PET stands for “positron emission tomography”. It is a nuclear medicine imaging test in which a small amount of liquid radioactive material is injected into the body and is used to diagnose a variety of diseases, including many types of cancers, and brain and heart disease.
The radioactive substance most commonly used in PET scanning is a simple sugar (like glucose) called FDG, which stands for “fluorodeoxyglucose”. It is injected into the bloodstream and accumulates in the body where it gives off energy in the form of gamma rays. These are detected by the PET scanner and a computer converts the signals into detailed pictures or images showing how tissue and organs are working. If you are having an FDG-PET, your sugar metabolism (how sugar is used by your body) is imaged. This is commonly used for cancer imaging, as the cancer cells need sugar to grow. FDG is also useful for imaging inflammatory or infective processes, and for imaging brain metabolism.
PET scanners are combined with computed tomography (CT) scanners, called PET-CT scanners. CT imaging uses X-ray equipment to create detailed images of slices of the inside of your body. The PET-CT combination allows any abnormality on the PET scan to be precisely located within the body, allowing for more accurate diagnosis of any problems. The PET or PET-CT scanner looks like a large box with a circular hole in the middle.
The reasons for having a PET-CT scan are continually evolving, with new ways of testing a broader range of conditions and symptoms, and using new radioactive substances. Nevertheless, most PET scans are carried out in patients with cancer. PET-CT is important for identifying certain cancers and assessing their spread through the body. This will allow your doctor to determine the most appropriate treatment for you and advise you on your options. Scans are also used at intervals to determine whether the cancers have responded to your treatment.
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