CT Scanners

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CT Scanners

CT stands for computed tomography.

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Basic principles

  • The patient lies in a void between X-ray tube and detector.
  • X-ray tube rotates around subject in a plane, detectors may rotate on opposite side or be an array of multiple fixed detectors.
  • Highly collimated (narrow), monochromatic beam of X-rays used.
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Basic principles cont.

  • Slice of subject scanned and computer processes results to form image of the slice.
  • X-ray tube and detectors are 'translated' or moved to produce an image of next 'slice'.
  • Images of multiple slices are produced which are combined by computer into a 3-D image which can be rotated and viewed from any angle.
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  • Full cross-sectional image
  • Better resolution than ultrasound
  • Non-invasive
  • Better than conventional X-ray for imaging brain, abdomen, bone fractures
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  • Highly ionizing, so needs to be used with care to keep the dose low
  • Expensive
  • Patients may have to hold their breath
  • Contrast may be limited

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