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  2. 2. SEMINAR
  4. 4. DEFINITION Processing is a collective title given to a series of operations carried out in the dark room, which effect chemical changes in the exposed radiographic film, making the invisible latent image, contained in the sensitized film emulsion into a visible, permanent radiographic image
  5. 5. LATENT IMAGE  A radiographic film is a recording medium used in dental radiography. When this film is exposed to the information carrying beam of photons exiting an object, the photosensitive silver halide crystals in the film emulsion interact with these photons and are chemically changed. These chemically altered crystals are said to constitute the latent (invisible) image of the film
  6. 6.  These chemical changes in the crystals increase the liability of crystals to chemical action of the developing process that converts the latent image into manifest (visible) image
  7. 7. FORMATION OF THE LATENT IMAGE  The film emulsion is made of silver bromide crystals and silver iodide crystals that is precipitated in gelatin and layered on a thin sheet of transparent base  The silver halide crystals are chemically sensitized by the presence of sulphur compounds which cause physical irregularities in the crystal produced by iodide ions , and these are called latent image sites
  8. 8.  The function of latent image site is to begin the process of image formation by trapping the electrons generated when the emulsion is irradiated  When the silver halide crystals are irradiated , the electron released changes bromide ion into bromine atom. This will produce kinetic energy with which it moves in the crystal and strikes the image site imparting a negative charge to that region
  9. 9.  Free positively charged interstitial silver ions are attached to the negative latent image site and neutralize the image site with the result that an atom of metallic silver is deposited at the site. After exposure e of a film to radiation, the aggregate of silver atoms at the latent image sites, comprises the latent image. It is the metallic silver at each latent image site that catalyses the development of the halide crystal in which it formed and renders the crystal sensitive to development and image formation
  10. 10. FILM PROCESSING  The primary action of processing solution is to convert the crystals with latent image into black metallic silver grains that can be visualized and to remove the unexposed silver bromide crystals  Latent image is made visible through the following processing procedures  The film is placed in a chemical known as the developing solution for a specific amount of time and at a specific temperature
  11. 11.  Developer distinguishes between unexposed and exposed silver halide crystals  Reduces exposed silver halide crystals into metallic silver and creates black areas in the radiograph  Unexposed remains unaffected  Rinsed in water to remove remaining developer solution
  12. 12.  Next , the film is placed in a special chemical known as fixer solution  Fixer solution removes the unexposed silver halide crystals and creates white or clear areas on dental radiograph  Following the fixing process , the film is washed in water to remove any remaining traces of chemical solution  Drying : after rinsing the film , it is dried. The film is placed in a drying cabinet or hung up in a well ventilated dust free room
  13. 13. FILM PROCESSING SOLUTIONS  These may be obtained in the following forms :  Powder  Ready to use liquid  Liquid concentrate  The special chemical solutions are :  Developer solution  Fixing solution
  14. 14. DEVELOPER SOLUTION  REDUCING AGENTS  Hydroquinone : - It is concerned with the production of high contrast in the radiograph  Metol or Elon :- It helps develop the shades of gray on the film and brings out the details  When used together hydroquinone and metol produce an adequate contrast and detail, at 20 degree C  Metol phenidone :- this serves as the first electron donor that converts silver ions to metallic silver at the latent image site
  15. 15.  PRESERVATIVE  Sodium sulphite :- this inhibits the tendency of the developing agent to combine with the oxygen dissolved in water or in the air. Therefore acts as a preservative and keeps the solution in an usable condition for several weeks  Oxidation of the developing agents forms colored substances which would stain the film and add to the film fog
  16. 16.  ACTIVATOR  Potassium carbonate or sodium carbonate :provide and maintain the degree of alkalinity in which the developing agent can function. Also known as accelerator  RESTRAINER  Potassium bromide :- it slows down the reduction action of the developing agents
  17. 17.  HARDENER  Glutaraldehyde :- to prevent the emulsion from softening and sticking to the rollers  FUNGICIDE :- to prevent bacterial growth  BUFFER :- to maintain p H  SOLVENT :- water
  18. 18. FIXING SOLUTION           CLEARING AGENT Ammonium thiosulphate :- removes silver bromide PRESERVATIVE Sodium sulphite :- prevents oxidation of clearing agent ACIDIFIER Acetic acid :- keep the fixer pH constant HARDENER Aluminum chloride :- form complex with gelatin SOLVENT Water
