Processing of x ray film

processing of xray film - by Shila kandel

1. Processing of x-ray film Presented by: S hila Kandel BDS 4 th year Presented to : Dr. Deepanshu Garg Department of Oral m edicine and Radiology College of Medical S ciences - TH

2. Contents Introduction Terminologies used in radiography Types of image Formation of latent image Processing the exposed film Developing Rinsing Fixing Washing

3. Darkroom equipments Darkroom Safe-lighting Manual processing tanks Thermometer Timer Drying racks Film hangers Manual processing method Changing solutions Automatic film processing Management of radiographic wastes C onclusion

4. Introduction . Film processing refers to the series of steps that converts the latent image into the visible radiographic image. A radiographic image is produced by the interaction of x-rays with photographic emulsion on a film after passing through an object. The most frequently used image receptor used in dental radiography is radiographic film.

5. Terminologies used in radiography Radiopaque T hese are the object when exposed to x-ray beam ,completely stop/absorb the x-rays and prevent them from reaching the film ,as a result silver halide crystals do not get exposed and hence conversion into metallic silver do not occur. The resultant image formed is radiopaque.

6. Radiolucent I t represents those structures through which all the x-ray beam can pass and can reach the film to react with the silver halide crystals converting them to metallic silver . T he resultant image formed is radiolucent

7. Types of image Latent image Latent image is defined as an invisible image that is produced in film emulsion by light or x-ray. Final image A final image or visible image can be described as a two-dimensional picture which is made up of a variety of black , white , and gray superimposed shadow. A latent image is converted into a visible record by series of chemical reactions which is known as processing.

8. Formation of latent image When a beam of photons exits an object and exposes an x-ray film , it chemically changes the photosensitive silver halide crystals in the film emulsion. These chemically altered silver bromide crystals constitute the latent (invisible) image on the film.

9. Before exposure ,film emulsion consists of photosensitive crystals containing primarily silver bromide suspended in a vehicle and layered on a thin sheet of transparent plastic base. These silver halide crystals also contain a few free silver ions (interstitial silver ions ) and trace amounts of sulfur compounds bound to the surface of the crystals. The sulfur compounds play a crucial role in image formation.

10. Along with physical irregularities in the crystal produced by iodide ions, sulfur compounds create sensitivity sites, the sites in the crystal that are sensitive to radiation. Each crystal has many sensitive sites, which begin the process of image formation by trapping the electrons generated when the emulsion is irradiated.

11. When the silver halide crystals are irradiated , x-ray photons release electrons from the bromide ions. The free electron move through the crystal until they reach a sensitivity site, where they become trapped and impart a negative charge to the site. The negatively charged sensitivity site attracts positively charged free interstitial silver ions.

12. When a silver ion reaches the negatively charged sensitivity site, it is reduced and forms a neutral atom of metallic silver. The sites containing these neutral silver atoms are now called latent image sites. This process occurs numerous times within a crystal , The overall distribution of crystals with latent image sites in a film after exposure constitutes the latent image.

13. (A) Sensitivity site (B) Interaction of photon with silver halide crystal (C) Formation of negatively charged photoelectron trapped at sensitivity site (D) Attraction of positively charged silver ion towards the negatively charged sensitivity site with formation of metallic silver resulting in formation of latent image

14. Processing the exposed film in developer and fixer converts the latent image into visible radiographic image.

15. Processing the exposed film Processing It is the 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 .

16. Film processing involves the following procedures : Immerse exposed film in developer Rinse developer off the film in water bath Immerse film in fixer Wash film in water bath to remove fixer Dry film and mount for viewing

17. Sequence of steps in processing Steps Time(approximate) Purpose Development 4.5-5 minutes Convert latent image to visible image Rinsing 30 seconds Removal of excess chemical Fixation 10 minutes Removal of unexposed Ag halide from emulsion and hardening Washing 15 minutes Removal of excess chemicals Drying 30 minutes Removal of water and preparation of radiograph for viewing

18. Development A chemical solution developer is used in the development process. Developer chemically reduces the exposed silver halide crystals into metallic silver grains. To produce a diagnostic image, this reduction process must be restricted to crystals containing latent image sites. T o accomplish this, reducing agents used as developers are catalyzed by neutral silver atom at the latent image sites.

19. Individual crystals are developed completely or not at all during the recommended developing times. Areas with many exposed crystals are darker because of their higher concentration of black metallic silver grains after development

20. When an exposed film is developed, developer initially has no visible effect. After this initial phase, density increases, rapidly at first and then more slowly. Eventually, all exposed crystals develop and developing agents starts to reduce the unexposed crystals. The development of unexposed crystals result in chemical fog on the film.

