Dark room procedures

Dark room procedures

1. DARK ROOM PROCEDURES Presenter – Dr. Anuraj Moderator – Dr. C.N. Pradeep Kumar

2. WHAT IS A DARKROOM ? Enclosed area or chamber dimly lit by safelight (usually red) but otherwise intentionally lightproof room where films are handled and processed.

3. DARK ROOM LAYOUT A room should be set aside as a permanent dark room, ideally with a floor area of not less than 10sq. m. The room must be capable of being made completely lightproof. It should not be damp or subjected to extremes of temperature. Water and electrical outlets should be provided. Sufficient space to accommodate a dry bench , a wet bench and a sink. Too large room is as undesirable as small room. Should be near the x-ray examination area. Should be well ventilated. The wall should be constructed of solid concrete (15 cm thick), have a lead box inside to store boxes of unexposed films currently in use. The walls and roof should be painted by white or cream enamel as such a paint acts as a good reflecting surface for safe light. X-ray rotating warning light in hallway switched "on" signaling that x-ray machine is operating.

4. LOCATION Centrally located Serviced by hatches from the adjacent imaging room Away from damp or hot areas Accessible in terms of power and water supply Adjoining viewing room

5. SIZE Minimum floor area of 10 sq meter Ceiling height of 2.5 - 3 meter Size may be reduced depending upon the department needs

6. LIGHT PROOF The first requisite of a processing room is the exclusion of all external white light when radiographs are processed. Photosensitive crystals in film emulsions are extremely sensitive to visible light, and any light leaking around a door or window may fog and ruin the films. A door that can be locked to avoid accidental exposure of film to white light. Alternatively a light outside the door indicating that the darkroom is in use. When the white light in the darkroom is switched off, the indicating light outside automatically goes on

7. RADIATION PROTECTION Walls adjacent to the radiographic room should be shielded with correct thickness of the lead all the way to the ceiling In the interests of both darkroom staff and film material alike 1.6 mm lead is mostly used

8. FLOORS Non-porous flooring Non-slip flooring Chemical resistant Stain proof Durable & easy to maintain Light coloured (low-light working conditions) Asphalt tiles Porcelain tiles Clay tiles Plastic tiles may be used in the dry dark-rooms

9. WALLS/CEILING Light in colour to reflect as much light as possible onto the working surface Easy to wipe or clean Covered with chemical resistant materials Special paints, varnish, ceramic or plastic wall

10. VENTILATION AND HEATING Satisfactory working conditions for the staff Good film handling and storage conditions Efficient automatic processor performance Relative humidity is maintained at around 40-60 % Room temperature maintained between 18-20 degree celsius A minimum of 10 air changes per hour All of these conditions can be achieved by using a good air-conditioning system Alternatively, fairly satisfactory ventilation can be achieved by using an extractor fan sited higher than and diagonally opposite a second fan, the latter being so placed as to obtain fresh and filtered air from outside.

11. TYPE OF ENTRANCE SINGLE DOOR SYSTEM DOUBLE DOOR SYSTEM MAZE TYPE ENTRANCE LABYRINTH ROTATING DOOR SYSTEM

12. DARK ROOM ENTRANCE REVOLVING DOOR SINGLE DOOR

13. DOUBLE DOOR MAZE

14. MAZE TYPE ENTRANCE

15. ROTATING DOOR ENTRANCE

16. DARK ROOM ILLUMINATION WHITE LIGHTING SAFELIGHTING

17. WHITE LIGHTING For inspection & maintenance of cassettes & screens Cleaning of work surfaces Servicing of equipment Sited close to the ceiling Moderate in intensity (60w tungsten, 30w fluorescent ) Preferably centrally placed

18. SAFE LIGHTING DIRECT SAFE LIGHTING : Light from safe lamp directly falls onto the work surface Eg . Beehive safelamp Minimum distance of 1.2 m/ 4 feet from the working surface Best for loading & unloading areas

19. INDIRECT SAFE LIGHTING Directs the light towards the ceiling which reflects light back into the room Is intended to provide general illumination of the dark room Suspended atleast 2.1 m above floor level

