Processing Of X-Ray Films Question And Answers

Processing Of X-Ray Films

Question 1. Write short note on “X-ray developer”.
or
Write short note on developer.
or
Write short note on reducing solution.
Answer.

X-ray Developer:

• Developer distinguishes between the exposed and unexposed silver halide crystals.
• The developer initiates a chemical reaction that reduces the exposed silver halide crystals into metallic silver and creates dark or black areas on a dental radiography.
• At the same time, the unexposed silver halide remains virtually unaffected by the developer.
• The reducing agent acts as developer are catalyzed by neutral silver atoms at the latent image sites.

Read And Learn More: Oral Radiology Question And Answers

X-ray  Developing solution

The developing solution contains four components, all dissolved in water.

• Developer (Reducing agent).
• Activator.
• Preservative.
• Restrainer.

X-ray  Other ingredients

• Hardener
• Fungicide
• Buffer
• Solvent.

X-ray  Reducing agents

• The primary function of the reducing agents/developing agents is to amplify the latent image by converting the exposed silver halide crystals into metallic silver grains.
• The electrons from the developing agents are conducted into the silver halide crystal and reduce the constituent silver ions (approximate 1 billion to 10 billions) to solid grains of metallic silver.

X-ray  Commonly Used Reducing Agents

• Hydroquinone (para-dihydroxybenzene).
• Metol or elon (monomethyl para-amine phenol sulphate).
• Metol phenidone (1-pheny 3-pyrazolidone).
  • Hydroquinone is a benzene derivative and is concerned with the production of high contrast in the radiograph. lt is very sensitive to temperature changes. Films are best developed at 70° F for 5 min.
  • Metol or elon is a by-product of aniline dyes and helps to develop the shadow areas of gray on the film and brings out the detail. It does not produce a high contrast. lt is less sensitive to temperature changes.
  • Metol phenidone is an efficient activator for hydroquinone at a very low concentration and works at lower alkalinity. It has longer keeping properties and is less likely to cause dermatitis. It is more commonly used in automatic processor.

X-ray  Activator

• Sodium carbonate or potassium carbonate is used as a activator.
• It provides alkaline medium above pH 11 which is needed for hydroquinone to act. Activator also soften gelatin of the emulsion.
• Activator causes the gelatin to swell so that the developing agents can diffuse rapidly into the emulsion and reach the silver bromide crystals. The component of developer makes it soapy to touch.
• Various other activators used are sodium hydroxide, sodium metaborate and sodium tetraborate
• Excessive alkalinity will lead to rapid reduction even of unexposed silver bromide crystals and produces fog.

X-ray  Preservative

• The developing solution contains an antioxidant or preservative, usually sodium sulphite.
• Sodium sulphite inhibits the tendency of the developing agent to combine with oxygen dissolved in water or air. It therefore acts as a preservative and keeps the solution in usable condition for several weeks.
• Oxidation of the developing agents form colored substances which would stain the film and add to the film fog.

X-ray Restrainer

• Usually potassium or sodium bromide is added to the developing solution as restrainer.
• Restrainers prevent formation of chemical fog which is also known as developmental fog.
• Here the added bromide depresses the reduction of unexposed crystals and acts as antifog agent.
• Restrainer also restricts the action of developing agent to the silver halide crystals which are irradiated.

X-ray  Hardener

Glutaraldehyde is added as a hardener. It is added especially in automatic processing, to prevent the emulsion from softening and sticking to the rollers.

X-ray Fungicide

To prevent bacterial growth.

X-ray Buffer

Added to maintain the pH (+ 7) of developer.

X-ray Solvent

• Water isused as a solvent of the chemicals and as a mediumin which they react with the silver bromide of the film emulsion.
• Normal water supply is usually satisfactory but water with a high calcium content may cause some precipitation.
• Water carries metallic impurities or hydrogen sulphide which may cause trouble, to avoid these inconveniences distilled water should be used.