21. fig

22. The developing solution contains four components all dissolved in water: Developer Activator Preservative Restrainer

23. Developer Reducing agent Composition: Pyarazolidine -type compound, usually Phenidone (1-phenyl-3-pyrazolidine) Hydroquinone ( paradihydroxy benzene)

24. Function Phenidone serves as the first electron donor that converts silver ions to metallic silver at the latent image site. This electron transfer generates the oxidized form of Phenidone . Hydroquinone provides an electron to reduce the oxidized Phenidone back to its original active state so that it can continue to reduce silver halide grains to metallic silver.

25. Activator Soapy in touch Composition Sodium or potassium hydroxide Sodium bicarbonate

26. Function The developers are active only at alkaline pH values.It maintains alkalinity (pH above 11). Sodium bicarbonate acts as buffer. Activator also causes gelatin to swell for rapid diffusion of developer into emulsion.

27. Preservative Composition Sodium sulfite Function Antioxidant- protects the developers from oxidation by atmospheric oxygen and thus increasing the shelf life. Combines with the brown oxidized developer to produce a colorless soluble compound.

28. Restrainer Composition Bromide, usually potassium bromide Benzotriazole Function Depress reduction of both exposed and unexposed crystals but more effective in depressing the reduction of unexposed crystals – Antifog agent. Improves contrast.

29. Developer replenisher In the normal course of film processing, Phenidone and hydroquinone are consumed from the solution. B romide ions and other by-products are released into solution. Developer solution gets inactivated by exposure to oxygen. .

30. These actions produces a seasoned solution. Hence the developing solution of both manual and automatic developers should be replenished with fresh solution daily to prolong the life of seasoned solution. The recommended amount to be added daily is 8 ounces of fresh developer per gallon of developing solution. This assumes the development of an average of 30 periapical or 5 panoramic films per day

31. Rinsing A continuous, gentle rinsing for 30 seconds in water is necessary after developing. This rinsing process is typical for manual processing but is not used with automatic processing. Purpose : To dilute the developer and slow down the development process. To remove alkali activator thus preventing neutralization of acid fixer.

32. Fixing A chemical solution fixer is used in the fixing process. Purpose To dissolve and remove the undeveloped silver halide crystals from the emulsion as the presence of undeveloped crystals causes the film to be dark and non diagnostic. To harden and shrink film emulsion during the process.

33. Fixing solution also contains four components, all dissolved in water. Clearing agent Acidifier Preservative Hardener

34. Clearing agent After development the film emulsion must be cleared by dissolving and removing the unexposed silver halide. Composition Aqueous solution of ammonium thiosulfate (hypo). Function Dissolves and removes the unexposed silver halide grains. Forms a stable, water soluble complexes with silver ions (silver thiosulfate complex), which can be subsequently washed out of the film.

35. Acidifier Composition Acetic acid buffer system (pH 4 - 4.5). Function It provides necessary acidic medium for diffusion of thiosulfate into the emulsion and maintains adequate pH. Inactivates any residual developing agents in the film emulsion, hence blocks the further development of any unexposed crystals.

36. Preservative Composition Ammonium sulfite Function Prevents oxidation of thiosulfate clearing agent, which is unstable in the acidic environment of the fixing solution. Binds with any colored oxidized developer carried over into the fixing solution and effectively removes it from the solution, thus preventing oxidized developer from staining the film.

37. Hardener Composition Aluminium sulfate Function Complexes with gelatin during fixing and prevents damage to the gelatin during subsequent handling. Reduces the swelling of emulsion. Lessens mechanical damage to the emulsion. Limits water absorption. Shortens drying time.

38. Washing After fixing, the processed film is washed in a sufficient flow of water for an adequate time to ensure removal of all thiosulfate ions and silver thiosulfate complexes. Washing efficiency declines rapidly when water temperature decreases to less than 6o degree F . Any silver compound or thiosulfate that remains because of improper washing discolours and causes stains, which are most apparent in the radiopaque areas.

39. D rying Films are dried with the help of x-ray dryer in a dust free area. While drying, films should not touch each other to avoid sticking of the films.

40. Darkroom e quipment requirements Darkroom Safe-lighting Manual processing tanks Thermometer Timer Drying racks Film hangers

41. Darkroom A well planned dark room makes the processing easier, which should be of at least 4feet×5 feet (1.2m×1.5 m). Characteristics of dark room: Lightproof The door should have a lock to prevent accidental opening, which might allow an expected flood of light that can ruin opened films.

42. Well ventilated for the comfort of those working in the area and to exhaust the heat from the dryer and moisture from the drying films. Also, a comfortable room temperature helps maintain optimal conditions for developing, fixing, and washing solutions.