20. SAFE LIGHT FILTERS Sheet of gelatin dyed to the appropriate colour and sandwiched between two sheets of glass for protection Used in conjunction with a 15 W lamp Extremes of heat and temperature deteriorates the filter gelatin Should be cleaned periodically

21. How Does A Safelight Work? When white light is passed through coloured filters, certain wavelengths (or colours ) are absorbed by the filters, whilst those wavelengths, which correspond to the colour of the filters will be transmitted . Making the correct selection of safelight filter (matching the filter to the film), means choosing a filter, which will transmit a colour to which the film is relatively unresponsive , whilst stopping all light to which the film is most sensitive.

22. WHICH COLOUR FILTER TO USE? X-ray films have the highest sensitivity to the blue-green part of the light spectrum . The X-ray film is less sensitive to light in the opposite region of the spectrum - i.e. the yellow and red region. It is obvious that the blue filter cannot be used, neither a green color filter as it is so close to the blue. Therefore safelights are safest when made with amber or red filters.

23. How Safe Is Safe Lighting? No safe lighting is completely safe; all films will become significantly fogged if exposed to safelights for long enough. This is because safelight filters are not perfect absorbers of the undesirable wavelengths and, in truth, all films have some sensitivity to all wavelengths. Thus, the intensity of illumination and the film-handling time must be kept to a minimum if significant fogging is not to occur .

24. Safelight illumination test Place a coin on a small piece of photo paper. Let it sit for 20 min. and develop the paper. If you see the outline of the coin, your safelight isn't safe If the safelight is not safe, you should do one of the following to correct the problem: 1. Replace the bulb with one of lower wattage 2. Raise the safelight lamp higher from working surface 3. Check the filter - may be cracked or broken

25. DARK ROOM EQUIPMENTS Automatic processor Manual process unit Processing chemicals Hangers for suspending film Cassette Film storage hopper Loading bench Cupboards

26. DARK ROOM EQUIPMENTS Film cassettes: A cassette is designed to hold the x-ray film and intensifying screens in close contact. The front face which is of aluminum or plastic, faces the tube while the other side have a sheet of lead to absorbed back-scatter screens and cassettes are of course made in various sizes to correspond with standard film sizes. Mounting intensifying screens in the cassette Intensifying screens should be never be loose but must be properly mounted into the cassette. Because certain adhesives interact with the screens it is advisable to use only the double-sided tape provided by the manufacturers. The care of cassettes Do not drop them on a hard floor Do not trap the edges of the screens when the cassette is closed Cassettes should be kept clean and there is always the danger of blood or urine leaking to the inside of the cassette. When a cassette must be placed in a dirty situation put it in a plastic bag.

27. Dry Bench The dry bench is where the cassettes are unloaded and recharged with fresh film. It must be impossible for splashes of developer to reach the dry bench surface. The top of the dry bench must be large enough to accommodate the largest cassette in use when opened out. The top surface should be either of wood or linoleum. Plastic laminates are not recommended because they hold static charges of electricity which can cause marks on films. It is usual to store film boxes, especially those in current use , beneath the dry bench , either in a cupboard ( protected if near an X-ray set ) or in a film hopper. Wet Bench The wet bench is where the processing of the films is carried out. The usual method is to use a set of  tanks holding developer ,rinse water and fixer , and a larger tank for washing the films.

28. DARK ROOM DRY BENCH SYSTEM

29. PROCESSING TANKS 1. MASTER TANK This tank serves as a water jacket to hold the insert tanks and is usually large enough to provide space between insert tanks for rinsing and washing of films. The water assists in maintaining the same / constant temperature in the insert tanks. 2. INSERT TANKS These are removable containers for the individual processing solutions - (developer and fixer), and are spaced in the master tank

