer. PET is the most
highly effective way to record, identify, and diagnose many forms of biological disorders.
The PET Scanner at
the Queen’s Medical Center is a 32-ringed, state of the
art, optical camera. Although PET scanners are
becoming more prevalent worldwide, there are still relatively few,
and access to these highly sophisticated medical equipment
is limited. |
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How does
PET work? |
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The patient receives an injection of a
radioactive isotope tracer which travels to the specific
organ to be scanned. The most commonly used compound is a
sugar compound Fluoro-deoxyglucose or FDG which
becomes trapped in the cancer cells, heart muscle, or
brain cells. |
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2. |
The PET Scanner records the signals the
tracers emit as it collects in the tissues targeted for
examination. |
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3. |
A computer then reconstructs
these signals into actual images which reveal information
about the biochemical metabolism within the patient. (Shows
up as hot spots on the scan). |
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What is PET used for? |
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Cancer/Tumors |
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PET imaging has proved to be very accurate in showing the
presence and also the spread of malignant tumors. In the
body, all cells use glucose. But in cancer cells,
glucose is metabolized (used up) at a much higher rate
than normal body cells. The PET scan will pick up this
metabolic anomaly and show it as a “hot” spot on the film
(see case studies section). |
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PET is the most accurate means of detecting the spread of
lung, colon, prostate, head & neck, and breast cancer than
any other imaging methods. In addition it is used to detect
melanoma, lymphoma, and various other tumors. Once the
diagnosis has been made, this information can be used to
determine what possible treatment is best for the patient.
In some cases, PET scans eliminated the need to commence
with treatment since it determined that cancer was not
present in the patient at all. |
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2. |
Cardiology |
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The radioactive glucose
tracer has a unique ability to determine whether or not the heart
muscle can recover following a heart attack
(myocardial viability). This
information is used to predict the outcome of coronary
artery bypass surgery, angioplasty, or other procedures to select which patients would most likely benefit from
these procedures (see case study #11). |
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Brain/Neurology |
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PET imaging of the
brain using radioactive glucose can be used to determine
whether a patient is developing Alzheimer’s disease, or
other diseases that can cause memory loss or mental
deterioration. Some patients who suffer epileptic seizures
and do not respond well to drug therapy may benefit from
surgery. PET can help determine the exact brain region
that is causing the seizures, and determine if it can be
removed to relieve the seizures. After going into
remission, brain cancer can reoccur and are best detected
with PET (see case study #3). |
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What can a PET Scan tell me about cancer? |
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1. |
Determine whether the lump or nodule is
benign or malignant |
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Because cancer cells are
highly metabolic and use more glucose than normal cells,
PET scans are able to identify whether or not a suspicious
lump is benign or cancerous. |
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Has the cancer spread |
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PET scans
can determine if the cancer has spread to the body's
filters (lymph nodes), other organs, and bones.
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Assessment of Cancer Treatment |
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Because PET
scans have the ability to identify cancerous cells, it is
also a valuable tool in determining whether or not the
current treatment being used is effective or not. A before
and after PET scan of a patient who underwent treatment
(like chemotherapy for example), will be able to determine
if the treatment was effective in stopping the cancer or
whether a new course of treatment needs to be initiated. |
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4. |
Reoccurrence of Cancer |
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PET can be
used if a suspected reoccurrence of cancer is in
question and needs to be determined. |
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