43. Controlled temperature and humidity to prevent film damage. Room temperature of 70 degree F is recommended ; if exceeds 90 degree F, film fog results. Humidity level of between 50 – 70% should be maintained; when too high, film emulsion does not dry; when too low, static electricity becomes a problem and causes film artifacts.

44. Fig : Darkroom

45. Safe lighting The processing room should have both white illumination and safe lighting. Safe lighting is special kind of lighting of relatively low-intensity illumination of long wavelength (red) that does not rapidly affect open film but permits one to see well enough to work in the area. To minimize the fogging effect of prolonged exposure, the safelight should have a 15 watt bulb and should be mounted at least 4 feet above the surface where opened films are handled .

46. The red GBX-2 filter is recommended as a safelight in the darkroom because this filter transmits light only at the red end of the spectrum . Film handling should be limited between 5-8 minutes because film emulsion shows some sensitivity to light from a safelight with prolonged exposure .

47. Manual processing tanks Practical size of about 20cm×25 cm ( 8×10 inches). The tank should have hot and cold running water and a means of maintaining the temperature between 60 and 70 degree F. Consists of 1 master tank and 2 insert tank. Should be made of stainless steel which does not react with the processing solutions and is easy to clean.

48. Fig: Processing tank

49. Master tank Filled with circulating water. Should have a cover to reduce oxidation of the processing solutions, protect the developing film from accidental exposure to light and minimize evaporation of the processing solutions.

50. Insert tank Two, removable tanks Holds 3.8 L (1 gallon) of developer or fixer, placed within the outer, larger master tank. Developer solution is placed in the insert tank on the left side and fixer solution in the insert tank on the right side of the master tank. Water in master tank separates the two insert tanks.

51. Thermometer Used to determine the temperature of developing, fixing and washing solutions. It can be left in the water circulating through master tank to monitor its temperature. Thermometer used may contain alcohol or metal but they should not contain mercury because they could break and contaminate the processor or solutions.

52. Timer The x-ray film must be exposed to the processing chemicals for specific intervals. An interval timer is indispensable for controlling development and fixation times.

53. Drying racks Two or three drying racks can be mounted on a convenient wall for film hangers. Drip trays are placed underneath the racks to catch water that may run off the wet films. An electric fan can be used to circulate the air and speed drying the films but it should not be pointed directly at the films. Also, cabinet dryers are available that circulate warm air around the film and accelerate drying.

54. Film hangers Also known as processing hangers. Made up of stainless steel. Equipped with clips used to hold films during processing. Available in various sizes and can hold upto 20 intraoral films .

55. Fig : Film hangers

56. Processing methods 1.Manual processing method Time-temperature method Visual method Rapid processing method 2. Automatic method Monobath method Self developing films

57. Manual processing method : Sequence of steps in manual processing: Time-temperature method Replenish solutions Before processing check the solution level of developer and fixer. If the solution level is low, add fresh solution.

58. Stir solutions Use stirring rod or paddle This mixes chemicals and regularizes the temperature of the solution. Check the temperature of the developer solution. The optimal temperature for the developer is between 65°F to 70°F.

59. Mount films on hanger Turn on the safe light Remove the exposed film from its lightproof packet Hold the film only from their edges Clip the bare film to the hanger clip (1 film to a single clip)

60. Solution Temperature (in degree F) Developing time (in minute) 65°F 6 minute 68°F 5 minute 70°F 4.5 minute 72°F 4 minute 76°F 3 minute 80°F 2.5 minute Set timer Based on temperature of developer solution and the instruction of manufacturer, set the timer. A time temperature chart is used to determine the time

61. Develop Immerse the film hangers with the films into developer solution. Film must not contact one another or the sides of the processing tanks during development. Activate the timer, agitate mildly for 5 seconds to sweep air bubbles off the film to allow uniform contrast of developer.

62. Rinse Rinse the film by placing in the circulating water for 30 seconds. Fix Immerse the film hanger with film in the fixer solution for 10 minutes. Gently agitate it for 5 seconds every 30 seconds. This eliminates air bubbles and brings fresh fixer in touch with emulsion.

63. Wash and dry The films are then placed in running water for at least 10 minutes Dry the film in circulating, moderately warm air. If heated using drying cabinet, temperature should not exceed 120°F. Remove the dry radiograph from the film hanger and radiograph is now ready for examining.

64. Visual method In this method the exposed X ray film is immersed in developing solution for about 10 seconds and then removed and observed in safe light. If adequate image have been obtained then it is put for rinsing otherwise reinserted in developing solution till adequate image is obtained. Disadvantage: Objective in nature and doesn’t give consistent quality.

65. Rapid processing method Rapid processing solutions typically develop films in 15 seconds and fix them in 15 seconds at room temperature. They have the same general formulation as conventional processing solutions but often contain a higher concentration of hydroquinone . They also have a more alkaline pH than conventional solutions, which causes the emulsion to swell more, thus providing greater access to developer .