Question 2. Write short note on fixer.
Answer.

Fixer

• The primary function of fixer is to dissolve and remove the undeveloped silver halide crystals from emulsion and harden the emulsion.
• This creates white or clear areas on the dental radiography.
• The presence of unexposed crystals causes film to opaque.
• If the unexposed crystals are not removed the image on the resultant radiograph is dark and non-diagnostic.
• A second function of the fixer solution is to harden and shrink the film emulsion.
• The fixing solution also contain five components, all dissolve in water.
  • Clearing agent
  • Acidifier
  • Preservative
  • Hardening agent
  • Solvent (water)

Fixer Clearing agent

• It is also known as fixing agent.
• It consists of sodium thiosulphate or ammonium thiosulphate.
• Purposeoftheclearingagentistoremoveorclearunexposed as well as undeveloped silver halide crystals from film emulsion which allow light to pass through film image and permit viewing of radiographic image on the view box.
• Clearing agent clears the film so the black image produced due to the developer should be distinguished.

Fixer Preservative

• Sodium sulphite is used as a preservative.
• It causes prevention of chemical degradation of the fixing agent.
• It also helps in clearing of the film by binding to the oxidized developer which is carried to fixing solution.

Fixer Hardening Agent

• Ammonium sulfate/potassium aluminum is used as a hardening agent.
• It leads to the shrinkage as well as hardening of the gelatin in the film emulsion to prevent the oxidation of gelatin and provide protection to it against the scratches.
• This agent also shortens the drying time by reducing the swelling of emulsion at the time of final wash which causes less mechanical damage to emulsion and limit the water resorption.
• If any contaminated alkali from developer is present, it neutralizes it.

Fixer Acidifier

• Here the acidifier used is acetic acid or sulphuric acid.
• Acidifier neutralizes the alkaline developer.
• Acidifier provides necessary acidic medium for diffusion of thiosulphate in emulsion.
• It also provides the acidic environment which is needed by fixing agent.

Fixer Solvent

Water is used as a solvent.

Question 3. discuss in detail about various techniques of processing of X-ray films.
or
Discuss processing of radiograph in detail.
Answer. Following techniques of processing X-ray films are as follows:

• Manual method
  • Time-temperature method
  • Visual method
  • Rapid processing method
• Automatic method
• Monobath method
• Day light method
• Digitalized processing method
• Self-developing films

X-ray films Manual Method

Time-Temperature Method

Manual method consists of following steps:

• Replenish solutions:
  • First step is to replenish the developer and fixer.
  • Eight ounces per gallon of fresh developer and fixer are made to maintain the proper strength of each solution.
  • Solutions are checked to ensure that the developer and fixer cover the films on the top clips of the film hangers.
• Stir solutions:
  • Both the developer and fixer are stirred by a separate paddle to mix the chemicals and equalize the temperature throughout the tanks.
  • By using separate paddle chances of cross-contamination are reduced.
  • Proper developing time varies with the temperature of the solution; the temperature of the developer should be checked after stirring.
• Mount films on hangers:
  • The exposed film is removed from its light proof packet or cassette, under safety light illumination in the darkroom.
  • Films are held only by their edges. This avoids damage to the film surface.
  • Care should be taken that film is not bent and the emulsion is not touched with wet fingers.
  • Bare film is clipped onto a film hanger, one film to one clip.
• Set Timer:
  • Temperature of the developer is checked.
  • The interval timer is set to the time indicated by the manufacturer for the solution temperature.
  • For intraoral film processing, the following developing times are used.

