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A PET (Positron Emission Tomography) scan is an imaging test that uses a special camera and a radioactive substance (tracer) to look at the organs in the body. The tracer is usually a substance like glucose which can be metabolized by the cells in the body.
The tracer is injected into a vein, travels through the bloodstream, and collects in organs. This process can take about 30-60 minutes. During this time, the person may be asked to avoid moving or talking. Then, the person will lie on a table that slides into the PET scanner. The tracer gives off positrons (tiny positively charged particles) which the camera will record and turn into 3-dimensional pictures on a computer screen. During this time, the person will be instructed to lie very still.
The entire test can take 1-3 hours.
What is a PET scan used for?
A PET scan is used to check blood flow, see how well organs are working, and find problems. Benefits of having a PET scan include:
• Diagnosing cancer (early stages may be clearer using a PET scan than a CT scan or MRI). It can show how advanced the cancer is and if it has metastasized (spread) to other parts of the body.
• Diagnosing heart problems such as poor blood flow to the heart and how much damage has occurred after a heart attack.
• Diagnosing brain disorders and nervous system problems such as epilepsy, stroke, Alzheimer's disease, multiple sclerosis, Parkinson's disease, Huntington's disease, and schizophrenia.
Besides finding problems, the PET scan can help the doctor choose the most appropriate treatment and monitor the progress of treatment.
What is required before a PET scan?
• The person will be told to not eat or drink anything before the test (usually 6 hours). Water may be allowed.
• The person will most likely be told to not smoke or consume alcohol or caffeine 24 hours prior to the test.
• People taking medications (including prescription and over-the-counter) or herbal remedies may be instructed to stop taking (or change the dose) before the test.
Although the amount of radiation is low, women who are pregnant should not have a PET scan done unless it is absolutely necessary (a woman who thinks she may be pregnant should let her doctor know).
What is expected after the PET scan?
The person will be told to drink a lot of fluids (preferably water) for 24 hours. This will help flush the tracer from the body.
Women who are breastfeeding will be told to bottle feed for 1-2 days after the PET scan so the tracer will not pass on to the baby. Women can prepare for this by pumping and saving breast milk.
It can take up to 1-2 business days to get complete results of the test.
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Image courtesy of NASA (in the public domain).