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Processing

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					Processing
   Professor, Nancy Rivaldo
   Monroe Community College
Introduction
          Compounds of silver & halogens
           are sensitive to x-radiation
          Film consists of a base covered
           with emulsion of silver halide
           crystals embedded in gelatin
          Gelatin keeps crystals evenly
           suspended over the base
Cont.

           Gelatin swells in water exposing
            the silver halide crystals to the
            chemicals in the developing
            solution
           Gelatin shrinks as it dries leaving a
            smooth surface that becomes the
            radiograph
Selective Reduction

     During processing a selective
     reduction of exposed silver halide
     crystals takes place which means
     nonmetallic elements, the halides,
     are removed and only the exposed
     (metallic) silver remains
What Happens?
        Film exposed to x-radiation
        Energy of photon absorbed by
         silver halide crystals in emulsion
         (photoelectric interaction)
        An image is captured
        Image not visible (latent)
Cont.
         Image made visible through
          processing
         Film placed in developer

         Exposed halide (nonmetallic) is

          removed from the silver
         Silver turns black and remains

        Silver halide crystals that have been
          ionized changed into black grains
Cont.
        Black metallic silver remaining forms
          the image and the exposed area of
          the emulsion is visible

        Image is made up of grains of black
          metallic silver
        Crystals that have not been ionized
          will remain in crystal form and not
          changed during developing stage
Cont.
        Amount of silver deposited will vary
         with thickness of tissue penetrated

        --soft tissue = black = radiolucent

        --dense tissue = white where rays
           blocked = radiopaque
Time Temperature
Technique
    The basis for this is that the optimum
      amount of precipitation of silver for
      the amount of x-ray energy
      delivered to the object takes place
      in a specified amount of time with
      the developing solution at a certain
      temperature. (Therefore, if films
      are left in the developer too long
      more silver precipitates then was
      intended)
Developer Chemicals
     1.   Developing or Reducing Agent
     2.   Alkalizer, accelerator or activator
     3.   Preservative
     4.   Restrainer
Reducing Agent

      Hydroquinone--works slowly but
       steadily to build density and
       contrast
      Elon--produces detail slowly
      Function of reducing agent is to
       change exposed crystals to black
       metallic silver
Alkalizer
   Sodium carbonate
   2 functions:
    --softens & swells emulsion gelatin
    to allow reducing agent to reach
    the crystals
    --provides required alkaline
    medium for reducer to work
Preservative
   Sodium sulfite
   Antioxidant
Restrainer
   Potassium bromide
   Controls action of developing
    agent
   Prevents chemical fog
Fixer Chemicals
   Clearing or fixing agent
   Acidifier
   Preservative
   Hardener
Clearing Agent

          Sodium or ammonium thiosulfate
          Removes unexposed or
           undeveloped crystals from
           emulsion
Acidifier
   Acetic acid
   2 functions:
    --provides required acidity for fixing
    agent to work
    --provides acid medium to
    neutralize alkali of developer and
    stops action of developer
Preservative
   Sodium sulfite
   Prevents oxidation
Hardener
   Potassium aluminum
   Shrinks and hardens the gelatin
Wetting Agent
   Used in developer to hasten film
    developing
   Reduces surface tension of film
   If a properly washed film is
    immersed for 1 minute in water to
    which wetting agent has been
    added the film will dry faster
Cutting Reducer

   Farmer’s Solution
   Used in an emergency to lighten
    films
   Will even lighten film exposed to
    white light
Manual Processing
Steps
          Develop for 5 minutes at 68
           degrees Fahrenheit (place film in
           developing solution using an
           agitating motion)
          Using an agitating motion rinse film
           for 20 to 30 seconds
          Fix for 4 minutes
          Wash for 10 minutes in running
           water
          Dry film thoroughly
Automatic Processing
          Uses mechanical transport
           systems
          Uses higher temperatures
          Phenidone replaces elon for gray
           tone production
          Hardening agent (gluteraldehyde)
           and antiswelling agent (sulfide)
           added to developer to prevent
           emulsion from sticking to rollers
Cont.
           Hardening agent also added to
            fixer to prevent sticking
           Sequence is developer, fixer, rinse
            and dry

				
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posted:1/6/2012
language:English
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