30. MANUAL PROCESS UNIT IN PK TB HOSPITAL

31. AN AUTOMATIC PROCESSOR

32. AUTOMATIC PROCESSOR

33. PROCESSING CHEMICALS

34.                                          Hangers used for suspending films during processing

35. CASSETTES

36. FILM BIN FILMS 8 X 10 10 X 12 11 X 14 14 X 17 TYPICAL DARK ROOM FILM BIN SLOTS OF DIFFERENT SIZES

37. 14 X 17 11 X 14 10 X 12 8 X 10 7 X 17 6 X 12 14 X 36 35 X 43 28 X 35 25 X 30 20 X 25 18 X 43 15 X 30 35 X 91 RADIOGRAPHIC FILM SIZES

38. Film Processing

39. RADIOGRAPHIC FILM

40. Gurney Mott hypothesis This process repeats.

41. Chemical sensitization Chemical sensitization of the crystals are produced by adding allylthiourea , a sulfur containing compound to the emulsion , which reacts with silver halide to form silver sulfide .

42. Sensitivity Speck This Silver Sulphide is usually located on surface of the crystals and is referred as “ sensitivity speck ”.

43. Point defect in cubic lattice. Sensitivity speck by Silver sulfide The sensitivity speck traps electron and form latent image .

44. The film is then passes through the following four steps Developing Fixing Washing Drying

45. CONSTITUENTS OF DEVELOPING SOLUTION

46. Development It is the first stage in processing of the radiograph. Amplifies latent image by 100,000,000 ! The primary purpose : convert the invisible latent image into visible form. Processing initiated at latent image speck

47. These are the reducing agents , which carry out the primary function of supplying the electrons that convert the exposed silver halide grains to silver. Characteristics : Selectivity High activity Should be resistant to bromide ions in the solution . Developing Agents

48. 1.DEVELOPING AGENTS Hydroquinone + phenidone / metol Hydoquinone (developer) +silver ions  quinone ( oxidised develper ) + silver atoms + hydrogen ions Phenidone (developer)+silver ions  oxidised developer+silver atoms+hydrogen atoms

49. Advantages of PQ developers 1. Tolerant of increase in bromine ion concentration. 2. High selectivity and low chemical fog. 3. Adequate activity even in low concentrations. 4. Available in liquid concentrate form. 5. Fast acting 6. Adequate contrast 7. Super additive effect

50. SUPER ADDITIVE EFFECT

51. ACCELERATOR/ACTIVATOR/BUFFERING AGENT Alkaline medium for the action of PQ-accelerates the developing process KCO 3 or KOH Ideal range of pH: 9.8-11.4 RESTRAINER/Anti- foggant It reduces converting unexposed AgX to Ag and thus prevent chemical fogging . KBr , benzotriazole (used with PQ developer) DEVELOPING SOLUTION

52. PRESERVATIVE It reduces the oxidation of developing agents. Eg : Potassium sulphite HARDENER It controls gelatin swelling to minimize risk of physical damage. Eg:Glutaraldehyde DEVELOPING SOLUTION

53. SEQUESTERING AGENT Prevents the precipitation of insoluble mineral salts which occur in hard water areas EDTA containing compounds are used SOLVENT Carrying medium for dissolving the developer constituents Softens the film emulsion gelatin MC used : Tap water DEVELOPING SOLUTION

54. Temperature of the developing solution Total time of the development An adequate combination of both is important for complete development FACTORS AFFECTING DEVELOPMENT

55. Optimum temperature is 20- 22 o C Below 16 o C, action of hydroquinone ceases Radiograph lacks contrast and density Can be compensated by increasing the developing time. Above 24 o C (too warm) emulsion softens. Chemical fog results TEMPERATURE FOR DEVELOPMENT

56. During development not all the silver halides are reduced. Only 40% get reduced The remaining silver halides greatly impairs the usefulness and permanence of the developed radiograph and hence have to be removed. STAGE 2:FIXING

57. It has four major functions Stop any further development Makes the solution more acidic Remove the unexposed AgX from the emulsion Convert it to soluble compounds and remove it Makes the image chemically stable and no longer photosensitive Completes the process of hardening of emulsion Minimizes water absorption and reduces drying time FIXATION

58. 1. Solvent 2. Fixing agent 3. Acid 4. Hardener 5. Buffer 6. Preservative 7. Anti- sludging agent   Constituents of the fixing solution :

