Canis ISSN: 2398-2942

Radiography: cassette and intensifying screen

Cassette

  • A radiographic image may be recorded in a number of ways:
    • X-ray film.
    • Digitally.
    • Camera.
    • Cine or video film.
  • The radiographic image is formed when x-rays passing through a patient and are selectively absorbed by structures within the patient.
  • The remaining x-rays fall on the film.
  • The image can be considered a shadowgram Radiation physics image production - shadowgram.
  • The film is usually held in a cassette which contains, in addition, a pair of intensifying screens.
  • Standard sizes:
    • 18 x 24 cm.
    • 24 x 30 cm.
    • 30 x 40 cm.
    • 35 x 35 cm.
    • 35 x 43 cm.

    Cassettes can be easily damaged by being dropped or mishandled.

Cassette construction

  • See diagram Radiation physics cassette construction.

Box

  • Conventional cassette is a light-proof box, hinged at one side.
  • Usually steel frame.
  • Fastenings secure but easy to use in the dark room.
  • The front is radiolucent made of:
    • Aluminium.
    • Plastic.
    • Carbon fiber.
  • Corner window where a piece of lead prevents radiographic exposure of film to allow for marking Radiography: X-ray film.
  • The back is radio-opaque to prevent scattered x-rays Radiography: scattered radiation and grid use , reflected from the table-top, passing through and affecting the film:
    • Steel with a lead foil lining.

Pressure pad

  • A soft felt pad.
  • Keeps screen in close contact with film once loaded into cassette.

    If cassette is bent or dented close contact between the screens and the film is lost resulting in image unsharpness Radiography: image quality.

Intensifying screen

  • Pressure pad keeps screen sprung against film.
  • If double-sided x-ray film is being used two screens will be present and the film is sandwiched between them.

Intensifying Screen

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Care of Intensifying Screens

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