Computed Tomography, also known as computed axial tomography, or CAT scan, medical technology that uses X rays and computers to produce three-dimensional images of the human body. Unlike traditional X rays, which highlight dense body parts, such as bones, CT provides detailed views of the body's soft tissues, including blood vessels, muscle tissue, and organs, such as the brain. While conventional X rays provide flat two-dimensional images, CT images depict a cross-section of the body.
A patient undergoing a CT scan rests on a movable table at the center of a donut-shaped scanner, which is about 2.4 m (8 ft) tall. The CT scanner contains an X-ray source, which emits beams of X rays; an X-ray detector, which monitors the number of X rays that strike various parts of its surface; and a computer. The source and detector face each other on the inside of the scanner ring and are mounted so that they rotate around the rim of the scanner. Beams from the X-ray source pass through the patient and are recorded on the other side by the detector. As the source and detector rotate in a 360° circle around the patient, X-ray emissions are recorded from many angles. The resulting data are sent to the computer, which interprets the information and translates it into images that appear as cross-sections on a television monitor. By moving the patient within the scanner, doctors can obtain a series of parallel images, called slices. Doctors analyze a series of slices to understand the three-dimensional structure of the body.
To enhance an image, patients may be given an injection of a substance that will increase the contrast between different tissues. The patient may also be asked to drink a liquid that makes internal organs more clearly visible in the CT scan. Contrast agents are commonly used for scans of the chest, abdomen, and pelvis.
Health risks associated with CT are generally thought to be outweighed by the benefits of the technology. CT scans produce ionizing...
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