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Definition of CT scan

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

CT scan: Computed tomography scan. Detailed images of internal organs are obtained by this type of sophisticated X-ray device. CT stands for computed tomography.

The CT scan can reveal anatomic details of internal organs that cannot be seen in conventional X-rays. The X-ray tube spins rapidly around the patient and the X-rays strike numerous detectors after passing through the body. These detectors are connected to sophisticated computers which generate images after image processing. The radiation dose of a CT scanner is much higher than a conventional X-ray, but the information obtained from a CT scan is often much greater.

The tomograms ("slices") for CT can be created as thin as one millimeter or less. Images can be displayed in numerous display planes, and can also be displayed as 3-D images.

The CT scanner was invented in 1972 by the British engineer Godfrey N. Hounsfield (later Sir Godfrey) and the South African (later American) physicist Alan Cormack. CT scanning was already in general use by 1979, the year Hounsfield and Cormack were awarded the Nobel Prize in Medicine or Physiology for its development.

The CT scan is also known as the CAT (computerized axial tomography) scan.

Reviewed on 12/4/2018

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