66. Although the resultant images may be satisfactory, they often do not achieve the same degree of contrast as films processed conventionally , and they may discolor over time if not fully washed . After viewing, rapidly processed films are placed in conventional fixing solution for 4 minutes and washed for 10 minutes. This improves the contrast and helps keep them stable in storage.

67. Changing solutions Under average conditions solutions may provide service of 3-4 weeks, as all processing solutions may deteriorate due to: Continuous use Exposure to air Eventual build up of reaction products Loss of image contrast and density indicates time to change processing solutions.

68. Automatic film processing Step in automatic processing are more or less same like the manual processing with exception of rinsing , between developing and fixing. This stage is omitted because excess developer is either drained or squeezed.

69. Although automatic processing has numerous advantages, the most important is the time saved. Depending on the equipment and the temperature of operation, an automatic processor requires only 4-6 minutes to develop, fix, wash and dry.

70. Many dental automatic processors have a light-shielded (daylight loading) compartment in which the operator can unwrap films and feed them into the machine, without working in the darkroom. However , special care must be taken to maintain infection control when using these daylight-loading compartments.

71. Another attractive feature of the automatic system is that the density and contrast of the radiographs tend to be consistent . However, because of the higher temperature of the developer and the artifacts caused by rollers, the quality of films processed automatically often is not as high as that of those carefully developed manually.

72. Mechanism Automatic processing cycle is same as manual processing except that the rollers squeeze off any excessive developing solution before passing the fill on the fixer ,thus eliminating the need for the washing between these two steps.

73. Automatic processors have an in-line arrangement typically consisting of a transport mechanism that picks up the unwrapped film and passes it through the developing, fixing, washing, and drying sections .

74. Fig : Components of the automatic processor

75. There are series of rollers which transport the films through various sections for each step in the operation. These sections are designed and positioned so that the film crosses over from one roller to the next, the operator may remove them independently for soaking, cleaning, and repairing.

76. Functions of rollers Moving the film through the developing solutions. Agitation of solution which contributes to the uniformity of processing. I n the developer, fixer, and water tanks the rollers press on the film emulsion, forcing some solution out of the emulsion. The emulsions rapidly fill again with solution, thus promoting solution exchange . Minimizes carryover of developer into the fixer tank.

77. The chemical compositions of the developer and fixer are modified to operate at higher temperatures than those used for manual processing and to meet the more rapid development, fixing, washing, and drying requirements of automatic processing. The fixer has an additional hardener that helps the emulsion withstand the rigors of the transport system. Poor quality fixers containing no hardener produce more film artifacts.

78. Successful operation of an automatic processor requires standardized procedures and regular maintainance . The processor and surrounding area should be kept clean so that no chemicals contaminate hands or films. The solution level and temperature should be checked each morning. Hands should be dry while handling films.

79. Self developing films Alternative to manual processing. The x ray film is present in sachet containing developer and fixer . Following exposure the developer can be pulled, releasing developer solution which is milked down toward the film and flow around it.

80. After 15 seconds fixer tab is pulled to release the fixer solution which similarly baths down the film. After fixing the used chemicals are discarded and film is rinsed thoroughly under running water for ten minutes.

81. Advantages No darkroom or processing equipments are required. Final radiograph is ready in about a minute and hence saves time.

82. Disadvantages Resultant image has poor quality. Image deteriorates rapidly with time as fixing is inadequate As there is no lead foil inside film packet patient receives more radiation dose. As these film packets are very flexible and they bend easily, these films are difficult to use with positioning holders.

83. Monobath method In this method developer and fixer are combined in one solution . Fixer is alkaline and does not neutralize the developer. It is injected into special waterproof film packet and the film is developed by rubbing film packet. There is no need of darkroom. It is advantageous for quick spot diagnosis and for root canal treatment.  

84. Management of radiographic wastes Although dental radiograph waste constitutes only a small potential hazard it should be discarded properly. The primary ingredient of concern in processing solution is the dissolved silver found in used fixer. Another material is lead foil found in film packets. Dental offices should consider using companies licenced to pick up waste materials.

85. Conclusion Correct processing of radiographs is a key factor in good radiography. Correct processing is not an expensive procedure; however an understanding of basic fundamentals is required to avoid unnecessary errors that may destroy the detail of radiographs. So the proper technique for film processing should be employed to produce a good diagnostic radiograph.

86. References ORAL RADIOLOGY Principles and Interpretation, Staurt C . White , Michael J . Pharoah Oral and Maxillofacial Radiology: A Diagnostic Approach David MacDonald Fundamentals of oral and maxillofacial radiology, Hubar, Jack Sean

87. Thank you