A positron emission tomography (PET) scan is an imaging test that helps reveal how your tissues and organs are functioning. A PET scan uses a radioactive drug (tracer) to show this activity.

The tracer may be injected, swallowed or inhaled, depending on which organ or tissue is being studied by the PET scan. The tracer collects in areas of your body that have higher levels of chemical activity, which often correspond to areas of disease. On a PET scan, these areas show up as bright spots.

A PET scan is useful in revealing or evaluating several conditions, including some cancers, heart disease and brain disorders.

A PET scan is an effective way to examine the chemical activity in parts of your body. It may help identify a variety of conditions, including some cancers, heart disease and brain disorders. The pictures from a PET scan provide information different from that uncovered by other types of scans, such as computerized tomography (CT) or magnetic resonance imaging (MRI). A PET scan or a combined CT-PET scan enables your doctor to better diagnose your condition.

Cancer

Cancer cells show up as bright spots on PET scans because they have a higher metabolic rate than do normal cells. PET scans may be useful in:

  • Detecting cancer
  • Revealing whether your cancer has spread
  • Checking whether a cancer treatment is working
  • Finding a cancer recurrence

PET scans must be interpreted carefully because noncancerous conditions can look like cancer, and many types of cancer do not appear on PET scans. The types of cancer most likely to show up on PET scans include:

  • Brain
  • Breast
  • Cervical
  • Colorectal
  • Esophageal
  • Head and neck
  • Lung
  • Lymphoma
  • Melanoma
  • Pancreatic
  • Prostate
  • Thyroid

Heart disease

PET scans can reveal areas of decreased blood flow in the heart. This information can help you and your doctor decide, for example, whether you might benefit from a procedure to open clogged heart arteries (angioplasty) or coronary artery bypass surgery.

Brain disorders

PET scans can be used to evaluate certain brain disorders, such as:

  • Tumors
  • Alzheimer's disease
  • Seizures

For your PET scan, a radioactive drug (tracer) will be put into your body. The amount of radiation you're exposed to is small, and the risk of negative effects from it is low. But the tracer might:

  • Cause a major allergic reaction, in rare instances
  • Expose your unborn baby to radiation if you are pregnant
  • Expose your child to radiation if you are breast-feeding

Talk with your doctor about the benefits and risks of a PET scan.

Tell your doctor:

  • If you've ever had a bad allergic reaction
  • If you've been sick recently or you have another medical condition, such as diabetes
  • If you're taking any medications, vitamins or herbal supplements
  • If you're pregnant or think you might be pregnant
  • If you're breast-feeding
  • If you're afraid of enclosed spaces (claustrophobic)

Your doctor will give you detailed instructions on how to prepare for your scan. A general rule is to avoid strenuous exercise for a couple of days before the study and to stop eating a few hours before the scan.

The PET scanner is a large machine that looks a little like a giant doughnut standing upright, similar to a computerized tomography (CT) machine. You'll need about two hours for the procedure, which may be done on an outpatient basis (no overnight hospital stay). When you arrive for your scan, you may be asked to:

  • Change into a hospital gown
  • Empty your bladder

Then you will be given a radioactive drug (tracer). You may receive the drug by injection or be asked to inhale or swallow it, depending on the type of tracer being used. If the drug is injected, you may briefly feel a cold sensation moving up your arm. You'll need to wait 30 to 60 minutes for the tracer to be absorbed by your body.

During the PET scan

When you are ready, you'll lie on a narrow, padded table that slides into the scanner. During the scan you'll need to lie very still so that the images aren't blurred. It takes about 30 minutes to complete the test. 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 discomfort. He or she may give you a drug to help you relax.

In some cases you may have a CT and PET scan in the same machine during the same appointment. The CT scan will be done first and take about 10 minutes.

After the PET scan

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.

Pictures from a PET scan display bright spots where the radioactive tracer collected. These spots reveal higher levels of chemical activity and details about how your tissues and organs are functioning. A doctor specially trained to interpret scan images (radiologist) will report the findings to your doctor.

The radiologist may also compare your PET images with images from other tests you've undergone recently, such as computerized tomography (CT) or magnetic resonance imaging (MRI). Or the pictures may be combined to provide more detail about your condition.

  • Experience. Specially trained radiologists at Mayo Clinic perform and interpret the results of more than 11,000 PET scans annually.
  • Technology. Mayo Clinic campuses in Arizona, Florida and Minnesota have state-of-the-art PET scanners. In Minnesota, Florida and Arizona, some PET machines are combined with a CT scanner to enhance imaging results.
  • Integrated team approach. Mayo Clinic radiologists work with your doctor to help develop the most appropriate treatment plan for you.
  • Innovation. Mayo Clinic was the first institution approved by the Food and Drug Administration to produce an imaging agent (choline C-11) that helps detect recurrences of prostate cancer. Mayo Clinic uses this agent during PET scans.

Read more about choline C-11 PET scan.

Mayo Clinic works with hundreds of insurance companies and is an in-network provider for millions of people. In most cases, Mayo Clinic doesn't require a physician referral. Some insurers require referrals or may have additional requirements for certain medical care. All appointments are prioritized on the basis of medical need.

Doctors in the Department of Radiology at Mayo Clinic in Arizona use a PET scanner that is combined with a CT scanner.

For appointments or more information, call the Central Appointment Office at 800-446-2279 (toll-free) 8 a.m. to 5 p.m. Mountain Standard Time, Monday through Friday or complete an online appointment request form.

Doctors in the Department of Radiology at Mayo Clinic in Florida have been performing positron emission tomography since 1997.

For appointments or more information, call the Central Appointment Office at 904-953-0853 8 a.m. to 5 p.m. Eastern time, Monday through Friday or complete an online appointment request form.

Doctors in the Department of Radiology at Mayo Clinic in Minnesota provide PET scans. The clinic has several machines that do both PET and CT scans. Mayo Clinic staff members make the tracers used in PET scans on-site.

For appointments or more information, call the Central Appointment Office at 507-538-3270 7 a.m. to 6 p.m. Central time, Monday through Friday or complete an online appointment request form.

See information on patient services at the three Mayo Clinic locations, including transportation options and lodging.

Doctors and scientists who have training in PET scans and other imaging technology study how best to use PET scans to predict and diagnose a wide range of diseases and conditions. In 2012, Mayo Clinic received Food and Drug Administration approval to produce and administer choline C-11 injection, an imaging agent used during PET scanning to help detect sites of recurrent prostate cancer. Mayo Clinic is the first institution in North America approved to produce choline C-11.

Publications

See a list of publications by Mayo Clinic authors on PET scans on PubMed, a service of the National Library of Medicine.

May 06, 2014