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Dark Room Construction

Tarique Ajij
Tarique Ajij

This document discusses the proper construction, equipment, and safety procedures for a radiology dark room. It outlines important considerations for the location, size, ventilation, lighting, entrance types, and hazards associated with a dark room. Key pieces of equipment like cassettes, film hangers, and processing chemicals and their uses are described. Common problems that can occur with screen film radiography like crossover exposure, cassette artifacts, and dirty/damaged screens are also reviewed.

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DARK ROOM & PITFALLS OF IMAGING Dr.Tarique Ajij Junior Resident, Department of Radio- Diagnosis, Medical College, Kolkata
DARK ROOM CONSTRUCTION A Dark room is a room, from which normal light is excluded. It is made completely dark to allow the processing of light sensitive photographic materials.
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
HATCHES Hatches are designed to transfer film cassettes to and from the dark room without radiation light entering It consist of metallic structures with a lead lining to provide x ray shielding. They are typically wall mounted and include automatic interlocks that close one door when other is opened. It is also used for the temporary storage of loaded cassettes.
SIZE Minimum floor area of 10 sq meter Ceiling height of 2.5 - 3 meter Size may be reduced depending upon the department needs
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
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
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
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.
TYPE OF ENTRANCE SINGLE DOOR SYSTEM DOUBLE DOOR SYSTEM MAZE TYPE ENTRANCE LABYRINTH ROTATING DOOR SYSTEM
ROTATING DOOR SYSTEM Most efficient but most expensive type. Composed of two black cylinders. The outer is fixed. Inner is the revolving door with only one opening.
FIRE SAFETY Ideally, all darkrooms should be provided with an alternative exit, which should be indicated clearly and left unobstructed at all times
DARK ROOM ILLUMINATION WHITE LIGHTING SAFELIGHTING
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 More than one switch preferable Identification of respective switches is important
SAFE LIGHTING DIRECT SAFE LIGHTING Light from safe lamp directly falls onto the work surface Eg. Beehive safelamp Minimum distance of 1.2 m from the working surface Best for loading & unloading areas
SAFE LIGHTING 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
SAFE LAMP FOR BOTH DIRECT & INDIRECT ILLUMINATION
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 25 W lamp Extremes of heat and temperature deteriorates the filter gelatin Should be cleaned periodically
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.
SPECTRUM TRANSMISSION GRAPH: Manufacturers produce graphs for their safelights called spectral transmission or filter transmission graphs. Their purpose is to indicate that part of the visible spectrum, which will be transmitted by the filter, and so aid the radiographer in matching the appropriate filter to the type of film in use. Panchromatic film presents special problems, since it will have colour sensitivity extending as far as the red end of the spectrum. It is thus advisable to process such film in complete darkness.
SPECTRAL TRANSMISSION GRAPH MONOCHROMATIC FILM ORTHOCHROMATIC FILM
IN SHORT!! AMBER BLUE LIGHT SENSITIVE FILM(400-450nm) REDGREEN LIGHT SENSITIVE FILM ORTHOCHROMATIC(500- 550nm) TOTAL DARKNESS FOR PANCHROMATIC FILM (1200nm)
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.
EFFECT OF EXCESSIVE SAFE LIGHT EXPOSURE Two principal features occur when film is exposed to safelights for too long: 1.An increase in gross fog; 2.An overall loss of contrast.
DARK ROOM EQUIPMENTS Automatic processor Manual process unit Processing chemicals Hangers for suspending film Cassette Film storage hopper Loading bench Cupboards
AN AUTOMATIC PROCESSOR
MANUAL PROCESS UNIT
PROCESSING TANKS FOUR tanks in the processing procedure. DEVELOPER RINZING FIXER WASHING
PROCESSING TANKS Universally used tank sizes: 1 gallon 2 gallon 3 gallon 5 gallon 10 gallon 1 GALLON=4.5 LITRES Processing tanks are made up of stainless steel to avoid erosion. The width of the tank may vary according to the capacity of the tank.
