05 Flm Processing

X-RAY FILM, FILM PROCESSING & SHOOTING TECHNIQUES  X-ray

film  Film processing  H& D curves  Reduction of scatter  Single wall & double Techniques  Multi film techniques etc

wall

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FILM PROCESSING

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FILM PROCESSING STEPS 

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Immersion in a developer solution & agitation  Exposed Ag grains reduced to black metallic Silver Water rinse / Acid stop bath  To stop developing action on the film. Immersion in fixing bath & agitation  Unexposed Ag grains washed-off & Image fixed;Film hardened Water wash  To remove fixer & products of fixing from film emulsion. Immersion in a wetting solution  To help even drying & prevent spotting on films Drying 3

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Development A chemical reduction in which silver halides reduced to metallic silver Reaction limited to those grains that have received more than a certain minimum exposure to radiation Role of latent image in development    

Acts as an electron-conducting bridge A molecule of a developing agent gives an electron to an exposed silver bromide grain, not to an unexposed grain This electron combine with a silver (Ag+) ion of the crystal producing an atom of silver This process repeated many times  until all the billions of silver ions in a photographic grain turned into metallic silver. 4

 Development

process  electrons supplied by developer solution  combine with silver ions of crystal lattice.  Latent image process  electron is freed by the action of radiation  Both processes involve 

union of a silver ion and an electron to produce an atom of metallic silver. 5

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Developer constituents 

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Developing Agent  Metol-hydroquinone or Phenidone-hydroquinone Reduces exposed silver halide grains to metallic silver Activity of developing agents depends on ,alkalinity of solution

Accelerator (Alkali)  

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Speeds-up development Provides buffering action to counteract liberation of hydrogen ions, a tendency toward acidity Alkali chemicals:  Sodium carbonate, Potassium carbonate, Sodium hydroxide, Potassium hydroxide, borax

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A Preservative To protect developing agent from oxidation by air , Sodium sulfite.  Maintains development rate (alkaline reaction)  prevents formation of staining of photographic layer. A Restrainer Anti-foggant, Potassium bromide   

decreases possible concentration of silver ions in solution, protect unexposed grains from the action of the developer Both tend to reduce formation of fog.

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MANUAL PROCESSING STEPS  

Exposed film mounted on a hanger & held securely Film immersed for pre-determined intervals in 

Developer solution

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Powder form economical to buy, dissolved in water liquid form offers greater convenience in preparation level of the developer solution must be kept constant By adding replenisher activity of developer kept constant At frequent intervals films must be agitated

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CONTROL OF TEMPERATURE AND TIME • Temperature checked immediately before films immersed in developer • mechanical refrigeration to maintain developer Temperature • Development Temperature & Time • 5 to 6 Minutes at 20°C ; No Guesswork. • A temperature below 16°C 

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High temperatures above 24°C 

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retards developing the action & result in underdevelopment, Produces fog

softens emulsion to separate from the base ice placed directly in processing solutions 

will dilute developer solution & cause contamination..

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FILM AGITATION 

Hangers tapped two or three times on the upper edge of the tank 

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Acceptable agitation  

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to dislodge any bubbles clinging to emulsion.

films are shaken vertically and horizontally moved from side to side for a few seconds every minute

Methods of renewal of developer at the surface of film   

obtained by lifting the film clear of the developer allowing it to drain from one corner for 2 or 3 seconds reinserting it into the developer & then repeating the procedure

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FILM AGITATION 

Developer artefacts  reaction products of development flow downward over film surface  retard development in areas beneath  Result-in variations in film density (uneven development) 

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show up as streaks

Too many hangers in developer 

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causes streaks & mottled appearance in radiographs in areas that receive a uniform exposure

“sight development“  

leads to a high level of fog caused by excessive exposure development.

to

safelights

during

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STREAKS

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ACTIVITY OF DEVELOPER SOLUTIONS 

Developing power decreases because of  

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developing agent consumed as it changes exposed silver bromide to metallic silver restraining effect of accumulated reaction products of the development

Decrease in activity   

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depends on the number of films processed Density to which they are processed. aerial oxidation

Replenishment means  

addition of a stronger-than-original solution maintaining liquid level in the developing tank Restoring developer to its approximate original strength. 13

REPLENSHMENT 

Quantity of replenisher required depends on 

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replenisher added at frequent intervals 

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as density increases after replenishing are kept at a minimum

Quantity of replenisher added each time 

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average density of radiographs processed

not to exceed 2 %-3% of the volume of the developer

solution discarded when the replenisher used equals  

two to three times the original quantity of the developer After three months 

because of aerial oxidation . buildup of gelatin, sludge, and solid impurities.

