What Is a CAT Scan?

CAT Scan Produces Cross-Sectional Image of the Body

Woman going into CT scanner
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CAT Scan Explained

A CAT scan, also referred to as computerized axial tomography, CT scan, or computed tomography, is a non-invasive imaging test used to help diagnose medical conditions. Using x-ray equipment and specialized computers, a CAT scan can produce multiple images that are cross-sectional views of a specific area of interest inside the body.

How Does a CAT Scan Work?

If you are having a CAT scan, you will be told to lie on a motorized table that will move you through the opening of the CAT scan imaging system.

During some CAT scans, you will be given an intravenous dye (contrast) to help identify blood vessels and sites of inflammation. There is an x-ray source and a detector within the housing of the CAT scan imaging system. The x-ray source and detectors are located across from each other in a ring, called a gantry, that rotates around you.

The x-ray source produces a beam of x-rays, in the shape of a fan or triangle, that passes through the section of the body being scanned. A detector, located opposite the x-ray source, records the x-rays passing through the body as a series of snapshot images. Many different snapshots are collected from various angles for each complete rotation of the x-ray source and detector. Then, it's the job of the computer to reconstruct the individual images into a series of cross-sectional images of that particular part of the body, making it useful for diagnostic purposes.

When Is a CAT Scan Ordered?

A CAT scan is able to provide very detailed views of all types of tissue. It is typically ordered when information is needed beyond what a regular x-ray can provide. A CAT scan is used to diagnose a wide array of medical conditions, including cancer and vascular diseases. It is useful for arthritis and musculoskeletal conditions, too, especially for problems with the spine, hands, and feet, where images of small bones and surrounding tissues (including muscles and blood vessels) are essential for diagnosis.

Risks and Benefits Associated With CAT Scan

Generally, the benefits of a CAT scan are that it is painless, non-invasive procedure that offers very detailed information. Unlike a regular x-ray, a CAT scan provides images of soft tissue as well as bone. Unlike an MRI, the CAT scan is not as sensitive to your movement and can be used for patients who have implanted medical devices. No radiation remains in your body after a CAT scan. The main risk associated with a CAT scan is exposure to radiation. If your scan also involves intravenous contrast, then there also is a small risk of allergic reaction and/or kidney problems. In most cases, however, the benefits outweigh the risks.

Sources:

Radiation Emitting Products. Computed Tomography (CT). Accessed 2/26/11.
http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115317.htm

CT - Body. RadiologyInfo.org. March 15, 2010.
http://www.radiologyinfo.org/en/info.cfm?pg=bodyct

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