PROCESSING CHEMICALS
HANGERS USED FOR SUSPENDING FILMS DURING PROCESSING A film hanger is a instrument or device for holding radiographic film during processing procedure. Available in various sizes. Made up of stainless steel. Three types of hangers 1. CLIP TYPE 2. CHANNEL TYPE 3. SPRING TYPE
CASSETTES A radiographic film cassette is a rectangle or square plastic or metallic container used to hold x ray film (exposed or unexposed) and intensifying screens in close and uniform contact with one another.
CASSETTE SIZE DIFFERENT CASSETTE SIZES 17 x 14 inches 15 x 12 14 x 14 12 x 12 12 x 10 10 x 8 12 x 6 (OPG)
USES OF CASSETTES 1. Hold intensifying screen and protect them from damage. 2. Exclude all light from entering the cassette and fogging the film. 3. Maintain a close and uniform contact between the screen and film. 4. Exclude dust and dirt from the sensitive films. 5. Act as a medium from exposure up to further processing of film.
FILM HOPPER FOR THE STORAGE OF UNEXPOSED FILMS Film racks are used to keep the film boxes. It is very important that film boxes are always kept vertically. Not horizontally. When we keep horizontally pressure on the film boxes may produce artifacts.
DARK ROOM DRY BENCH SYSTEM
LAYOUT OF A TYPICAL DARK ROOM : AMPLE STORAGE & WORK SURFACES
HEALTH AND SAFETY IN THE PROCESSING AREA ELECTRICAL SAFETY GENERAL SAFETY CHEMICAL SAFETY
ELECTRICAL SAFETTY All electrical equipments to be sited well away from sinks & manual processing units Adequate earthing of all electrical appliances No trailing cables from appliances Pull-cord switching for lights
GENERAL SAFETY MEASURES The maximum level of safe lighting consistent with film sensitivity Adequate ventilation Second exits for fire safety
CHEMICAL HAZARDS Processing chemicals contain many toxic substances and must always be handled with care. Staff should always be aware of the harmful effects of exposure to the chemistry its fumes through inhalation, ingestion or skin contact. All staff involved with the handling of film chemistry should be regularly advised to read product labels and mixing instructions before handling solutions. Safety glasses, facemask, rubber gloves and plastic apron should be available within the processing area for each procedure.
PITFALLS OF SCREEN FILM RADIOGRAPHY
CROSSOVER EXPOSURE OR PRINT THROUGH EXPOSURE Light from one screen exposes opposite emulsion Top Screen Bottom Screen Bottom Emulsion Top Emulsion Film X-Ray
CROSSOVER caused by incomplete absorption of light by adjacent emulsion poorer resolution light travels further, spreads more can account for up to 40% of total exposure X-Ray
CROSSOVER REDUCTION Increase the light absorption in the silver halide grains of the film emulsion use light-absorbing dye on film base can reduce crossover exposure ~ 13% also reduces system speed by up to 40% X-Ray
CROSSOVER REDUCTION BY INCREASING LIGHT ABSORPTION Match screen light emission to silver halide natural sensitivity 1. Yttrium tantalate phosphor intensifying screens 2. Adding a dye, matched to light emission of the screen, to the emulsion reduces crossover without decreasing speed use flat film grains present larger surface to incoming light Large surface-area-to-volume ratio absorb more light photons Kodak T-Mat film cuts crossover ~ X2
EXAMPLES OF SCREEN PROBLEMS
CASSETTE ARTIFACTS This cassette popped partly open.
CASSETTE ARTIFACTS Dirty screens will appear as white spots on the film. This film also has some static electricity artifacts.
CASSETTE ARTIFACT DIRTY SCREENS Dirty or damaged screens will cause white spots on the image.
DIRTY OR DAMAGED SCREENS Dirty or damaged screen will cause white spots on the image.
DIRTY & DAMAGED SCREENS The white spots on this film are the result of damaged or worn out screens. Never use alcohol or detergents to clean screens.
POOR SCREEN CONTACT There is a loss of detail in the thoracic and lumbar spine due to poor screen contact. This was a new cassette.
