4. TYPICAL DARK ROOM
4
Darkroom layout
The darkroom should preferably be
divided into a dry side and a wet
side. The dry side
will be used for loading and
emptying cassettes, fitting films into
developing frames and
so on - in short, for all the work that
does not allow dampness.
On the wet side, the films will be
processed in the various tanks of
chemical solution.
For efficient working, and to ensure
uniform quality, there should be
automatic control
of the temperature of the solutions.
5. DARK ROOM
• Darkroom layout
• The darkroom should preferably be divided into a
dry side and a wet side. The dry side will be used
for loading and emptying cassettes, fitting films into
developing frames and so on - in short, for all the
work that does not allow dampness.
• On the wet side, the films will be processed in the
various tanks of chemical solution.
• For efficient working, and to ensure uniform quality,
there should be automatic control of the
temperature of the solutions.
5
7. Dark Room
• Light tight room to allow opining the x- ray films
safely without exposure to light
• Supplied with a safe light (red or orange) to permit
unwrapping the films in otherwise total darkness
• Should be covered with acid resistant, washable
benches
• Well ventilated, convenient, and clean.
• Supplied with disinfectants to disinfect films and
other materials
7
9. 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
10. 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
11. 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
13. 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
14. 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.
15. 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.
21. SOME FILM BASICS -EMULSION LAYER
21
Has 2 principle components –
I. Silver halide grains
II. Vehicle matrix
It consists of a homogeneous mixture of gelatin and silver
halide crystals.
In typical emulsion 90 to 99% is AgBr and about 1 to 10% AgI .
Emulsion
Layers
The presence of AgI produce an emulsion of much
sensitivity than a pure AgBr emulsion.
It also contains traces of sulfur (ALLYLTHIOUREA).
21
22. 22
Silver halide in a emulsion is in the form of small crystals.
Silver halide crystals may be tabular, globular, polyhedral,
or irregular in shape.
Crystal size might vary from
1.0 –1.5 microns in diameter
with about 6.3 x 1010 grains
per centimeter of emulsion.
22
23. • Granular
• Tabular
Scanning electron micrographs
of emulsion comparing flat
tabular silver bromide crystals
of InSight film
Scanning electron micrographs of
emulsion comparing with
globular silver halide crystals of
Ultra-Speed film .
23
24. Chemical sensitization
• Chemical sensitization of the crystals are
produced by adding allythiourea, a sulfur
containing compound to the emulsion , which
reacts with silver halide to form silver sulfide.
26. Sensitivity Speck
• This Silver Sulphide is
usually located on
surface of the crystals
and is referred as
“sensitivity speck”.
27. Point defect in
cubic lattice.
Sensitivity
speck by Silver
sulfide
The sensitivity speck traps electron and form latent image.
28. The Latent Image
• Remnant radiation interacts with the silver
halide crystals
• Mainly by the photoelectric interaction
• The energy deposited into the film is in the
same
pattern as the subject that was exposed
to radiation
• This invisible image is known as the latent
image
• A latent image on photographic
(radiographic) film is an invisible image
produced by the exposure of the film to light
(radiation).
29. The Manifest Image
• By chemically processing the latent image it is
made visible
• Certain chemicals permanently fixate the
image onto the film
30.
31. Formation of Latent Image
• Metallic silver is black, so it is this
metallic silver that produces black areas
on a developed films.
• Exposure of silver-iodo-bromide grains to
light photons emitted by screen / direct x-ray
exposure initiates the formation of atomic
silver to form a visible pattern.
34. • Negative Bromine
Ions lose electron to
form bromine Atoms
leaves the crystal
and diffuses into
Gelatin.
35. Latent Image Formation: Gurney-Mott
Light photon absorbed by/ejects Br
electron
Electron trapped at sensitivity
speck
Neg electron attracts interstitial
Ag+ ion
Ag+ and e- combine to form neutral
(black) Ag
If >6-10 Ag0
accumulate at speck, it becomes a
latent image center: ie, it is
developable.
36. 36
Film developing is the process by which a latent image, is converted into
a visible image. The crystals in the emulsion - carriers of the silver traces
forming the latent image - are transformed into metallic silver by selective
reduction as a result of which the visible image is created. The
development procedure must be carried out carefully to achieve this and
guarantee successful archiving over a longer period. Manual developing is
a laborious process that must be carried out meticulously in order to get
the high quality results.
For increased efficiency and uniform quality, X-ray films are more
commonly processed automatically.
The manual process is, however, still frequently applied. It will therefore be
useful to describe manual processing in this chapter and so become
familiar with the developing process.
37. The Latent Image
• This process is not well understood and is the
subject of considerable research.
• The following is the Gurney-Mott theory.
37
38. Producing the Latent Image
A Radiation interaction
releases electrons.
