General Info about PET Scans

What Is a PET Scan?

A positron emission tomography (PET) scan is an imaging test that allows your doctor to check for diseases in your body.

The scan uses a special dye containing radioactive tracers. These tracers are either swallowed, inhaled, or injected into a vein in your arm depending on what part of the body is being examined. Certain organs and tissues then absorb the tracer.

When detected by a PET scanner, the tracers help your doctor to see how well your organs and tissues are working.

The tracer will collect in areas of higher chemical activity, which is helpful because certain tissues of the body, and certain diseases, have a higher level of chemical activity. These areas of disease will show up as bright spots on the PET scan.

Cancer cells have a higher metabolic rate than noncancerous cells. Because of this high level of chemical activity, cancer cells show up as bright spots on PET scans. For this reason, PET scans are useful both for detecting cancer and for:

       seeing if the cancer has spread

       seeing if a cancer treatment is working

       checking for a cancer recurrence

However, these scans should be read carefully by your doctor, as it’s possible for noncancerous conditions to look like cancer on a scan. It’s also common for solid tumors to fail to appear on PET scans.

How is a PET scan performed?

Before the scan, you’ll get tracers through a vein in your arm, through a solution you drink, or in a gas you inhale. Your body needs time to absorb the tracers, so you’ll wait about an hour before the scan begins.
How long it takes for your body to fully absorb the tracer will depend on the area of the body being scanned.

While you wait, you’ll want to limit any movement, relax, and try to stay warm. If you’re undergoing a brain scan, you’ll want to avoid television, music, and reading.

Next, you’ll undergo the scan, which can last anywhere from 30 to 45 minutes. This involves lying on a narrow table attached to a PET machine, which looks like a giant letter “O.” The table glides slowly into the machine so that the scan can be conducted.

You’ll need to lie still during the scan. The technician will let you know when you need to remain still. You may be asked to hold your breath for several seconds. You’ll hear buzzing and clicking noises during the test.

When all the necessary images have been recorded, you’ll slide out of the machine. The test is then complete.