What is a Positron Emission Tomography exam?
Positron emission tomography (PET) is a nuclear medicine procedure that produces pictures of the body’s biological functions.  PET is a unique diagnostic imaging modality that is capable of detecting certain diseases before other imaging modalities such as: computed tomography (CT) and magnetic resonance imaging (MRI).  PET is able to capture chemical and physiological changes related to metabolism, as opposed to gross anatomy and structure, which is obtained by CT and MRI.  This is important since functional changes are often present before structural changes in tissues.  PET images may therefore demonstrate pathological changes long before they would be evident in CT or MRI.  PET/CT is valuable because it combines the pathological information with the anatomical giving your doctor a large amount of information to make the most informed decision.

What are some common uses for PET?
PET scans are most often used to detect cancer and to examine the effects of cancer therapy.  These scans can be performed on the entire body for a range of cancer types.  PET scans of the heart can be used to help evaluate signs of coronary artery disease by determining blood flow to the heart muscle.  It allows differentiation of nonfunctioning heart muscle from heart muscle that would benefit from a procedure which would re-establish adequate blood flow and improve heart function.  PET scans of the brain are used to evaluate patients who have memory disorder of an undetermined cause.

How do I prepare for a PET scan?
Your physician will advise on eating or drinking prior to your exam, but typically, you will be asked not to eat or drink anything besides water for four to six hours prior the exam.  During the exam itself, you should wear comfortable clothes and take any prescribed medications on the day of the exam unless instructed not to do so by your physician.  Diabetic patients should ask about specific diet guidelines to control glucose levels during the day of the test.

What can I expect during the PET scan?
Before the scan, you will be injected with a radioactive tracer.  The tracer is a compound such as glucose, labeled with a short-lived radioisotope.  Once injected, you will be asked to rest for approximately thirty to forty-five minutes while the radioactive compound distributes throughout your body, and is processed by the organs being evaluated.  Different colors or degrees of brightness on a PET image represent different levels of tissue or organ funciton.  For example, because healthy tissue uses glucose for energy, it accumulates some of the tagged glucose, which will show up on the PET images.  However, cancerous tissue, which uses more glucose than normal tissue, will accumulate more of the substance and appear brighter than normal tissue on the PET images.  The radiation exposure associated with PET is safe and much lower than that associated with conventional CT scanning.  The technologist will ask you to lie on the scanner table, which will then slowly pass through the PET scanner.  The PET scanner detects and records the signals the tracers emit. The signals are then reassembled into actual images through a computer.

How long will my PET scan take?
Every PET exam is different, but most patients can expect to be at the hospital or imaging center for at least two hours.  This includes the time needed for the injected tracer to distribute throughout your body, as well as the time you actually spend moving through the PET scanner.  The exact length of your exam will be determined by the type of study being performed.

What will happen following my PET scan?
You should feel fine following your PET scan.  There are no known side effects from the injected tracer.

How do I find out the results of my PET scan?
Your PET scan will be reviewed by a Radiologist or nuclear medicine physician.  The radiologist or nuclear medicine physician will send a report to your physician, who will give you the results of the scan.  It usually takes one to three days to interpret, report and deliver the results.  In order to facilitate interpretations, you may be asked to bring any previous radiologic images with you, such as recent CT or MRI images.

Learn more at http://www.petforcancer.com/ and www.radiologyinfo.org