A PET CT scan is a noninvasive, painless imaging procedure that helps your radiologist evaluate the structure and function of your organs and tissues.

PET stands for positron emission tomography, and CT stands for computed tomography. Together, both scans provide a picture of your organ and tissue function.

A PET CT scan is a critical tool that doctors use to determine how advanced cancer is, and the best way to treat it. The scan precisely measures the extent of disease to a greater degree than any other imaging tool we currently have.

PET scans are most often used to:

• Detect cancer or cancer recurrence
• Detect heart disease
• Determine if and how much the cancer has spread
• Establish the effectiveness of your current treatment plan
• Evaluate brain abnormalities related to dementia or seizure disorders

How PET CT scans work

For a PET CT scan, you will be injected with a safe amount of radioactive material, called radiotracer.

A combination of PET and CT scanners then measure the amount of radiotracer your body absorbs and produce detailed images that represent the structure and function of your organs and tissues. The PET scan measures:

• Blood flow
• Oxygen use
• Sugar (glucose) metabolism

The scanners provide images that show the exact location of any abnormal metabolic activity in the body and offer a more accurate diagnosis than when the PET and CT scans are performed separately.

Why we use PET CT scans 

PET CT scans and other nuclear medicine imaging studies look at the processes occurring in the body, rather than just looking at images of your anatomy. Areas of your body that show greater intensity of activity are called "hot spots." Hot spots indicate that there is a high level of chemical activity occurring in that portion of your body.

PET CT scans are especially helpful in assessing:

• Cervical cancer
• Colon cancer
• Breast cancer
• Lung cancer
• Lymphoma
• Melanoma

Benefits of PET CT scans

You will only be asked to undergo a PET CT if your doctor believes it is essential to your care. In many cases, it is the only way for your doctor to get an accurate picture of your health condition. This test can detect early onset of disease better than other imaging tests.

Because a PET CT scan provides more detailed, reliable information about your health, your treatment may be shorter and have better outcomes.

Limitations and risks of PET CT scans

The PET CT scan may not produce images as visually clear as those produced by a traditional CT, MRI (magnetic resonance imaging) or other imaging procedure.

Diagnostic nuclear medicine procedures like PET CT scans have been used for more than 50 years. The risks are small, and the procedure results in low radiation exposure. There are no known long-term side effects from low-dose radiation exposure.

Though allergic reactions to the radiotracer can occur, they are rare and often mild.

How to prepare for a PET CT scan 

Your doctor or nurse will give you specific instructions prior to your PET CT scan, particularly if you are diabetic.

During the exam, you will either wear your own clothing or be asked to change into a medical gown. You will be asked to remove jewelry, hairpins, hearing aids, eyeglasses, and dentures.