Positron Emission Tomography (PET) Scan

What is a PET Scan?
A positron emission tomography (PET) scan is a safe, effective and painless molecular imaging exam that is used to detect the presence and extent of cancer, cardiovascular disease, neurological conditions and other physiological problems.

While other imaging techniques—such as X-rays or CT scans—provide anatomical information about the way organs or tissues look, a PET scan shows what the cells in those organs or tissues are doing. That functional information is then used for diagnosis, evaluation and treatment of disease.


How Does a PET Scan Work?
A PET scan uses very small amounts of radioactive isotopes (tracers) that are targeted to specific molecules, organs or tissues by attaching them to other compounds such as glucose. The resulting radiopharmaceutical is then administered to the patient and detected or "traced" with a special type of camera to provide precise pictures of the area of the body being imaged.

Because a PET scan is noninvasive and does not involve the risks of surgery, it can be performed repeatedly, if necessary, with minimal risk.

Most individuals undergo PET scans as outpatients. During the scan, the patient is asked to lie still while the PET camera images the distribution of radiotracer in his or her body. The very small amount of tracer administered usually remains in the body for only a short period of time; there are no known adverse effects from such low doses.

During the imaging process, patients are cared for by nuclear medicine technologists. Technologists and other specialists work with sophisticated imaging devices, computers and assessment techniques.

After the PET scan, a nuclear medicine physician reviews the images, prepares a written report and may discuss the results with the patient's doctor.

Why Is a PET Scan Important?
A PET scan is an integral part of the diagnosis, management, and treatment of serious disease. A single PET scan can provide information that once would have required many medical studies, and it can do so without the surgery or other invasive procedures that might otherwise have been required.

PET scans often reveal disease before it can be seen with other tests. Often, in addition to imaging the disease, it can provide information used to determine the most promising treatment methods. PET scans are also used to evaluate how well treatments are working and can often show significant changes far sooner than other tests.

PET Applications
A PET scan provides state-of-the-art imaging and valuable clinical information in:

  • Cancer diagnosis (breast, cervical, colorectal, esophageal, head and neck, lung, lymphoma, melanoma, pancreatic, thyroid and others)
  • Evaluation of cancer therapy
  • Diagnosis of cardiovascular disease; evaluation of potential effectiveness of therapy
  • Alzheimer's disease, Parkinson's disease, dementia, epilepsy and other neurological diseases

PET and Cancer
The fastest-growing area of PET scanning has been in oncology. PET imaging can reveal the location of tumors or other lesions and provide information about the extent of disease, benign or malignant status, and possible spread. A PET scan may help avoid surgical biopsy or find a site that is easier to biopsy.

A PET scan is considered to be the most accurate diagnostic procedure for assessing whether many types of cancer have recurred after treatment. It is also effective in evaluating the potential success of specific therapies.

PET and Heart Disease
A PET scan can accurately detect coronary artery disease, allowing physicians to identify areas of decreased blood flow and distinguish damaged from healthy heart tissue. This information is especially important for individuals who have had previous heart attacks and are being considered for additional procedures.

PET and Alzheimer's and other Brain Disorders
The PET scan has expanded our ability to diagnose and evaluate Alzheimer's disease, seizure disorders and other neurological conditions. 'The unique metabolic imaging ability of PET can help pinpoint the initially small variations from normal brain activity that occur due to Alzheimer's disease—a diagnosis that previously could be made only at autopsy. Early diagnosis of neurological disorders opens up a range of treatment options. The ability of PET to measure the success of these treatments is central to current cutting-edge research in the management—and even prevention—of some disorders.

PET and the Future
Nuclear medicine researchers are investigating new radiotracers and new PET applications that may reveal disease processes that have never before been imaged.

PET is now being combined with other imaging techniques—such as computed tomography (CT)—to create "fusion" images that provide an anatomical context to the functional information.

In 2005, an estimated 1,129,900 clinical PET scan patient studies were performed using PET or PET/CT scanners or nuclear medicine cameras in 1,725 hospital and non-hospital sites in the United States. According to a report by IMV Medical Information Division, the number of patient studies increased more than 60 percent since 2003, for an average annual growth rate of 26.5 percent over the two-year period.

The PET scan—alone and in combination with other techniques—will continue to provide a unique look into the body and yield valuable information for therapy and preventive health measures.

SNM—with its 16,000 physician, technologist and scientist members—promotes the science, technology and practical application of molecular imaging and therapy for the diagnosis and treatment of diseases. SNM has taken the lead in the science of PET through research, education and training of its members. Visit SNM's PET Center of Excellence for more information about how the center works with members to advance the science of PET.