B Electrons migrate to the
sensitivity center.
C At the sensitivity
center, atomic silver is
formed by attracting an
interstitial silver ion.
38
39. Producing the Latent Image
D The process is repeated
many times resulting in
the build up of silver
atoms.
E The remaining silver
halide is converted to
silver during processing.
39
40. Producing the Latent Image
F The resulting silver
grain is formed.
Silver halide that is not
irradiated remain
inactive. The irradiated
and non-irradiated
silver halide produces
the latent image.
40
42. 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
43. Chemistry Of Developer
• Development is a process of chemical reduction.
• The reduction is achieved by the developer donating
electrons to silver ions in the exposed silver bromide
and iodide grains converting them to atoms of metallic
silver.
Ag+ + electron Ag
• The mode of action of developer is not fully understood
but the existence of electric charge barriers around the
halide grains is thought to be involved.
44. • Both exposed and unexposed
silver bromide grains are
surrounded by a negative
charge barrier of bromide
ions created by the excess of
potassium bromide employed
bromide during
in the synthesis of silver
the
manufacture of emulsion.
• The charge barrier protects
the silver
attack by
bromide from
electrons in the
developer solution.
Charge Barriers
UNEXPOSED GRAIN
45. Charge Barriers
EXPOSED GRAIN
• Exposed silver bromide grains
possess a weakness in the
charge barrier caused by the
presence of neutral silver
atoms, which have collected
at the sensitivity speck.
• This development center
developer to penetrate
enables electrons from the
the
grain and reduce all its silver
ions to metallic silver.
46. Development
• Silver atoms at
latent image
center act as
catalyst
• Grain either
develops entirely
or not at all
48. Constituents Of The Developer
• Replenisher solution:
– This consists of:
Solvent Developing agents
Accelerator
Buffers
Restrainer Preservative
Hardener Sequestering agents
49. 1. Solvent
Water is the solvent commonly used in replenisher
solution.
– This also controls developer activity by diluting its effects.
– It has a softening effect on the gelatin, thus allowing the
developing chemicals to penetrate the emulsion and act on the
silver halides.
– The presence of calcium salts in the water (hard water) may
form a chalky deposit or scum on the surface of the film.
– More serious would be contamination of the solvent with
dissolved metals like copper and iron. The presence of only a
fewer parts per million of copper could cause chemical fogging.
– In practice, such effects are extremely rare.
50. 2. Developing Agents
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:
1. Selectivity
2. High activity: Selectivity and activity tend to
be antagonistic properties.
An agent with high activity generally has low selectivity and vice versa.
3. Should be resistant to bromide ions in the solution.
51. • No single agent satisfies all these requirements Modern
X-ray developers use a combination of 2 developing
agents phenidone and hydroquinone known as PQ
developer.
• Phenidone is a quick acting reducing agent capable of
developing all exposed silver halide grains. However, its
selectivity is low and if used alone would result in high
fog levels.
• Hydroquinone requires a strong alkaline medium for its
action. This is more selective than phenidone but slower
in onset of action. Once its action has begun the
development proceeds vigorously although lightly
exposed grains are not affected by hydroquinone.
– Hydroquinone and Phenidone – High Contrast
– Metol – High Speed/Low Contrast/Fine grain
52. Reaction
• Involves donation of Electron by developing agent
to form metallic Silver by Silver Ion (with
inactivation of developing agent and liberation of
hydrogen ions )
Alkaline
Medium
53. • 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
55. Manual Film Processing
• Unwrap the exposed film (in the dark room)
• Clip to a hanger
• Immerse the film in the developer for 4.5 min at 20
C. Agitate
• Wash
• Immerse film in the fixer for 8 minutes at 20 C
• Wash
• Dry
55
o
o
67. Automatic Film Processing
• Unwrap the exposed film (in the dark room) or in a
day light loader
• Insert the film in the loading slot
• Receive the film dry from the film exit slot
67
70. 4 Steps of Processing
• 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
71. Systems of the Automatic
Processor
1. The Film Feed Section
2. Transport System
3. Temperature Control
System
4. Recirculation System
5. Replenishment System
6. Dryer System
7. Electrical System
72. 1. The Film Feed Section
• As a film is fed to the processor,
so the cycle of events listed
below is initiated:
Drive motor energized (to turn
the rollers).
Safelight above feed tray
extinguished.
Developer and fixer replenisher
pumped into tanks.
Drier heater energized.
Wash water flow rate boosted.
Film signal delay timer activated
(audible signal which will sound
1-3s after the trailing edge of
the film has passed the entry
rollers, to let the operator know
that the next film can be fed to
the processor).
73. 2. The Film Transport Section
• A system of rollers that
moves the film through the
developer, fixer, washing and
drying sections of the
processor.
