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What are CT and MRI scans?

In 1967 British engineer Godfrey Hounsfield (1919– ) designed a system called computerized axial tomography (CAT or CT). This device uses X-ray beams, which are directed in patterns through a patient's body, to give detailed cross-sections that a computer combines into a three-dimensional picture. Different kinds of human tissue block or absorb X rays at different rates, so the computer can distinguish the different organs by their patterns of X-ray absorption and color-code the images it produces on a video screen. As computers became more powerful, CT scanners improved; yet because they use X rays and large doses of radiation are harmful, researchers continued to look for new scanning methods.

Magnetic resonance imagery (MRI) uses radio waves to produce three-dimensional images of the body from any angle and direction. The patient is placed inside the MRI machine, which creates a strong magnetic...

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1. Origins
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1. Middle Ages