• Developing of film:
  • The timer is started and the hanger and films are immersed immediately in the developer.
  • The hanger should be agitated mildly for 5 seconds to sweep air bubbles off the film.
  • The films are left in the developer for the pre determined time with out further agitation.
  • The films are removed and the excess developer is drained into the water bath.
• Rinsing of film:
  • As the films are developed the film hanger is removed from the developer solution tank and is placed in the running wash bath for 30 seconds.
  • Films are agitated continuously in the rinse water to remove excess developer and thus slow the development and minimize contamination of the fixer solution.
• Fixing of film:
  • Hanger and film are then immersed in the fixer solution for 4 minutes and agitated for 5 seconds every 30 seconds.
  • This eliminates bubbles and brings fresh fixer into contact with the emulsion.
  • Excess fixation is avoided, this reduces the density of the film.
  • When the films are removed, then excess fixer is drained into the wash bath.
• Wash and dry:
  • After fixation of the films is complete, they are placed in running water for at least 10 minutes to remove remaining processing solutions.
  • After the films have been washed, surface moisture is removed by gently shaking excess water from the films and hanger.
  • Films are dried in circulating, moderately warm air.
  • If the films dry rapidly with small drops of water clinging to their surface, then this uneven drying causes distortion of the gelatin resulting in spots that frequently are visible and detract from the usefulness of the finished radiograph.
  • After drying, the films are ready to mount.

X-ray films Visual Methods

• It is a type of manual processing method.
• This method is done in the darkroom under safety light conditions.
• In this method an exposed X-ray film is immersed in developing solution and is viewed under the safelight for emerging the clear image.
• As image appears, the film is washed and is immersed in fixing solution.

X-ray films Rapid Processing Methods

Manufacturers have created rapid processing solutions which develop a film in 15 seconds at room temperature. These solutions consist of higher concentration of hydroquinone and a more alkaline pH.

X-ray films Automatic Method

It uses the equipment, which automate all of the processing steps. They are of two types, i.e.

• Automatic dunking models which produces a washed film which has to be dried.
• Miniature roller type which produces a dry film.

X-ray films Mechanism

The processor consists of transport mechanism which picks the unwrapped film and passes it via developing, fixing, washing and drying sections. This all is done through rollers which are driven by constant speed motor.

X-ray films Monobath Method

• In this method, developer and fixer are combined in one solution.
• Fixer is alkaline and does not neutralize the developer.
• The monobath is sprayed into a special waterproof film packet and the film is developed by rubbing the film packet.

X-ray films Daylight Method

It is done in a special device which consists of safe light filters and two glove-like compartments by which operator can put his hands and develop the films. Films are opened and processed in a subdued day light.

X-ray films Digitalized Processing Method

The digital images are processed by two systems, i.e.

• CR system or computed radiography system
• DR system or digitalized radiography system.

CR system: In this system, an IP cassette is used.After exposing, the cassette is loaded in a reader unit. The image is read-off and cassette is cleared. Captured image is transferred to workstation where operator views same on monitor. Image can be enhanced, restored, analyzed, compressed or synthesized and output can be taken on printer.

DR system: In place of a cassette, a sensor is used which is directly connected to the workstation through cables or wireless devices. Image is analyzed, interpreted and is stored to other departments.

Self-developing Films

• In this, X-ray film lies in a special sachet which consists of a developer and fixer.
• Following with exposure the developer tab is pulled and developer solution is released which run towards the film and massaged around it.
• After the gap of 30 seconds, fixer tab is pulled and fixer solution is released which run down over the film.
• As fixing is over the chemicals are discarded and film is rinsed thoroughly under running water for 10 min.

Question 4. define latent image. discuss processing of a radiographic film in detail.
Answer. A radiographic film is a recording medium used in dental radiography. When this film is exposed to the information carrying beam of photons exiting an object, the photosensitive silver halide crystals in film emulsion interact with these photons and are chemically changed. These chemically altered crystals said to constitute latent image of film.

Processing is the term which is used to describe the sequence of events which are required to convert the invisible latent image contained in sensitized emulsion to visible permanent radiographic image.

Radiographic Film Types of Processing

• Manual method
  • Time temperature method
  • Visual method
  • Rapid processing method
• Automatic method
• Monobath method
• Day light method
• Digitalized processing method
• Self-developing films

Question 5. What is latent image? describe in detail formation of latent image.
Answer.

