Together We Can -- Newsletter of the Joan Karnell Cancer Center

Summer 2005

A Nutritional Journey
Message From the Administrator
Understanding Positron Emission Tomography (PET Scan)
Psychological Services
Favorite Recipes
Honors, Awards & Publications
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Understanding Positron Emission Tomography (PET Scan)

How many times have you heard these terms: CT, CAT scan, MRI, or PET scan? These types of radiology tests are routinely ordered during the diagnosis and treatment of cancer.

To help patients and their families better understand the various imaging techniques, the Joan Karnell Cancer Center newsletter presents a new series, Understanding the ABC's of Imaging. This issue features Positron Emission Tomography.

Positron Emission Tomography (PET) is a scan which provides diagnostic information unavailable from other imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI). An MRI or CT provides images of the physical structure of the body. A PET scan provides imaging that shows how the body's organ systems function and how cells grow.

PET is able to show whether tissue is normal or abnormal based on cellular metabolism. This information allows the doctor to assess chemical and physiological changes related to metabolism. Because metabolic changes appear before anatomic changes, PET images can show changes long before they are visible on a CT or MRI.

PET can precisely locate a tumor, tell if it is benign or malignant, and measure response to chemotherapy and/or radiation. In addition, it is used to help diagnose many neurological problems, such as Alzheimer's disease and epilepsy, and to identify certain types of coronary heart disease.

Preparing for a PET Scan
A PET scan is painless and takes approximately two hours to complete. You should not do any strenuous exercising for 24 hours prior to the test. In regards to eating, patients must fast overnight or for at least six hours prior to the test. Diabetic patients should contact the PET center for more specific instructions. Everyone should drink plenty of water before and during the fast.

The PET scan procedure begins with a simple injection of flourodeoxyglucose (FDG). This is a radiopharmaceutical that resembles glucose (sugar) already in your body. The FDG gives off signals which are picked up by the scanner. You will be asked to rest quietly while the FDG circulates throughout your body. You will then be positioned on the scanning bed. You must remain still as the images of your body are acquired. The imaging time usually takes 35-45 minutes.

The future for PET is extremely promising. New advances allow the PET and CT images to be used together to provide doctors with even more accurate information on the location of tumors. This information can be used to plan surgery and in radiation treatment. PET/CT fusion are already available at Pennsylvania Hospital.

For more information, see these answers to frequently asked questions:

How much radiation exposure does a PET scan produce?
Because the radioisotope used in a PET scan is short-lived, the amount of radiation exposure the patient receives is the same as from two chest X-rays.

Do people experience any reactions as a result of a PET scan?
Patients typically do not experience any reactions as a result of the PET scan because the tracer material is processed by the body naturally. Therefore, no side effects are expected.

I've only heard about PET scans recently. Are they new?
PET has been used for more than 30 years. However, only a few institutions had access to this powerful diagnostic tool. As the technology expands, this diagnostic tool is becoming more widely available.

Will my insurance cover PET?
Coverage of PET is limited. By itself, PET is an expensive test. Contact your insurance provider to not only learn if PET is covered, but also to determine which procedures are covered and under what circustances.


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