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PROCESSING

PROCESSING. BY Hany M. Omar Associate professor of Oral Radiology. Processing is a term used to describe the sequence of events required to convert the invisible latent image , contained in the sensitized film emulsion, into the visible, permanent radiographic image. Latent Image.

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PROCESSING

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  1. PROCESSING BY Hany M. Omar Associate professor of Oral Radiology

  2. Processing is a term used to describe the sequence of events required to convert the invisible latent image, contained in the sensitized film emulsion, into the visible, permanent radiographic image.

  3. Latent Image Pattern formed by the interaction of x-rays or light with the silver halide crystals in the emulsion

  4. Mechanism of latent image formation • Selective penetration phenomena • Effect on film emulsion: • Exposed molecules • Unexposed molecules • Latent image sites will be formed in Ag halide molecules that are exposed to x-ray. Theses sites contain neutral silver atoms called “silver specks”. • Crystals could be totally exposed, partially exposed or non exposed.

  5. Totally exposed crystals partially exposed crystals Un exposed crystals Ag+ Br- Ag+ Br- / Ag Br Ag Br

  6. Developing: • Reduction of exposed silver halide crystals into black metallic silver. • Produce the black parts of the image. • Time depends on temperature of solution (in case of proper concentration and exposure parameters) • Over development: reduction of unexposed crystals

  7. Totally exposed crystals partially exposed crystals Un exposed crystals Reduction of bromide part

  8. Rinsing: • Remove the chemicals from the film • Neutralize developer alkalinity • Stop developing reaction

  9. Fixation: • Removes (clears) undeveloped silver halide crystals • Produces white areas of the image • Fixes the precipitated silver • Takes nearly double the time of development

  10. Fix the ppt Ag and wash away the undeveloped crystals

  11. Washing: • Remove all processing solutions • Takes about 15-20 minutes

  12. Drying: • Facilitates film handling without mechanical damage • Makes film ready for mounting and interpretation

  13. Chemistry of processing solutions

  14. Elon or metol and hydroquinone Converts exposed silver halide crystals into black metallic silver grains

  15. Na carbonate *Provides alkaline solution needed by developer. *Softens gelatin allowing developer to reach crystals.

  16. K Br Slows down rate of developing of unexposed crystals

  17. Na sulfite prevents developer from being oxidized by the air and combines with any oxidized developer

  18. Na thiosulfate Dissolves and removes unexposed silver halide crystals from emulsion

  19. Acetic acid Neutralizes any contaminating alkali from the developer

  20. K alum Hardens emulsion so film can be handled

  21. Na sulfite Inhibits decomposition (oxidation) of clearing agent

  22. Processing solutions • May be obtained in the following forms: • Powder • Liquid concentrate • Ready to use liquid • Replenishment: • Addition of super concentrated solution to the processing solutions to compensate for the loss of volume and strength that results from oxidation. • Both developer and fixer solutions must be replenished daily. • Changed every 3-4 weeks.

  23. Darkroom Basic requirements: 1- site 2- Adequate size

  24. 3- Cleanliness

  25. 4- ventilation, temperature and humidity Healthy working conditions for personnel

  26. 5- light tightness

  27. Normal incandensation light

  28. Intraoral, extraoral Intraoral

  29. Safelight Test

  30. 6- Processing tanks

  31. 7- film hangers

  32. Methods of processing • Manual processing Visual method Time temp method • Automatic processing

  33. Manual Processing Check solution levels Stir solutions frequently Check temperature often Agitate film hangers in solutions Wash for 20 min

  34. Automatic Processor Drying Elements Film Entry Film Exit Developing Fixing Water Solution Solution Rinse

  35. dryer water rinse fixer developer insert films

  36. Daylight Loader Intraoral films only Must be placed in an area of subdued lighting

  37. So remember that:- • Structures that permit passage of x-ray  exposure of silver halide crystals  deposition of black metallic silver by developing  black areas on the radiograph (radiolucent areas). • Structures that resist passage of x-ray  no exposure of silver halide crystals  removal of undeveloped silver halide crystals by fixation  white areas on the radiograph (radiopaque areas). • The visible image that results on a dental radiograph is made up of black, white and gray colors.

  38. ????????? QUESTIONS

  39. Thank You and Good luck

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