Transcript Film processing 2 - Sri Lanka School of Radiography 1957-2014

Film processing 2
Processing cycle
Dev.
Rinse
Fix
Wash
Dryer
Developing
Dev
Rinsing (stop bath)
Rinse
Rinsing in manual
processing
Immediately after development the
film is dipped in the water in order
to:
i.
Stop development
ii.
To wash the developer from the
surface of the film – (reduces
developer carry over to fixer)
Rinsing in Automatic
processing?
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No rinsing stage
The developer is removed from the
film surface by passing it through the
special type of rollers called “squeegee
rollers”
Alkaline Developer is neutralized by
the acid in the fixer
Fixing
Fixer
Functions of fixing
To stop any further development
 Clears the image (making the
background transparent to light)
 Makes the image permanent (fixed)
(no more sensitive to light)
by Removing the undeveloped silver
bromide crystals from the emulsion
 Hardens the emulsion

Fixer constituents
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Solvent
Fixing agent
Acid
Hardener
Buffer
Preservative
Anti-sludging agent
Functions of fixer
constituents
Constituent
Function
Solvent
(water)
Carrying medium for the active
ingredients
Controls the acidity by diluting
Fixing agent
(Sodium
Thiosulphate
/Ammonium
Thiosulphate
Combines with insoluble AgBr to
form soluble compounds
(Ammonium ArgentoThiosulphate & NH4Br
Acid
(Acetic acid – pH 4.0 –
4.5)
To stop development
To provide suitable
working environment for
hardening agents
Hardener
(Aluminium chloride &
aluminium sulphate)
Hardens the emulsion to
limit water absorption,
to reduce drying time,
to minimize physical
damage
Buffer
(Sodium
acetate &
acetic acid)
Controls the pH in a precise range
in order to:
i. Prevent sulphurization
ii. Neutralize the developer
iii. Optimum hardening
Preservative
(Sodium
sulphite)
Retards the decomposition of
thiosulphate and delays the onset
of sulphurization
Anti-sludging
agent (Boric
acid)
Reduces the formation of sludge
of insoluble aluminium
compounds by the aluminium
salts used as the hardner
Factors affecting Fixation
The quality and quantity of fixation
depends on the:
 Constitution and activity of fixing
solution
 Fixer temperature
 Fixing time
Constitution & activity of
fixing solution
At a given temperature the activity of fixer
solution depends on:
 Fixing agent
 Concentration of fixing agent
 Amount of hardener present
 The amount of soluble silver compounds
and soluble halides present
 pH
Fixer temperature
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The activity of fixing agents increases
with temperature.
But high temperatures cause emulsion
swelling and becomes susceptible to
damage.
However precise control of
temperature is not necessary
Fixing time
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The fixing time should be long enough
to complete the fixing process.
The required time for complete
fixation depends on the
i. activity
i. type of film emulsion
iii. Agitation of fixer solution
Replenishment of Fixer
Replenishment of fixer is necessary to
i.
Maintain the activity
ii.
Maintain the volume
The rate of replenishment depends on
i.
Area/number of films processed
ii.
Type of emulsion/film
iii. Type of image
Replenishment of
chemicals
Manual processing
Suitable quantity is
added manually at
regular intervals
Automatic processing
Added automatically
by the replenishment
pumps at a given
rate for each film
processed
Washing
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Removes the fixing solution contaminated
with silver complexes and ammonium
halides from the film surface and from
film emulsion
Running water is used to maintain a
concentration gradient and to improve the
diffusion rate of chemicals from the
emulsion to water
Factors affecting washing
efficiency
Type of film emulsion
 Condition of fixing solution
 Condition of water
 Agitation of water
 Temperature of water
 Washing time
Thiosulphate level of < 3 microgram/square
cm is recomended
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Drying
Removes all of the surface water and most of
the water retained in the emulsion
Manual processing:- Keep the film in a drying
cabinet in which hot air is circulated. Takes
about 10-15 minutes
Automatic Processing:- Surface water is removed
by squeegee rollers ; evaporation removes the
emulsion water.
25 sec in a 90 sec cycle
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Factors affecting drying
time & efficiency
The wetness of the emulsion; governed
by:
i. hardness of the emulsion
ii. emulsion thickness
 The drying conditions; governed by:
i. Air humidity
ii. Air Temperature
iii. Air circulation – rate of change
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Summary
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If a film is not processed properly the
whole effort made in the x-ray room or
in the ward to obtain a good
radiograph will be lost
It is essential to pay similar attention
to film processing as you pay at the xray room or in the ward when taking
the x-ray