Positron Emission Tomography (PET)

As the first community hospital in Los Angeles County to introduce PET imaging, Torrance Memorial Medical Center has been and remains a leader in the use of this innovative and important technology here in our South Bay area. We currently perform and interpret more than 1300 PET/CT scans each year.

What is PET/CT?

Positron emission tomography (PET) is a type of imaging that uses nuclear medicine to detect problems at the molecular level. This sophisticated technology can identify abnormalities in cellular activity at a very early stage, generally before anatomic changes are visible. When combined with computed tomography (CT), which provides a detailed picture of the body's internal anatomy, PET/CT combines the strength of these two well-established modalities into a single state-of-the-art scan that provides important information to help guide potentially life-saving treatments.

• PET/CT is used in oncology to determine the extent (stage) of many types of cancers, to monitor treatment effectiveness and to check for recurrence.
• In cardiology, PET/CT can assess coronary artery disease. After a heart attack, PET/CT can determine if the heart muscle would benefit from bypass surgery.
• In neurology, PET/CT can help in the diagnosis of dementia and Alzheimer's disease.

What to Expect During a PET/CT Scan

A PET/CT scan is typically done on an outpatient basis. The appointment lasts between one-and-a-half to two hours. Generally, you'll be asked not to eat anything for several hours, since digestion may alter the distribution of the PET tracer in the body. You will be encouraged to drink water but to avoid other liquids, since any ingested sugar may alter the reliability of the study. Diabetic patients may be given specific instructions.

PET/CT involves injecting a small amount of a radioactive tracer into a vein in the arm or hand. You will feel a small pin prick sensation when the needle is inserted. When the radiotracer is injected, some patients feel a cool sensation in the arm, but generally there are no other side effects. The radiotracer typically needs to circulate for approximately one hour, so you will sit comfortably in a reclining chair during this waiting period.

The PET/CT scanner is a large machine with a doughnut-shaped hole in the middle. The actual time spent in the scanner is usually 30 minutes or less. As you pass through it, the scanner's multiple detectors pick up the radiotracer emission and highlight areas of increased uptake in your body. Sophisticated computer software is used to process the information so that it can be displayed in three dimensional planes on a computer workstation. A radiologist will interpret the images and send a report to the referring physician. The report is typically available within 48 hours and will be discussed with you by your physician.

PET/CT & Radiation

Because the dose of radiotracer administered during a PET/CT is small, there is relatively low radiation exposure. The radiation risk is very low and typically outweighed by the potential benefits of the study. Through the natural process of decay, the small amount of injected radiotracer will lose its radioactivity over time. It will also pass out of your body through the urine. Therefore, it is important to drink plenty of water to help flush the radioactive material from your body.

How Will You Learn About Your Results?

The technologist will not give you the test results directly, as the images still need to be reviewed by a radiologist. After reviewing the study, the radiologist will send an official report to your physician, who can then discuss the results with you.