PET (positron emission tomography) scanning is an imaging technique that uses a radioactive tracer that is injected into the patient. Images of the body are produced, and degrees of brightness represent different levels of tissue or organ metabolism (chemical reactions that occur in cells).
The substance injected into the patient is glucose (sugar) that has a radioactive material tagged to it. Areas of the body that use a lot of glucose, such as the brain and heart, will pick up this radioactive material and appear hot. Abnormal cells in the body that use a lot of glucose will also appear as "hot spots." Cancer cells are highly metabolic and use a lot of sugar. That's why this test is useful in aiding in diagnosing and staging cancer.
PET scans do not diagnose cancer; they only show areas of abnormal uptake of the tracer material. Other diseases can produce "hot spots," such as infection.
In addition, false-positives (test results that are erroneously classified in a positive category) or false-negatives (test results that are erroneously classified in a negative category) can exist if a patient ate within a few hours of the test, or if the patient is a diabetic. Slow-growing cancers are hard to detect on PET, as well as cancers that are smaller than half an inch in size.
PET scans are helpful in guiding the physician when a cancer is suspected. It can assist in the staging of a cancer, which is very important in determining the treatment plan. PET scans are also used to help the doctor determine whether a treatment is effective.
The radioactive material used is short-lived and radiation exposure is low. It is a non-invasive test. The radioactive material will be injected, and you will be asked to wait for about an hour; then your scan will be done. The scan can also take up to 1 hour to complete, depending on which parts of the body are being examined.
The entire process for this test can take about 2 hours. You will be asked to lie still while the pictures are taken. The machine has a padded table on which you lie, and this table slides into a large, doughnut-shaped hole in the middle of the machine.
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