• Also acts as a squeegee
action to remove excess
chemicals from the film.
74. Make up of the Transport System
1. Entrance roller or detector roller
2. Vertical or Deep racks (transport racks)
3. Crossover assembly
4. Squeegee assembly
75. 1. Entrance Roller Or Detector
Roller
• Entrance rollers grab film
and draw it into developer
• Entrance rollers separate
slightly, film passes
between rollers activating
microswitch controlling
replenishment of chemicals
• When film is completely in
developer tank, bell ring or
light flicks on – safe to turn
on light
76. 2. Vertical or Deep racks (transport racks)
• Moves film into and
through solutions
and dryer
• Uses a turn around
assembly at the
bottom of the tank
to turn film direction
upward.
77. 3. Crossover Assembly
• Moves film from
developer to fixer
tank and from the
fixer to the wash tank
• Forces solutions from
film back into the
tank it is coming
from.
78. 4. Squeegee Assembly
• Moves the film from
the wash tank to the
dryer
• Squeegee action
removes excess water
from the film.
80. Water System
• 2 functions:
– Washing the film
– Temperature control
81. Washing
• Removes the last traces of
processing chemicals and
prevents fading or
discoloration.
• This enables long term
storage capability
82. 3. Temperature Control System
• Maintains
developer, fixer &
dryer temperature
Processing Temperatures
Developer 35° C
Fixer 35 ° C
Wash 32-35 ° C
Dryer 57 ° C
83. 4. Circulation or Recirculation or
Filtration System
• Agitates developer solution
• Removes reaction particles by the use of a
filtration system
• Helps stabilize developer temperature.
– Agitation and circulation
– Agitation keeps solutions in contact with a heater
element in the bottom of the tank and prevents layering
of chemicals
– Maintains developer temperature
– Heating element is controlled by a thermostat
84. Recirculation System
• Controlled by recirculation pumps that agitate
solutions to keep them mixed to maintain constant
temperature
• Circulation of water required to wash residual fixer
(12 litres per minute)
85. 5. Replenishment System
• Fixer & developer levels drop as films
processed
• System replaces lost chemicals
• Microswitch of entrance rollers starts
replenishment pump – stops when film exits
entrance rollers
86. Replenishment System
• Typical replenishment rates: 60-70 mls of developer, and 100-110
ml of fixer for every 14 inches of x-ray film (per 35 x 43cm
crosswise film)
87. Types of Replenishment
• Volume Replenishment
– A volume of chemicals are replaced for each film
that is processed.
• Flood Replenishment
– Periodically replenishes chemicals regardless of
the number of films processed.
88. 6. Dryer System
• Dries the film before its removal for viewing
• If not dry, difficult to hang on viewing box
• Consists of blower, ventilation ducts, vented
dryer tubes & exhaust system
• Blower draws in air from room and passes it
over heating coils
• Heated air enters ventilation ducts & dryer
tubes & then blows over film
• Moist warm air vented
89. Processing Rates
• Amount of time it
takes a film to go
through processor
– ranges from 45-
210 seconds
• Film manufacturers
determine
temperatures and
replenishment
rates
Processing Times
Developer 20-25secs
Fixer 20
Wash 20
Dryer 25-30
Travel Time 10
Total Time 90 sec
90. Daylight Automatic Processors
• Enable film to be
processed without need
for darkroom
• Special cassettes
• Increase in department
efficiency, no need for
special darkroom staff
• Disadvantages
– Cost
– Mechanical breakdowns
91. Automatic Film Processing:
Benefits
• Compact size
• Faster
• Density and contrast is constant
• Time and temperature controlled
• Produces dry radiograph
immediately
92. Automatic Film Processing:
Disadvantages
• Artifacts caused by rollers.
• Expensive and requires maintenance.
• Manual processing required as a back up
in case of break down
95. Development
Metallic Silver converted into Black metallic silver
3-5 min at 20OC
Main Constituents
Developing agentmetol-hydroquinone
Accelerator keeps solution alkaline
Restrainer ensures only exposed silver halides converted
Preservative prevents oxidation by air
Processing Systems
Replenishment
Purpose – to ensure that the activity of the developer and the
developing time required remains constant
Guideline – 1. After 1m2 of film has been developed,
about 400 ml of replenisher needs to be added 95
97. Fixer
• Sodium thiosulphate or ammonium thiosulphate
Functions:- 1. Removes all unexposed silver grains
2. Hardens the emulsion gelatin
• Clearing time - The time taken for the radiography to loose its
milky appearance.
• Fixing time - Twice the clearing time
Processing Systems
97
98. Processing Systems
Running water
• Films should be washed in a tank with
constant running water for at least 20 minutes.
• Insufficient washing the film can caused the
yellow fog appears.
98