  19. 19.  REDUCTION  A photographic reducer contains an oxidizing agent, potassium ferricyanide which oxidizes the silver to silver ferrocyanide , which in turn is dissolved by the solution of sodium thiosulphate. This is known as the farmer’s reducer and consists of two solutions  Solution A : potassium ferricyanide 75 grams  Solution B : sodium thiosulphate crystals 240 grams
  20. 20.  CHEMICAL INTENSIFICATION OF RADIOGRAPHS  In – 4 chromium intensifier  In -5 silver intensifier  Copper iodide intensifying solution  XR -10 intensifying solution  Line toner solution
  21. 21. THE DARKROOM  Function :- provide a completely darkened environment where the X-ray film can be handled and processed to produce a diagnostic image in an efficient, precise and standardized procedure
  22. 22.  GENERAL  LAYOUT Size of the darkroom :- 3 feet x 3 feet for an individual dentist and 16 to 20 square feet for a group  Size will vary depending on :-  Volume of radiographs processed  Number of persons using darkroom  Type of processing equipments  Space required for duplication of film and storage
  23. 23.  REQUIREMENTS OF DARK ROOM  Sufficient space  Should be 3 feet away from processing tank  Should be ventilated  Temperature of 70 degree and humidity of 50-70% is maintained  Should include hot and cold running water
  24. 24.  ILLUMINATION  Complete darkness and must exclude all visible light- light tight or light proof is accomplished by :exclusion of all external lights use of light tight door  Use of both white light and safe light  White light illumination is required during cleaning tanks and preparing the solutions
  25. 25.  SAFE  LIGHT ILLUMINATION Should be of low intensity 3 zones :i. dimmest zone ii. medium zone iii. bright zone   Excessive exposure of film to safe light illumination will result in fog, 3 factors :-
  26. 26.  Type of filters:-  Moralite filter  Wratten series 6 B filters  Red GBX-2 safe light filter  Intensity of illumination :-  Wattage of bulb should be 7 ½ to 15 watts  The distance of the safe light above the work area should be 4 feet  Time of exposure :- more the film is exposed to safe light, more chance of film fogging
  27. 27.  TESTS FOR CHECKING UNSAFE ILLUMINATION  Coin test / penny test :- evaluate fogging caused by inappropriate safe light conditions  Check for light leak
  28. 28.  PROCESSING EQUIPMENT  MANUAL / HAND / TANK PROCESSING  Simplest and most efficient procedure for developing with accurate control  Processing tank consists of :-  Master tank  Insert tank  Tanks are made of :-  Stainless steel ( ISI type 316 SS with 23 % Mo )  Enamel  Earthenware  Hard rubber
  29. 29.  OTHER REQUIREMENTS INCLUDE :  Thermometer  Timer  Drying racks  Stirring rod or stirring paddle  Plastic apron
  30. 30. METHODS OF PROCESSING  Manual method  Time temperature method  Visual method  Rapid processing method  Automatic method  Monobath method  Day light method  Digitized processing method  Self developing method
  31. 31.  TIME  TEMPERATURE METHOD Mass processing of radiographs  Method  Replenish solutions  Stir the solutions  Mount the film on hangers  Processing is carried out at a temperature of 6870degree F and timer is fixed  Dry the film
  32. 32.  VISUAL  METHOD Advantage :- film can be developed to the contrast and detail desired for the particular subject  Disadvantage :- film has to be individually and is very time consuming processed
  33. 33.  RAPID PROCESSING METHOD  Film can develop in 15minutes at room temperature  Applied in endodontics and emergency situations
  34. 34.   AUTOMATIC METHOD Automatic dunking models : produces a washed film that still has to be dried  Miniature roller type : produces a dried film  Advantages :-  Process takes less than 4- 7 minutes  Uniformity  Less floor space required  No wet films to be handled  Density and contrast are consistent
  35. 35.  Disadvantages   Quality is not as high as manually developed radiograph More grain is evident in the final image High cost of equipment and maintenance  Mechanism  An in line arrangement consisting of a transport system Function of roller Move the film through developing solutions Motion keeps solutions agitated    
  36. 36.  MONOBATH METHOD Developer and fixer are combined in one solution  Advantage : It is ideal for root canal treatment or in cases of quick spot diagnosis     Disadvantages :Alkaline type of fixer very rapidly oxidizes under atmospheric conditions Results are not satisfactory as in conventional processing as the fixing starts while the developing process is in progress
  37. 37.  DAY LIGHT METHOD  No need of darkroom  Emulsion consists of yellow dye and the film appears yellow and black
  38. 38.  DIGITIZED PROCESSING METHOD  CR system : IP cassette is used instead of cassette with an X-ray film  DR system : cassette is replaced by a sensor which is directly connected to the workstation
  39. 39.  SELF DEVELOPING FILMS  Advantages :No dark room is required Time saving         Disadvantages :Poor image quality Image deteriorates with time No lead foil inside the packet Film packet is flexible and easily blent Films are difficult to use in positioning holders