Dark Room Construction

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Dark Room Construction

  • 1. DARK ROOM & PITFALLS OF IMAGING Dr.Tarique Ajij Junior Resident, Department of Radio- Diagnosis, Medical College, Kolkata
  • 2. DARK ROOM CONSTRUCTION A Dark room is a room, from which normal light is excluded. It is made completely dark to allow the processing of light sensitive photographic materials.
  • 3. 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
  • 4. HATCHES Hatches are designed to transfer film cassettes to and from the dark room without radiation light entering It consist of metallic structures with a lead lining to provide x ray shielding. They are typically wall mounted and include automatic interlocks that close one door when other is opened. It is also used for the temporary storage of loaded cassettes.
  • 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. 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
  • 7. 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
  • 8. 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
  • 9. 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.
  • 10. TYPE OF ENTRANCE SINGLE DOOR SYSTEM DOUBLE DOOR SYSTEM MAZE TYPE ENTRANCE LABYRINTH ROTATING DOOR SYSTEM
  • 11. ROTATING DOOR SYSTEM Most efficient but most expensive type. Composed of two black cylinders. The outer is fixed. Inner is the revolving door with only one opening.
  • 12. FIRE SAFETY Ideally, all darkrooms should be provided with an alternative exit, which should be indicated clearly and left unobstructed at all times
  • 13. DARK ROOM ILLUMINATION WHITE LIGHTING SAFELIGHTING
  • 14. 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 More than one switch preferable Identification of respective switches is important
  • 15. SAFE LIGHTING DIRECT SAFE LIGHTING Light from safe lamp directly falls onto the work surface Eg. Beehive safelamp Minimum distance of 1.2 m from the working surface Best for loading & unloading areas
  • 16. SAFE LIGHTING 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
  • 17. SAFE LAMP FOR BOTH DIRECT & INDIRECT ILLUMINATION
  • 18. 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 25 W lamp Extremes of heat and temperature deteriorates the filter gelatin Should be cleaned periodically
  • 19. 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.
  • 20. SPECTRUM TRANSMISSION GRAPH: Manufacturers produce graphs for their safelights called spectral transmission or filter transmission graphs. Their purpose is to indicate that part of the visible spectrum, which will be transmitted by the filter, and so aid the radiographer in matching the appropriate filter to the type of film in use. Panchromatic film presents special problems, since it will have colour sensitivity extending as far as the red end of the spectrum. It is thus advisable to process such film in complete darkness.
  • 21. SPECTRAL TRANSMISSION GRAPH MONOCHROMATIC FILM ORTHOCHROMATIC FILM
  • 22. IN SHORT!! AMBER BLUE LIGHT SENSITIVE FILM(400-450nm) REDGREEN LIGHT SENSITIVE FILM ORTHOCHROMATIC(500- 550nm) TOTAL DARKNESS FOR PANCHROMATIC FILM (1200nm)
  • 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. EFFECT OF EXCESSIVE SAFE LIGHT EXPOSURE Two principal features occur when film is exposed to safelights for too long: 1.An increase in gross fog; 2.An overall loss of contrast.
  • 25. DARK ROOM EQUIPMENTS Automatic processor Manual process unit Processing chemicals Hangers for suspending film Cassette Film storage hopper Loading bench Cupboards
  • 28. PROCESSING TANKS FOUR tanks in the processing procedure. DEVELOPER RINZING FIXER WASHING
  • 29. PROCESSING TANKS Universally used tank sizes: 1 gallon 2 gallon 3 gallon 5 gallon 10 gallon 1 GALLON=4.5 LITRES Processing tanks are made up of stainless steel to avoid erosion. The width of the tank may vary according to the capacity of the tank.
  • 31. HANGERS USED FOR SUSPENDING FILMS DURING PROCESSING A film hanger is a instrument or device for holding radiographic film during processing procedure. Available in various sizes. Made up of stainless steel. Three types of hangers 1. CLIP TYPE 2. CHANNEL TYPE 3. SPRING TYPE
  • 32. CASSETTES A radiographic film cassette is a rectangle or square plastic or metallic container used to hold x ray film (exposed or unexposed) and intensifying screens in close and uniform contact with one another.
