Lapis ISSN 2398-2969

Radiography: processing

Contributor(s): Vetstream Ltd, David Vella

Formation of the latent image

  • When film is exposed to x-rays and light from intensifying screens the silver halide crystals are affected forming thelatent image
  • The latent image is not visible since, although the reduction of silver halide to metallic silver has begun there is not enough of this to appear black. 
  • The silver halide in the emulsion is in the form of a crystal lattice containing (negative) bromide ions and (positive) silver ions. 
  • Some of these ions are free to move within the crystal lattice. 
  • Around the crystal lattice is a "barrier" of electrons. 
  • During manufacture a defect is introduced into the crystal    →   sensitivity speck   Radiation physics: sensitivity speck  .
  • When the film is exposed to ionizing radiation: 
    • Some of the bromide ions in the lattice emit electrons. 
    • These electrons travel rapidly to the sensitivity speck which acts as anelectron trap
    • The electron trap builds up a negative charge. 
    • Silver ions are attracted to the negative charge. 
    • The positive charge of the silver ions is neutralized by the electrons in the trap (reduction) and silver atoms are produced. 
    • The presence of metallic silver in the crystal lattice makes a break in the electron barrier which surrounded it and it is therefore susceptible to the action of developer.

Development

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Rinsing

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Fixing

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Washing

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Drying

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Further Reading

Publications

Refereed papers
  • Recent references fromPubMedpublished during the last 12 months.


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