CT Scan

What Is A CT Scan?

Last modified: 
15/04/2013 - 13:19

Computed tomography (CT), also known as Computed Axial Tomography (CAT), is a painless, sophisticated x-ray procedure. Multiple images are taken during a CT or CAT scan, and a computer compiles them into complete, cross-sectional pictures ("slices") of soft tissue, bone, and blood vessels.

A CT scan obtains images of parts of the body that cannot be seen on a standard x-ray. Therefore, these scans often result in earlier diagnosis and more successful treatment of many diseases.

A CT scan is considered to be a safe examination. While CT imaging does involve x-rays, the diagnostic benefits generally outweigh the risks of x-ray (radiation) exposure.

In some CT scans, contrast agents or sedatives may be used. A contrast agent is a substance used to "highlight" an organ or tissue during examination and is sometimes referred to as a "dye." Again, the benefits of early, accurate diagnosis generally outweigh any risks associated with the potential side effects of these agents.

CT scanning was developed during the mid-1970s. The original systems were dedicated to head imaging and were very slow-it took hours to acquire the images for each individual slice. The newest scanners collect as many as four slices of data in less than 350 microseconds.

This great improvement in the speed of CT scanning has been accompanied by increased patient comfort and higher resolution images. And, as scan times have become faster, the time of x-ray exposure has decreased, providing better image quality at lower x-ray doses.

Contributing Author: Guy Slowik FRCS

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From Andrew Maynard - Chair of the University of Michigan Department of Environmental Health Sciences, with help from David Faulkner - 2013 Master of Public Health graduate.