FS Mt

• Latent image - the invisible image that is induced in the silver halide crystal
• Manifest image - the image that exists on film after processing
• Purpose of processing


  1. Change silver halide crystals from film emulsion (after exposure to x-ray or light photons) to black metallic silver

  2. Latent image (invisible until processed) is developed into a visible image

  3. Improper or careless processing can cause poor diagnostic quality
• Pako Company


  • The first to introduce automatic processor in 1942
  • 120 films per hour
  • Cycle time for processing one film was approximately 40 minutes
• Eastman Kodak Company


  • Introduced the first roller transport system for processing medical radiographs in 1956
  • 6-minute processing time
  • Introduced 90-second rapid processing in 1965
• Processing steps


  1. Wetting

  2. Developing

  3. Rinsing

  4. Fixing

  5. Washing

  6. Drying
• Wetting - swells the emulsion so that subsequent chemical baths can reach all parts of the emulsion uniformly
• Developing - stage of processing during which the latent image is converted to a visible image
• Rinsing - film is rinsed in an acid solution designed to stop the developing process and remove excess developer chemicals from the emulsion
• Fixing - the process of clearing unexposed silver halide crystals from the emulsion and hardening the emulsion to preserve the image
• Washing


  Removes any remaining chemicals from the previous processing steps
• Drying


  Removes the water used to wash it and to make the film acceptable for handling and viewing
• Development


  The chemical process that amplifies the latent image
• Reducing agents


  • Hydroquinone
  • Phenidone
• Synergism


  The action of two agents working together is greater than the sum of the action of each agent working independently
• Buffering agents


  • Sodium carbonate
  • Sodium hydroxide (Lye)
• Restrainers


  • Potassium bromide
  • Potassium iodide
• Preservative


  Controls the oxidation of the developing agent by air (aerial oxidation)
• Hardener


  Controls swelling and softening of the emulsion
• Sequestering agents


  Form stable complexes with metallic ions and salts
• Stop bath


  Neutralizes the residual developer in the emulsion and stops its action
• Activator


  Neutralizes the pH of the emulsion and stops developer action
• Fixing agent / Clearing agent


  Removes unexposed and undeveloped silver halide crystals from the emulsion
• Silver sulfide stain


  The most common cause of poor archival quality
• Hardener


  Accelerates the shrinking process and causes the emulsion to become more rigid or hardened
• Preservative


  Maintains the chemical balance because of the carryover of developer and fixer from one tank to another
• Washing


  Washes away any residual chemicals remaining in the emulsion, particularly hypo that clings to the surface of the film
• Drying


  Warm dry air is blown over both surfaces of the film as it is transported through the drying chamber
• Automatic processing


  • Transport system
  • Temperature control system
  • Circulation system
  • Replenishment system
  • Dryer system
• Transport system


  Controls processing by controlling the time the film is immersed in each wet chemical
• Temperature control system


  Developer temperature is maintained at 35°C (95°F), wash water is maintained at 3°C (5°F) lower
• Circulation system


  Continuously pumps the developer and the fixer, thus maintaining constant agitation
• Replenishment system


  Meters the proper quantities of chemicals into each tank to maintain volume and chemical activity
• Dryer system


  Extracts all residual moisture from the processed radiograph
• Radiographic technique

  • Optical density
  • Contrast
  • Image detail
  • Distortion
• Optical density


  The degree of blackening of the finished radiograph
• Optical density increases


  Directly with mAs, inversely with SID
• The kVp setting must be changed by approximately 4% to produce a perceptible change in OD
• Contrast


  The difference in OD between adjacent anatomical structures, or the variation in OD on a radiograph
• Contrast


  The function of contrast in the image is to make anatomy more visible