Film Processing PDF

Film Processing Film processing is chemical procedures that convert the latent (invisible) image into the visible radiographic image. Latent image: hidden (invisible) image formed from interaction of x-ray photons with the halide crystals in film emulsion and it ca...

Film Processing Film processing is chemical procedures that convert the latent (invisible) image into the visible radiographic image. Latent image: hidden (invisible) image formed from interaction of x-ray photons with the halide crystals in film emulsion and it cannot be seen unless the film is processed is the pattern of stored energy that creates an invisible image on the exposed film Film x-ray latent (invisible) image processing visible image Film emulsion contains: Ag Bromide: more than AgI Silver halide Ag Iodide (traces): larger than Ag Bromide Interstitial Ag ions (free Ag+ ions) Sulfur compounds Sensitivity sites radiosensitive and are created by the physical irregularities made by the addition of iodide which are larger in size than the bromide. x-ray exposure Sensitivity sites latent image site 1 Latent image site: it is formed of: - Unexposed crystals: enamel, amalgam does not pass x-rays - Partially exposed crystals: e.g. x-rays passed through bone - Totally exposed crystals: e.g. x-rays passed through air, soft tissue, pulp space, PDL space Exposed crystals: - When the silver halide (silver bromide and silver iodide) crystals are irradiated, x-ray photons interact primarily with the bromide ions. These interactions result in the removal of an electron from the bromide ions. (ionization) - The free electrons move through the crystal until they reach a sensitivity site - The negatively charged sensitivity site then attracts positively charged free interstitial silver ions. - When a silver ion reaches the negatively charged sensitivity site, it is reduced and forms a neutral atom of metallic silver called silver specks - The sites containing these neutral silver atoms are now called latent image sites 2 Steps of processing Developing Rinsing Fixing Washing Drying 1- Developing: The developer solution is the first solution into which the films are placed Functions of developing: The developer chemically REDUCES the ionized silver bromide crystals by donating electrons, removing the halides and precipitating metallic silver in the emulsion layer. This precipitation corresponds to the black (radiolucent areas in the radiograph) The silver specks at the latent image sites act as a catalyst during developing Ingredient Chemical Function Developing Hydroquinone - Converts exposed AgBr crystals to agent black metallic silver. Slowly generates the black tones in the image. - It is temperature sensitive (inactive below 60 F° and very active above 80F°) Elon (metol) - Converts exposed AgBr crystals to black metallic silver. Quickly generates the grey tones in the image. - It is temperature insensitive. Activator Sodium - Provides alkaline pH necessary for bicarbonate developing agents. - Softens gelatin to swell so that the developing agents can diffuse more rapidly into the emulsion and reach the AgBr crystals. Preservative Sodium sulfite - Antioxidant: protects the developer from oxidation by atmospheric oxygen thus extends its useful life. Combines with the brown oxidized developer to produce a colorless soluble compound Restrainer Potassium - Restrains development of unexposed bromide silver halide crystals (controls activity of the developer). Acts as anti-fog agents & increases contrast 3 2- Rinsing The films are rinsed in water for 10-20 seconds before they are placed in the fixer Functions of Rinsing: It stop the developer diffused into gelatin so reduces the speed of development It removes the alkaline activator preventing neutralization of the acid fixer The rinsing process is typical for manual processing but is not used with automatic processing 3- Fixation: the film is then placed in a fixer solution For permanent fixation, the film is kept in the fixing solution for a minimum of 10 minutes. Improperly fixed films turn brown over time. Functions of Fixation: To stop further development via making acidic media Dissolve and remove undeveloped/unexposed crystals It fixes the image “no longer sensitive to light” Harden and shrink the film emulsion Ingredient Chemical Function Fixing agent Sodium thiosulphate Remove all unexposed and Ammonium thiosulphate undeveloped crystals from the emulsion Acidifier Acetic acid Neutralizes the alkaline developer and stops further development. Preservative Sodium sulfite Prevents deterioration of the fixing agent. Hardening Potassium Alum Shrinks and hardens the gelatin agent Emulsion changes during film processing: A) Before exposure, many silver bromide crystals are present in the emulsion B) After exposure, the exposed crystals containing neutral silver atoms at latent image sites constitute the latent image (shaded areas in the crystals) 4 C) The developer converts the exposed crystals containing neutral silver atoms at the latent image sites into solid grains of metallic silver. D) The fixer dissolves the unexposed, undeveloped silver bromide crystals leaving only the solid silver grains. 