The PET/CT fusion scan
produces a series of images and can detect many conditions that do not show up on conventional x-rays or nuclear medicine scan. PET-CT scan consists of 2 parts – CT scan for attenuation correction and localization and PET scan. During the CT scan, a thin beam of x-rays is focused on a specific part of your body, such as the head, chest, liver, spleen, pancreas, adrenal glands, kidneys, or spine. The x-ray tube moves rapidly around this site, enabling multiple images to be made from different angles to create cross-sectional picture. The x-ray beam is picked up by an electronic detector which records the information and feeds it into a computer. During a PET scan, a ring of detectors picks up radiation signals from the patient’s body coming from previously injected radiopharmaceuticals. The computer then analyzes the information and constructs an image on a monitor screen including a volume display of your organ.
>> Who is a candidate for the test?
Your PET exam results may have a major impact on your physician's diagnosis of a potential health problem - and, should a disease be detected, how your return to health is managed. A PET study not only helps your physician diagnose a problem; it also helps your physician predict the likely outcome of various therapeutic alternatives, pinpoint the best approach to treatment, and monitor your progress. If you're not responding as well as expected, you can be switched to a more effective therapy immediately. Just ask your physician what he or she hopes to learn from your PET exam.
>> Who performs the test?
Although your personal physician requests the PET/CT scan, a radiologist and/or nuclear physician or technician/radiographer performs the actual procedure. The radiologists/nuclear physicians are medical doctors who specialize in the use of imaging for diagnosis of medical conditions. The doctors are assisted by a radiology technologist, a person who has extensive training in the use of diagnostic imaging equipment. Together, these highly skilled professionals will make sure that your PET/CT scan pictures are of the best quality possible and that you are as comfortable as possible throughout the procedure.
>> How long does it take?
Your exam will vary depending on what your physician is looking for, and what is discovered along the way. Expect to spend 2 to 3 hours getting your PET exam.
>> What you can do to help make it a success?
A PET/CT scan is usually painless. The machine does not touch you and you do not feel the x-rays.Occasionally, some patients are administered a contrast medium. This may be given orally or by injection e.g. an intravenous injection. In some patients, the actual injection can be associated with a sensation of warmth, heat or flushing. These feelings are transient and will typically resolve spontaneously. This rarely occurs today because newer, safer products called nonionic contrast media have been developed, and they reduce most discomfort. You can help assure a successful, comfortable procedure by carefully following the instructions of your physician, the radiologist, and the radiology technologist. Be sure to answer carefully any questions they may ask about your general health. For example, tell them if you are pregnant, diabetic, and/or allergic to any foods or drugs. Let them know if you have had any contrast media in the past and if you had any side effects. Give them a complete list of any medications you may be taking now, including nonprescription medications. Also indicate if you have had or are presently being treated for an infection in any part of your body.
>> What to do before your exam?
This guide provides a step-by-step description of what to expect before, during, and after your PET/CT scan. But please remember that it is only a guide. Some steps may vary depending on your condition, the personal preferences of your physician, and the standard procedures of the hospital or center where the test is performed. As with other important diagnostic procedures, you may be asked to sign an informed consent to undergo a PET/CT scan. That is your opportunity to ask any questions following a description of the risks, benefits, and alternatives of the procedure. The contents of this guide are for your information only and are not to be interpreted as taking the place of informed consent. Do not hesitate to discuss your upcoming PET/CT exam with your physician or the radiologist.
Following are a few steps that your doctor may ask you to take before you go to the hospital or PET/CT center for your exam. These same general steps may be recommended if you are a hospitalized patient.
It depends of type of radiopharmaceutical which will be used during your PET/CT scan, your doctor will probably ask you not to eat anything for four to six hours or more before the exam. In addition, you may be asked not to drink anything for one hour before the exam.
If you are having a body scan, you will probably be asked to undress and put on a hospital gown for the exam. You will also be asked to remove any jewelry or metallic properties such as keys so that it does not interfere with the x-ray imaging.
If you are having a PET/CT scan of your head, you may be asked to wear loose, comfortable clothing for the exam. And you will need to remove dentures, glasses, hearing aids, earrings, hairpins, and any other objects that may be in the path of the x-ray beam.
>> What happens during your exam?
After reviewing your history and any prior exam, you'll receive a radiopharmaceutical injection. This is a radioactive tracer that must pass multiple quality control measures before it is used for any patient injection. For most studies, you'll have to wait for the radiopharmaceutical to distribute itself - in Europe is always 1h minimum and 1h30 maximum. You may be able to read or listen to music until your scan begins - and perhaps during the scan itself. However, if your brain is being scanned, you will be asked to wait in a quiet, dimly lit room, without stimulating your brain by reading or talking. If you're having a heart study, on the other hand, you may not have to wait at all; the radiopharmaceuticals used for cardiac exams are often administered just before scanning begins.
When you're ready for scanning, you'll lie on a comfortable table that moves slowly through the ring-like PET scanner as it acquires the information it needs to generate diagnostic images. You will be asked to lie very still, because movement can interfere with the results. You shouldn't feel a thing during the scan, which can last anywhere from 30 to 45 minutes. Then, unless the physician sees a need for acquiring additional information, you will be free to leave.
>> What to do after your exam?
You may leave as soon as the scan is complete. Unless you've received special instructions, you'll be able to eat and drink immediately - drinking lots of fluids will help remove any of the radiopharmaceutical that may still be in your system. In the meantime, your results will be prepared for review and the findings forwarded to your physician, who will tell you what has been learned.
>> Are There Risks Associated With This Exam?
A PET, PET/CT study is similar to many other diagnostic procedures, from CT and MRI to Nuclear Medicine.
Radiopharmaceuticals used in PET don't remain in your system long, so there's no reason to avoid interacting with other people once you've left. To be extra safe, wait for a few hours before getting too close to an infant, or anyone who's pregnant. Please consult your physician with any additional questions or concerns.