Used mostly in patients with brain or heart conditions and cancer, PET helps to visualize the biochemical changes taking place in the body, such as the metabolism the process by which cells change food into energy after food is digested and absorbed into the blood of the heart muscle.
PET differs from other nuclear medicine examinations in that PET detects metabolism within body tissues, whereas other types of nuclear medicine examinations detect the amount of a radioactive substance collected in body tissue in a certain location to examine the tissue's function. Since PET is a type of nuclear medicine procedure, this means that a tiny amount of a radioactive substance, called a radiopharmaceutical radionuclide or radioactive tracer , is used during the procedure to assist in the examination of the tissue under study.
Specifically, PET studies evaluate the metabolism of a particular organ or tissue, so that information about the physiology functionality and anatomy structure of the organ or tissue is evaluated, as well as its biochemical properties.
Thus, PET may detect biochemical changes in an organ or tissue that can identify the onset of a disease process before anatomical changes related to the disease can be seen with other imaging processes such as computed tomography CT or magnetic resonance imaging MRI.
PET is most often used by oncologists doctors specializing in cancer treatment , neurologists and neurosurgeons doctors specializing in treatment and surgery of the brain and nervous system , and cardiologists doctors specializing in the treatment of the heart. However, as advances in PET technologies continue, this procedure is beginning to be used more widely in other areas.
PET may also be used in conjunction with other diagnostic tests, such as computed tomography CT or magnetic resonance imaging MRI to provide more definitive information about malignant cancerous tumors and other lesions. Originally, PET procedures were performed in dedicated PET centers, because the equipment to make the radiopharmaceuticals, including a cyclotron and a radiochemistry lab, had to be available, in addition to the PET scanner.
Now, the radiopharmaceuticals are produced in many areas and are sent to PET centers, so that only the scanner is required to perform a PET scan. Further increasing the availability of PET imaging is a technology called gamma camera systems devices used to scan patients who have been injected with small amounts of radionuclides and currently in use with other nuclear medicine procedures.
These systems have been adapted for use in PET scan procedures. The gamma camera system can complete a scan more quickly, and at less cost, than a traditional PET scan. PET works by using a scanning device a machine with a large hole at its center to detect photons subatomic particles emitted by a radionuclide in the organ or tissue being examined.
The radionuclides used in PET scans are made by attaching a radioactive atom to chemical substances that are used naturally by the particular organ or tissue during its metabolic process.
For example, in PET scans of the brain, a radioactive atom is applied to glucose blood sugar to create a radionuclide called fluorodeoxyglucose FDG , because the brain uses glucose for its metabolism.
From start to finish, the procedure takes about two hours to complete and typically does not require an overnight hospital stay. When you arrive for your scan, you may be asked to:. A member of your health care team injects the radioactive drug tracer into a vein in your arm or hand.
You may briefly feel a cold sensation moving up your arm. You rest and remain silent in a reclining chair for 30 to 60 minutes while the tracer is absorbed by your body. When you are ready, you lie on a narrow, padded table that slides into the part of the scanner that looks like a doughnut hole.
During the scan you must be very still so that the images aren't blurred. The machine makes buzzing and clicking sounds. The test is painless. If you're afraid of enclosed spaces, you may feel some anxiety while in the scanner. Be sure to tell the nurse or technologist about any anxiety causing you discomfort. He or she may give you a drug to help you relax. After the test you can carry on with your day as usual, unless your doctor tells you otherwise.
You'll need to drink plenty of fluids to help flush the tracer from your body. A doctor specially trained to interpret scan images radiologist will report the findings to your doctor. Or the PET images may be combined to provide more detail about your condition. Explore Mayo Clinic studies of tests and procedures to help prevent, detect, treat or manage conditions.
Positron emission tomography scan care at Mayo Clinic. It is safe to use during pregnancy and is also a…. Radiation is a type of energy that travels from one place to another. While high levels can be dangerous for people after exposure, low levels are…. What is a PET scan, and are there risks? Medically reviewed by Judith Marcin, M. How it works Uses Procedure Risks A positron emission tomography, also known as a PET scan, uses radiation to show activity within the body on a cellular level.
How it works. Share on Pinterest PET scans demonstrate the physical state and function of organs. Share on Pinterest PET scans are an important part of the diagnostic process in cancer and epilepsy, and can directly inform the next stage of treatment. Latest news Could 'cupping' technique boost vaccine delivery? Scientists identify new cause of vascular injury in type 2 diabetes.
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Medically reviewed by Dr. Payal Kohli, M. You have an injection of radiotracer about an hour before the scan. You have the injection through a small plastic tube in your arm cannula. It's only a small amount of radiation. You need to rest and avoid moving too much during this hour. This allows the radiotracer to spread through your body and into your tissues. The radiotracer is a radioactive sugar.
The one commonly used is called FDG fluorodeoxyglucose. Cancer cells are very active when they are growing and reproducing in a specific area. They need energy to grow. So, active cancer cells take up the FDG which then shows up brighter on the scan. Your radiographer takes you into the scanning room. The PET machine is large and shaped like a doughnut. They can see you on a TV screen or through a window from the control room.
You can talk to each other through an intercom. The couch slowly slides backwards and forwards through the scanner. The machine takes pictures as you move through it. The scan is painless but can be uncomfortable because you have to stay still. In most places the radiographer will be able to play music for you.
They can also help your doctor decide which treatment you need and whether your treatment is working. Voiceover : For some scans you should not eat for 4 to 6 hours beforehand, for others there is no preparation.
Your appointment card will give you details of what you need to do. One you have changed into your gown the radiographer will weigh and measure you. Then you have an injection of a very small amount of a radioactive drug called a tracer. This is what shows up on the scan. The drug is usually a form of glucose. Voiceover : After the injection you rest for about an hour. This allows the tracer to spread through your body.
The scan shows up cancer because they use glucose in a different way from normal tissue. When you are ready for the scan the radiographer helps you lie on the couch in the correct position.
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