PET-CT Scans

About PET-CT Scans

What Is a PET Scan?

A PET (positron emission tomography) scan creates an image of your body's metabolic activity and shows the rate at which your body's cells break down and use sugar (glucose).

This is done by injecting a small amount of radioactive material (Fluoro-D-Glucose, or FDG) into your blood stream and waiting for it to disperse to the area of focus. The PET scan is then performed to detect the radioisotope and create an image on the computer screen.

PET is also useful in diagnosing certain cardiovascular and neurological diseases because it highlights areas with increased, diminished or no metabolic activity, thereby pinpointing problems.

What Is a CT Scan?

A CT (computed tomography) scan is a noninvasive medical test that uses special x-ray equipment to produce multiple images or pictures of the inside of the body and a computer to join them together in cross-sectional views of the area being studied.

CT scans of internal organs, bone, soft tissue and blood vessels provide greater clarity than conventional x-ray exams.

What Is a PET-CT Scan?

PET-CT is a relatively new diagnostic imaging exam that combines the functional information from a PET scan with the anatomical information from a CT scan. When a CT scan is superimposed over a PET scan, doctors can pinpoint the exact location of abnormal activity. They can also see the level and extent of that activity. Even when an abnormal growth is not yet visible on a CT scan, the PET scan may show the abnormal activity.

Common Uses

PET-CT scans are commonly used to find changes in the body during the early stages of disease and for staging and restaging of cancers.

Safety – CT

As with other medical procedures, CTs are safe when used with care. Radiologists and x-ray technologists have been trained to use the minimum amount of radiation necessary to obtain the needed results. The amount of radiation used in most examinations is very small and the benefits greatly outweigh the risk of harm.

CT X-rays are produced only when a switch is momentarily turned on. As with visible light, no radiation remains after the switch is turned off.

Safety – PET

Because the doses of radiotracer administered are small, diagnostic nuclear medicine procedures result in minimal radiation exposure. Thus, the radiation risk is very low compared with the potential benefits.

Nuclear medicine has been used for more than 5 decades, and there are no known long-term adverse effects from such low-dose exposure.

Allergic reactions to radiopharmaceuticals may occur but are extremely rare.

Women should always inform their physician or technologist if there is any possibility that they are pregnant or if they are breastfeeding their baby.

PET exams also use x-ray-like radiation. But the method of use is quite different from x-rays, and they produce very different looking images.

In nuclear medicine, another precaution is advised for women who are breast-feeding a child. Some of the pharmaceuticals that are used for the study can pass into the mother's milk and subsequently the child will consume them.

To avoid this possibility, it is important that a nursing mother inform her physician and the nuclear medicine technologist about this before the examination begins. Usually, you will be asked to discontinue breast-feeding for a short while, pump your breasts in the interim and discard the milk. Breast-feeding can often resume shortly afterwards.

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Department of Radiology
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Last Updated: 04-09-2014
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Disclaimer: The information on this website is for general informational purposes only and SHOULD NOT be relied upon as a substitute for sound professional medical advice, evaluation or care from your physician or other qualified health care provider.