4- Washing: Proper washing takes 20-30 minutes under running water Functions of washing: Removes all thiosulfate complexes as retained ones tends to react with silver to form silver sulfide resulting in brown color of the film. 5 5- Drying: The drying medium could be dry air of low humidity or Heated air Function of drying: To remove all the surface water and most of that retained in the emulsion in order to be ready for interpretation without deterioration Drying by: - Electric fans - Film hangers - Heat dryer Finally: - The visible image will contain black, white and gray areas. - The gray areas seen on the final radiograph are the result of having black areas and white (clear) areas in close proximity. - These colors are corresponding to the degree of x-ray beam attenuation by the object being radiographed The dark room (Processing room) It is a room in the dental office where x-ray film can be handled and processed to produce diagnostic radiographs Dark room requirements: Location (site): Convenient & centrally located Near the X-ray units but well protected from radiation Size: The size is governed by: - The number of processed radiographs - The number of working personnel - The type of processing equipment used (manual versus automatic processing) - The space required for radiograph duplication and film storage Lightening The darkroom should be light-tight: - Revolving doors - Door less maze - Light tight door 6 2 types of lightening are required: Safe light – Room light. Safe light: does not rapidly affect opened films but permits one to see well enough to work in the area low intensity long wavelength (red, orange or yellow) 15-watt At least 4 feet above the surface where opened films are handled 4 feet = 48 inches = 121.9 cm Film handling under a safelight should be limited to about 5 minutes Number: 1-2 according to the size of the darkroom How safe is the safe light? film coin test A test for safelight safety. A coin is placed on the center of an unwrapped, unexposed film on the bench top under safelight conditions. After 3 minutes of exposure to the safelight, the film is processed. If the film shows a white outline of the coin in the center of the film, the light is not safe 7 Room light: Incandescent (not fluorescent) room lighting is required for cleaning, stocking materials, and mixing chemicals The fluorescent light is contraindicated because of its afterglow which may affect the opened films at the time just after the light is turned off. Other light sources: should be present as view box for film reading, an outside warning light to warn against entrance of the darkroom during processing. Processing tank: - It is a container divided into compartments to hold the developer and the fixer solutions and water bath. It consists of a master tank and two insert tanks. - The master tank is about 8 x 10 inches that can serve as a water jacket for the 2 removable inserts that fit inside. The insert tanks usually hold 3.8 L (1 gallon) of developer or fixer and are placed within the outer, larger master tank. - The outer tank holds the running water for maintaining the temperature of the developer and fixer in the insert tanks and for washing films. The tank must have hot and cold running water and a means of maintaining optimum processing temperature of 68˚F. It should also contain an overflow pipe to get rid of the excess water. - The developer customarily is placed in the insert tank on the left side of the master tank and the fixer in the insert tank on the right. - All 3 tanks should be made of stainless steel, porcelain or glazed earthware (all of which do not react with the processing solutions and are easy to clean). - The master tank should have a cover to reduce oxidation of the processing solutions, protect the developing film from accidental exposure to light, and minimize evaporation of the processing solutions. - Under normal working conditions, the developer and fixing solutions should be changed every 2 to 3 weeks, as the processing solutions are weakened by time. A normal workload is 30 films per 8  day. In busy offices, solutions may have to be replaced more frequently than every 2 weeks. Thermometer: Necessary in manual processing (time temperature method), and used to determine the temperature of the developer solution. Thermometer is hanged in the developer tank Film hangers: A film hanger is a device equipped with clips used to hold the film during processing. It is made of stainless steel. Film hangers are necessary for manual processing. 2 types are present: intraoral and extraoral. Intraoral film hangers are of various sizes & contain clips for 1-14 films They should be numbered to avoid mix-ups. Films should be mounted on the hanger clips with the short dimension to avoid overlapping of films. 