Definition of Latent Image

A radiographic film is a recording medium used in dental radiography. When this film is exposed to the information carrying beam of photons exiting an object, the photosensitive silver halide crystals in film emulsion interact with these photons and are chemically changed. These chemically altered crystals said to constitute latent image of film.

Formation of Latent image

• Emulsion of the film is formed of silver bromide and silver iodide crystals which are precipitated in gelatin. They are layered over a thin sheet of transparent plastic base.
• Silver halide crystals get sensitized chemically due to the presence of sulphur compounds which leads to physical irregularities in the crystals produced by iodide ions known as latent image sites.
• The latent image sites leads to the image formation by trapping electrons generated when emulsion is irradiated.
• As silver halide crystals get irradiated by X-ray photons, it results in release of electrons by bromide ions which get converted to bromine atoms by removal of an electron.
• The recoil electron produced has sufficient kinetic energy which causes its movement in crystal and strike the image site leading to negative charge in that region.
• Free positively charged interstitial silver ions are attracted to negative latent image site and neutralize image site resulting an atom of metallic silver deposited at the site.
• As film is exposed to radiation the aggregated silver atoms at latent image sites forms latent image.
• The metal silver presents at each latent image site catalyzes the development of the halide crystal in which it is formed and renders the crystal sensitive to development and image formation.
• Larger is the aggregate of silver atoms, more sensitive is the crystal to the effects of the developer.
• Primary action of processing solution is to convert the crystals with latent images to black metallic silver grains that can be visualized and to remove the unexposed silver bromide crystals.

Question 6. Write short note on composition and function of fixer solution.
or
Write short note on composition of developer and fixer.
or
Describe compositions and functions of processing solutions.
or
Write short note on composition of developer solution.
Answer.

 

Question 7. Write short note on darkroom.
Answer. Primary function of a darkroom is to provide a completely darkened environment where X-ray film can be handled and processed to produce diagnostic image in an efficient, precise, and standardized procedure.

Equipment of darkroom

Darkroom consists of the following infrastructure:

• Safelights
• Visible light source (tubelights)
• Working area to load extraoral cassettes
• Processing tanks
• Thermometer and stop clock
• Dryer
• Storage facility for unexposed films
• Exhaust and appropriate ventilation.

Requirements of a darkroom

A well-planned darkroom is necessary for the easy processing.

An ideal darkroom should have:

• Convenient location
• Adequate size with ample working space
• Correct lighting equipment
• Adequate storage
• Temperature and humidity is controlled.

Other miscellaneous requirements of darkroom consist of waste basket for disposal of all film wrappings and there should be a X-ray view box.

Convenient Location

Location of the darkroom should be convenient.

Ideally the darkroom should be located near to the area where X-ray units are installed.

Adequate size with ample Working space

• Darkroom should be wide enough to accommodate film processing equipment and also have ample working space.
• As smaller developer and fixer tanks can be utilized, may be of small sizes. The average size required is 6 ft × 8 ft.
• Ceiling of the darkroom should not be less than 2.7 m high.
• Floor of darkroom should be non-slippery and is resistant to staining.
• Ceiling and walls should be very well painted. For protection from the ionizing radiations, walls should have 2.0 mm equivalency of lead.A25-mm thick barium plaster can also be used. The area where films are stored should be covered well.

Correct Lighting Equipment

• Darkroom should be strictly light tight, i.e. light proof.
• Door of the darkroom should be light tight along with proper lock to avoid accidental opening.
• There are two types of lighting essential in a darkroom, i.e. room lighting and safe lighting.

Room lighting

• In can descent room lighting is strictly needed for procedures which are not associated with the processing of films.
• An overhead white light is needed which provides adequate illumination for the size of the room. It is very necessary to perform tasks such as cleaning, stocking materials, and mixing chemicals in this light.

