An integrated PET-CT scan combines the images from a positron emission tomography (PET) scan and a computed tomography (CT) scan, performed at the same time. Together, the two scans create a more complete image than either test can offer alone.
An integrated PET-CT scan is a diagnostic examination used to detect and determine the stage (a measurement given or a diagnosis that describes the size of the original tumor and identifies whether the tumor has spread to lymph nodes or other parts of the body) of cancer, determine whether cancerous cells have spread, and evaluate the effectiveness of cancer treatments. The scan is also used to guide some types of biopsies (the removal of a small amount of tissue for examination by a pathologist).
About The Scans
In a PET scan, radioactive sugar molecules are injected into the body. Cancer cells absorb sugar more quickly than normal cells, so they "light up" on the images created by the PET scanner. The scan shows the activity within the cells, tissues, and organs.
The CT scanner takes a series of x-ray pictures, which are combined by a computer to create an extremely detailed image including anatomical data such as the size, shape, and location of an organ or tumor. Generally, the scan includes nearly the entire body.
The Medical Team
An integrated PET-CT is performed by a radiologist or radiology technologist, who specializes in CT scanning and nuclear medicine. A radiologist is a medical doctor who performs and interprets imaging tests to diagnose disease. A radiology technologist is specially trained and certified to operate PET-CT scanners.
Immediately prior to the scan, a nurse will give you the injection or intravenous (IV) line for the test. The IV always includes the radioactive sugar and sometimes will include a contrast material that contains iodine.
Preparing For The Procedure
When you schedule the examination, you will get detailed instructions on how to prepare. Tell your doctor about all the medications you are taking, and review with him or her whether you should take your regular medications that day.
Review any drug allergies or other medical conditions you have, especially any allergic reactions you've had to iodine or shellfish.
Women should tell their doctors if they are breast-feeding or if there is any chance that they are pregnant.
You may be told to drink only clear liquids starting at midnight the night before your exam. You may be instructed to not eat or drink anything for at least four hours prior to your scan.
You may want to ask if you can bring your own music. Some facilities allow patients to listen to music during their examinations.
You will be asked to sign a consent form that states you understand the benefits and risks of the PET-CT scan and agree to have the test done. Talk with your doctor about any concerns you have about the scan.
During The Procedure
When you arrive, you may need to change into a hospital gown or remove clothing or jewelry that could interfere with the scan such as belts, earrings, shirts with snaps or zippers, bras, and glasses.
A nurse will then inject the radioactive sugar molecules needed for the PET scan. The injection is often done through an IV line inserted in your vein. The IV line will feel like a pinprick when it is inserted, but the radioactive material will not create any sensation in your body. It takes the sugar about 30 - 90 minutes to reach the tissues. During that time, you will need to lie quietly without moving or talking (too much motion can affect the sites where the sugar molecules accumulate)...
You may also be given a contrast agent (dye) for the CT. It may be a drink or an injection. The dye travels through your blood and helps to create a clearer picture.
If you get the dye through an injection, you may feel heat or itching at the site or get a metallic taste in your mouth; both should disappear in a few minutes. If you have a more severe reaction, tell the technologist immediately.
When it's time for the examination to begin, the technologist will help position you on a padded exam table outside the scanner. The table may have straps or pillows to help hold you in place or a special cradle for your head. You will probably lie on your back, although you may be asked to lie on your side or your stomach.
During the scan, the technologist will be monitoring you from an adjoining control room and will be able to observe you through a window or by means of a video camera. You will be able to communicate through an intercom system.
The PET-CT scanner resembles a large donut. The exam table will slide back and forth through the large hole in the center of the machine as the scanner rotates around you. For the first scans, the table will move rapidly through the scanner; these help the technologist confirm that your body is properly positioned. For the remaining scans, the table will move more slowly. The CT scans are done first, and then the PET scans.
A PET-CT scan is not painful. You will need to lie still for the entire scan, and you may need to keep your arms raised above your head, which could become uncomfortable. The PET-CT scanner needs to be kept cool, so the examination room may feel chilly.
You will hear whirring or clicking sounds from the machine; some machines are noisier than others. You may be asked to hold your breath during part of the scan because the motion created by breathing can blur the images. The exam table may be raised, lowered, or tilted to create the correct angle for the scan; ask the technologist performing the scan to tell you when the table will move.
The exam will last up to an hour, though the scanning itself takes only about 30 minutes. If a larger part of your body is being scanned, the procedure may last longer.
When the scan is finished, you may be asked to remain on the exam table while a radiologist reviews the images. If the images are blurred or otherwise unreadable, you may need to have additional images taken.
After The Procedure
You can expect to resume your normal activities immediately after your PET-CT scan, including driving. You may be advised to drink water to help flush the contrast material and radioactive sugar out of your body