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Metabolic data
The metabolic data that describes the bio-chemical functioning (uptake of nutrients,
etc) of the tumour is captured using the Positron Emission Tomography (PET)
scanner inside the PET/CT machine. The way it captures the images is explained
below:
The PET scans give information about the body's chemistry that is not available
with other imaging techniques, revealing metabolic information providing the
physician with extra insight.
The Positron Emission Tomography procedure works like a camera that produces
detailed images of biological functions from inside the human body.
The Positron Emission Tomography scan is a unique, non-invasive diagnostic
imaging tool that is a metabolic imaging tool. What this means is that a PET
scan produces images detailing the biochemical functioning of an organ or tissue.
In essence The PET scan visualizes biochemical changes caused by disease.
- In the PET scan procedure, a patient is given a substance that is tagged
with a radiopharmaceutical. The radiopharmaceutical contains a radioactive
that is used to help visualize metabolic changes in the body.
- This radioactive isotope is not dangerous to the person who take it as it
has a short half-life, meaning that the radiation only last for a very short
period of time, before which the isotope decays to become a stable element.
The period is so brief that the radiation does no damage to the body, but
can be used in helping to locate tumours
- Radio pharmaceuticals are given to a patient predominantly through an injection,
but can also be given through an existing intravenous line or inhaled as a
gas. The injection is usually given an hour before the scan to allow the tracer
to move through the body and also allow uptake in the areas under investigation.
- The most common injection used in a PET scan is FDG. FDG is short for Fluorodeoxyglucose,
a glucose-based radio pharmaceutical of Fluoride 18.
- In the scan the patient lies flat on a bed or table that moves steadily
through the PET scanner.
- As FDG decays it emits protons (positively charged atoms). These positive
protons collide with electrons (negatively charged atoms) from the scanner
to produce gamma rays.
- The PET scanner has cameras that detect the gamma rays emitted from the
patient, and turns these emissions into electrical signals.
- A computer generates the medical images by processing the gamma ray signals
that are collected by the scanner.
- If an area is cancerous, the signals will be stronger there than in surrounding
tissue as more of the radio pharmaceutical (FDG) is being absorbed in those
areas, due to cancerous tumours absorbing more glucose than non-cancerous
areas.
- This finite procedure produces clear digital images, which are assembled
by the computer into a 3-D image of the patient's body. In the PET/CT scanner
the images from the PET are combined with the CT scan results to gather more
detailed information on the tumour
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