Safe lighting

• Safe lighting is a special type of lighting used to provide illumination in the darkroom.
• Safelight typically consists of a lamp which is equipped with a low wattage, i.e. 15 watt bulb and a safelight filter. This filter removes the short wavelengths in the blue-green portion of the visible light spectrum which are responsible for exposing and damaging X-ray film.
• A universal safelight filter should be recommended for use in a darkroom in which both extraoral screen films and intraoral films are processed. GBX-2 safelight filter by Kodak is the most recommended one.

Adequate storage

• Storage space in the darkroom must include ample space for the chemical processing of solutions, film cassette and other various miscellaneous radiographic supplies.
• It is recommended that storage of unopened boxes of film should be in the darkroom.
• Boxes of opened extraoral film should be stored in the darkroom.Alight tight storage drawer is very necessary to protect the opened boxes of an unexposed extraoral film.

Temperature and humidity control

• Temperature as well as humidity level of the darkroom should be strictly controlled to prevent film damage. Room temperature of 70°F should be recommended; if the room temperature exceeds 90°F the film fog results.
• Relative humidity level between 50% and 70% should be maintained.Ifhumiditylevelsaretoohigh,thefilmemulsion does not dry. When humidity levels are very low, static electricity becomes aproblem andthis leads tofilm artifacts.
• Darkroom plumbing consists of both hot and cold running water with their mixing valves to adjust the temperature of water in the processing tanks. A utility sink along with the running water is useful in the darkroom.

Question 8. Write short note on penny test.
Answer. Penny test is also known as coin test.

• Penny test is the test for checking unsafe illumination
• Penny test is done to evaluate fogging caused by inappropriate safe lightening conditions.

Penny Test Procedure

• Shut all the lights and put on the safe light.
• Film packet should be opened and base film is placed in the area where films are usually unwrapped.
• Place the film on flat surface at least 4 feet distance from safe light
• A coin should be placed on the film and left in same position for approximately 5 minutes. Now remove the coin and process the film.
• Test film should be developed as usual.

Penny Test Inference

• If image of the coin can be seen on resultant film, room is not light safe for the film which is tested.
• If no visible image is seen on the resultant film, then safe lightening is proper and should be proceed with film processing.

Question 9. Write in detail about interaction of X-rays with matter. add a note on chemical changes occurring in the film after exposure and formation of latent image.
Answer. For details about interaction of X-rays with matter refer to Ans 2 of chapter PROPERTIES OF X-RAYS.

Note on chemical changes occurring in the film after exposure and formation of the latent image

• Film emulsion is formed of silver bromide crystals and silver iodide crystals that have been precipitated in gelatin and layered on a thin sheet of transparent base.
• Silver halide crystals are imperfect in many aspects and they consist of few of the free interstitial silver ions in the spaces between the crystalline lattice.
• There is presence of physical distortion in the regular rectangular array of silver and bromide ion crystals due to the presence of iodine atom occupying some of the bromide sites.
• Silver halide crystals are chemically sensitized by presence of sulfur compounds which cause physical irregularities in the crystal produced by iodide ions, and these are known as latent image sites.
• Function of the latent image sites is to begin process of image formation by trapping electrons generated when the emulsion gets irradiated.
• When silver halide crystals are irradiated by X-ray photons it will result in the release of electrons by bromide ions which get converted to bromine atoms, by the removal of an electron (recoil electron). This recoil electron produced has sufficient kinetic energy by which it moves in the crystal and strikes the image site, imparting a negative charge to that region.
• Free, positively charged interstitial silver ions get attracted to negative latent image site and neutralize the image site with the result that an atom of metallic silver is deposited at the site.
• After the exposure of film to radiation, aggregate of silver atoms at latent image sites, comprises the latent image. This is the metallic silver at each latent image site that catalyses development of halide crystal in which it formed and renders the crystal sensitive to development and image formation.
• So, primary action of the processing solutions is to convert crystals with latent images into black metallic silver grains that can be visualized and to remove the unexposed silver bromide crystals.