59. 1 .SOLVENT Water 2 . FIXING AGENT 2 agents: Cyanides Poisonous Not generally used. Thiosulfates - Sodium and Ammonium Salt (more active ) – called Hypo . AgBr + sod. Thiosulfate  Ag thiosulfate complex + NaBr (water soluble)

60. Acid: Prevents dichoric fog by inhibiting developing agents. Provides a suitable environment for the hardening agents in the fixer. Acetic acid is used usually at a pH of 4-4.5. Hardener : Reduces drying time and prevents physical damage. Aluminium chloride and aluminium sulfate (or Chromium compounds) are used commonly . Buffer : Prevents sulphurization . Neutralizes the developer Sodium acetate is commonly used in conjunction with acetic acid

61. Preservative : Retards decomposition of thiosulphates Sodium sulphate is commonly used Antisludging agent : Boric acid is commonly used and this prevents sludging of insoluble aluminium compounds in the hardener.

62. Purpose of washing is to remove fixing solution from the surface of the film. If the film is not properly washed, it will show a brown staining caused by thiosulfate (fixing agent that remains in the emulsions). The process by which washing works is diffusion . Tap Water is mainly used STAGE 3 : WASHING

63. The drying medium is dry air of low humidity , which accelerates the evaporation process and reduces drying time. Film drying box Heating element with a circulating fan. It can dry in 15 minutes. Film will dry properly if hung in air for a longer period (1+ hours). STAGE 4 : DRYING

64. The longer the film spends in the fixer, the longer the wash time needed This is a 1:2:3 ratio of developer to fixer to wash

65. TYPES OF FILM PROCESSING A UTOMATIC MANUAL Unloading the film Inserting into processor Unloading the film Loading the film onto a hanger Development Fixing Washing Drying

66. AUTOMATIC PROCESSOR Tanks For Developer solution Fixer solution Wash tank for water During a 90s processing cycle Developer------ 26s Fixer ----- 15s Wash ----- 15s Drier ------ 24s Travel time----- 10s

67. MANUAL PROCESSING

68. MANUAL PROCESSING DEVELOPING It is done by time – temperature technique Here film is immersed in developer for 4 minutes Temperature is maintained at 20 C At intervals with in 4 minutes film is examined under safelights If image seems to lack expected density at 4 minutes, development is continued

69. MANUAL PROCESSING RINSING Purpose is to slow the action of developer and to remove it from the surfaces of the film, done by a plain rinse bath . To stop the action of developer, done by acid stop bath. FIXING After rinsing, the film is immersed in fixer solution Fixing time can be up to 5 minutes

70. MANUAL PROCESSING WASHING Immerse the film in large tank or in a series of tanks through which water is kept flowing. Time duration:- 20 – 30 minutes DRYING Hot air drying cupboards or by rapid drier machines . Temperature may vary from 40-50 C

71. Developing – formation of the image Fixing – stopping of development, permanent fixing of image on film Washing – removal of residual fixer Drying – warm air blowing over film 4 Steps of Processing

72. COMPARISON DEVELOPING TEMP 20 c FIXING TEMP 20 C WASHING TEMP 20 C DRYING TEMP 43 C DEVELOPING TIME 3-5 MIN FIXING TIME 2-10MIN WASHING TIME 15-30MIN DRYING TIME 15-20MIN AUTOMATIC 35 C 35 C 35 C 57 C 25s 15s 15s 20s MANUAL

73. CLEANING THE PROCESSING TANKS The action between the mineral salts in the water and carbonate in the developing solutions produces a deposit on the inside wall of the processing tanks. A commercially prepared stainless steel tank cleaner can be used to remove these deposits. Or simply brush thoroughly with a brush and water.

74. The developing solution should be tightly covered when not in use to reduce oxidation. The solution should be discarded and replaced after three months of use because oxidation and accumulation of gelatin sludge and other impurities will cause poor development. As the solution weakens it first turns yellow, then brown. When it turns brown, indicating exhaustion, it should be replaced. Few important points to be kept in mind

75. Christensen’s physics of diagnostic radiology REFERENCES

76. Thank You!!!