9 not in the water bath. Techniques of processing: Techniques of processing Manual Speed processing processing Fixed Visual inspecttion time-temperature method method Manual processing: needs dark room 1. Fixed time-temperature method: 1. Replenish solutions 2. Stir solutions 3. Check the developer temperature 4. Mount films on hangers 5. Set timer 6. Develop 7. Rinse 8. Fix 9. Wash and dry 2. Visual inspection method: Immerse the film hanger in the developer, remove it at frequent intervals and hold it up to the safelight, until fillings or root shapes are visible At that point the films are rinsed and placed in the fixer What If I Have No Dark Room In My Clinic, Shall I Do Radiographs Or Not? day light loader 10  Speed processing: No darkroom is needed 1- Automatic processor The processing steps are the same as for manual processing except that the rinsing step between the processing solutions is eliminated…why? Some differences between manual and automatic processing 1. No stop bath between developer and fixer (rinsing) as rollers remove the chemicals. 2. Higher temperatures for automatic processors. Therefore different chemicals required. 3. Hardener placed in developer in automatic processors 4. Additional hardener is added to the fixer solution. 5. Because of the daylight-loader a darkroom is not required. 6. Because of the heater in the automatic processor, the process is a "DRY TO DRY" process Using the automatic processor, the processing time is reduced by: Elimination of the rinsing step between developing and fixation. Higher temperature of the processing solutions. Higher concentration of the processing solutions. Advantages: - Rapidity - Ease of use - Standardized processing conditions - Elimination of the need to the dark room - Chemicals can be replineshed automatically 11 Limitations (disadvantages): - Expensive - Strict maintenance and regular cleaning are essential - Most equipments process a certain minimum amount of films per day - High temperature produces chemical fog in the final radiographs - Conventional darkroom may still be needed as a backup system 2- Self-developing films Advantages: - No dark room or processing facilities are needed - Time saving Limitations: - Poor overall image quality due to absence of the rinsing step leading to chemical fogging - The image deteriorates rapidly with time - No lead foil inside the film packet - Difficult to use in positioning holder - Relatively expensive 3- Injectable intra-oral films - The processing solutions are injected into the closed packet which is supplied with an injectable site - NO lead foil or black papers - Fogged image 4- Polaroid films 5- Digital processing (filmless technique) 12  MCQs 1- The following are requirements of the dark room except: a- Near to main operating room b- Large enough to allow free mobility of working personnel c- Far from area to film exposure d- Protected from light leakage 2- The component of the developer which is responsible for formation of gray shades of the image is: a- Preservative b- Activator c- Elon d- Restrainer e- Hydroquinone 3- The fixer solution is: a- Acidic b- Alkaline c- Neutral d- None of the above 4- The developer is responsible for: a- White shades of the image b- Gray shades of the image c- Black shades of the image d- Gray and black shades of the image 5- The wattage of the safe light bulb used in the dark room ranges between: a- 10-15 watt b- 5-15 watt c- 15-20 watt d- 20-25 watt 6- Air tightness is an important requirement of the dark room a- True b- False 13 7- Safelight integrity can be checked with: a- A check film b- The “coin” test c- A densitometer d- A colorimeter 8- The ordinary light in the dark room should not be of fluorescent type: a- True b- False 9- The black areas on dental radiograph are created by deposits of black metallic silver a- True b- False 10- Potassium alum is put in the developer to harden the gelatin layer of the film during processing a- True b- False 11- Speeding of the manual processing can be done by: a- Decreasing the washing time b- Using high speed films c- Using less concentrated solutions d- Increasing temperature and concentration of solutions 12- The fixer is the processing solution in which all the unexposed crystals are removed. a- True b- False 13- The disadvantage of the automatic processor is: a- Non-standardization of the automatic process b- Continuous replenishing of the processing solutions c- Low concentration of the processing solutions d- A dark room is needed in case of mechanical problems 14 14- All of the following is considered a speed processing except: a- Automatic processing b- Fixed time-temperature technique c- Injectable intra-oral films d- Self-developing films Look at the following diagram and answer questions A & B 1.___________2________3________ A- The diagram represents ………… B- What does happen during step 2 shown in the diagram? ………. Answers 1- C 2- C 3- A 4- D 5- A 6- B 7- B 8- B 9- A 10- B 11- D 12- A 13- D 14- B 15