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ARRESTING DEVELOPMENT  

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Stop Bath   

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films removed from developer allowed to drain 1or 2 seconds (not back into the developer tank) Immersed & stirred in stop bath (18-21°C) 30-60 seconds or rinsed in clean running water 2 min 28 % acetic acid 125 mL/litre of water glacial acetic acid35 mL/ litre of water Add glacial acetic acid to the water slowly, stirring constantly

If development is not arrested using stop bath   

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Upset Chemical balance of fixer solution destroy hardening action Artifacts (stop-bath stage)

Streakiness stains in radiographs 15

 FIXING

to remove all of the undeveloped silver salt of the emulsion  leaving the developed silver as a permanent image.  hardening the gelatin  film will withstand subsequent drying with warm air Clearing Time  Interval between placing the film in the fixer solution and disappearance of diffuse yellow milkiness  Films agitated in fixer, every 2 minutes  total fixing time should be 2 times clearing time, not to exceed 15 minutes 

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usefulness of a fixer solution ended, when clearing requires long interval  when it has lost its acidity  An exhausted fixer solution causes abnormal swelling of the emulsion and drying unduly prolonged Artifacts (Fixing stage)  At high temperatures reticulation or sloughing away of emulsion takes place  neutralization of the acid in the fixer solution frequently causes colored stains to appear on the processed radiographs. 

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Washing    

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X-ray films should be washed for 30 minutes in running water at 16 to 27°C circulated so that entire emulsion area, receives frequent changes, rate of water flow of four renewals per hour Bar of the hanger and the top clips should always be covered completely by the running water Films placed in the wash tank near the outlet end & moved toward the inlet

Artifact (washing stage) 

insufficient washing  leads to later discoloration or fading of the image

cascade washing unit.

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 DRYING  

suitable driers used with built-in fans, filters and heaters or desiccants Radiographs dry best in warm, dry air that is changing constantly.

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Prevention of water spots

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When films removed from wash tanks drops of water cling to the surfaces of emulsions  Areas under the drops dry more slowly than the surrounding areas If films dried rapidly,.  uneven drying causes distortion of gelatin, changing the density of the silver image, 

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results in spots

Prevention methods  washed films immersed for 1 or 2 minutes in a wetting agent  wetting agent solution causes surplus water to drain off the film more evenly  reduces number of clinging drops & drying time .

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Chemistry of Automated Processing Automated processing a system depending on interrelation of mechanics, chemicals, and film. mixing instructions with chemicals followed exactly. processing chemicals prevent the emulsion from swelling or becoming either slippery, soft, or sticky. if a film becomes slippery, it could slow down in the transport system,  

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films following it could catch up and overlap or get stuck or even wrap around a roller.

If the emulsion becomes too soft it is damaged by rollers. 20

Automatic Film-Processing 

The roller transport system 

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rollers driven by a constant speed motor. rollers arranged in a number of assemblies    

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backbone of an automated processor

entrance roller, racks turnarounds (which reverse direction of film travel within a tank) crossovers, (which transfer films from one tank to another), and a squeegee assembly (which removes surface water) after washing cycle

time interval from insertion of an unprocessed film to the delivery of a dry radiograph 

8 to 12 minutes. 21

Filing Radiographs  placed in a heavy manila envelope of the proper size  essential identification data written on the envelope filed.  Envelopes having an edge seam, rather than a center seam, and joined with a non hygroscopic adhesive Ideally, radiographs should  be stored at a relative humidity of 30 to 50 percent. 

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