  • 33. CASSETTE SIZE DIFFERENT CASSETTE SIZES 17 x 14 inches 15 x 12 14 x 14 12 x 12 12 x 10 10 x 8 12 x 6 (OPG)
  • 34. USES OF CASSETTES 1. Hold intensifying screen and protect them from damage. 2. Exclude all light from entering the cassette and fogging the film. 3. Maintain a close and uniform contact between the screen and film. 4. Exclude dust and dirt from the sensitive films. 5. Act as a medium from exposure up to further processing of film.
  • 35. FILM HOPPER FOR THE STORAGE OF UNEXPOSED FILMS Film racks are used to keep the film boxes. It is very important that film boxes are always kept vertically. Not horizontally. When we keep horizontally pressure on the film boxes may produce artifacts.
  • 36. DARK ROOM DRY BENCH SYSTEM
  • 37. LAYOUT OF A TYPICAL DARK ROOM : AMPLE STORAGE & WORK SURFACES
  • 38. HEALTH AND SAFETY IN THE PROCESSING AREA ELECTRICAL SAFETY GENERAL SAFETY CHEMICAL SAFETY
  • 39. ELECTRICAL SAFETTY All electrical equipments to be sited well away from sinks & manual processing units Adequate earthing of all electrical appliances No trailing cables from appliances Pull-cord switching for lights
  • 40. GENERAL SAFETY MEASURES The maximum level of safe lighting consistent with film sensitivity Adequate ventilation Second exits for fire safety
  • 41. CHEMICAL HAZARDS Processing chemicals contain many toxic substances and must always be handled with care. Staff should always be aware of the harmful effects of exposure to the chemistry its fumes through inhalation, ingestion or skin contact. All staff involved with the handling of film chemistry should be regularly advised to read product labels and mixing instructions before handling solutions. Safety glasses, facemask, rubber gloves and plastic apron should be available within the processing area for each procedure.
  • 42. PITFALLS OF SCREEN FILM RADIOGRAPHY
  • 43. CROSSOVER EXPOSURE OR PRINT THROUGH EXPOSURE Light from one screen exposes opposite emulsion Top Screen Bottom Screen Bottom Emulsion Top Emulsion Film X-Ray
  • 44. CROSSOVER caused by incomplete absorption of light by adjacent emulsion poorer resolution light travels further, spreads more can account for up to 40% of total exposure X-Ray
  • 45. CROSSOVER REDUCTION Increase the light absorption in the silver halide grains of the film emulsion use light-absorbing dye on film base can reduce crossover exposure ~ 13% also reduces system speed by up to 40% X-Ray
  • 46. CROSSOVER REDUCTION BY INCREASING LIGHT ABSORPTION Match screen light emission to silver halide natural sensitivity 1. Yttrium tantalate phosphor intensifying screens 2. Adding a dye, matched to light emission of the screen, to the emulsion reduces crossover without decreasing speed use flat film grains present larger surface to incoming light Large surface-area-to-volume ratio absorb more light photons Kodak T-Mat film cuts crossover ~ X2
  • 47. EXAMPLES OF SCREEN PROBLEMS
  • 48. CASSETTE ARTIFACTS This cassette popped partly open.
  • 49. CASSETTE ARTIFACTS Dirty screens will appear as white spots on the film. This film also has some static electricity artifacts.
  • 50. CASSETTE ARTIFACT DIRTY SCREENS Dirty or damaged screens will cause white spots on the image.
  • 51. DIRTY OR DAMAGED SCREENS Dirty or damaged screen will cause white spots on the image.
  • 52. DIRTY & DAMAGED SCREENS The white spots on this film are the result of damaged or worn out screens. Never use alcohol or detergents to clean screens.
  • 53. POOR SCREEN CONTACT There is a loss of detail in the thoracic and lumbar spine due to poor screen contact. This was a new cassette.