An Assignment on
Dark Room Procedure For
Quality Radiography
Submitted to Dr. Manoj Kumar Shah Lecturer Department of surgery and pharmacology IAAS, Rampur campus, Chitwan
Submitted by Suraj Subedi B.V.Sc & A.H 7th semester Roll no 29 IAAS, Rampur campus, chitwan
September, 2010
Introduction The most common errors made in radiography of animals are related to the processing of exposed radiographic film. The area used as a darkroom must be clean, lightproof, and uncluttered. If film should accidentally come into contact with spilled processing chemicals, specific artifacts will appear on the radiograph. Pressure, creasing, buckling or static electricity can also cause artifacts, dictating the need for great care in the handling of film. Because of the variety of errors possible in the darkroom and the frequency of these errors, it is not difficult difficult to explain the trend toward purchase of automatic processors. These units are costly and the cost of maintenance and replenishing of solutions is high. Still, in the practice using radiography frequently, the automatic process may save time and money by decreasing the number of repeat examinations required because of technical problems. It is difficult to en courage courage a technician to perform perform a radiographic examination carefully if the quality of the study is to be lowered by damaging the film in the darkroom. There are basic considerations considerations in construction construction and layout of a darkroom that can assist in l owering the chances of film damage. Nothing is more discouraging than to work long minutes to achieve proper positioning of the patient and then have the study ruined by careless acts in the darkroom.
Gen General Dark room procedures a. Layout b. Light traps and entrance c. Wet and dry benches d. Film pass hatches e. Processing units f. Safe-lights and ancillary equipment g. Storage, handling and loading h. Film processing (automatic and manual) i. Temperature control Darkroom Conf iguratio iguration
Work flow is more important than is room size and shape. The physical layout of the darkroom should consider the following items. If manual processing is performed with wet tanks, there must be dry and wet sections of the room. This enables you to handle film, unload and reload cassettes, and store film in the dry section while the wet section is used only for processing of the film. If used, the pass box should be next to the loading bench. Film hangers can be stored either under or over the loading bench. The bench must be far enough from the wet tanks to prevent solutions from splashing on the film. Film storage bins are a convenient method of storing the open film boxes currently in use. If the number of radiographic examinations performed is low, it may be easier to replace the lid on the film box to keep the remaining film protected from the light. A box opened and reclosed in this manner can be stored on a shelf without risk of light exposure of the remaining film. Location of of the wet film examining area is important. important. This i s a wet, messy, area at the best. The film viewer should be near the fixer tank since most films to be evaluated are taken from the fixer tank, viewed, and then are replaced in the fixer tank for completion completion of the fixation process. Place a tray of some sort under the view box so that some of the splashing of fixer can be controlled. An absorbent towel hanging near this area is of use in assisting in controlling dripping of solutions.
Sinc Sinc ilm ilm i s s in the darkroom darkroom and is is handled without a protec protective over c over in this thi s room room problems problems of film film fogging or undes undesirable bac background expos exposure covering the film fil m often center around the darkroom darkroom Fogging can be due to: y y y
improper us use of the darkroom darkroo m safelight accidental ccidental illum illu mination of the film fil m by vis visible light radiation expos exposure.
Schematic drawing drawing of a darkroom u ing wet-tan wet-tank processing. processing.
Flow of of f ilms ilms f rom rom lef lef t to rig right. ht. The cassette ssette is is opened on the counter top. (a) Where the film film is plac placed on a hanger. The film fil m is plac placed in a series eries of tanks tanks (b) containing developer, rins rinse, fixer and was wash. Note the separation of dry and wet portions portion s of the darkroom darkroom. Safelights Safelights are mounted on the wall (c) A viewbox (d)With drip sink is is available for wet film film viewing .
FEATURES IN A DARKROOM USING WET TANK PROCESSING 1. acc acce ess door
11. 11. exterior warning
2. lightloc lightlo ck entranc entrance
12. 12. view box
3. cassette ssette storage*
13.floating therm thermo-cabinet -cabinets s meter
4. cassette ssette pass pass box*
14. water tem temperature regulator
5. loading benc bench
15. film fil m hangers hangers
6. film film storage
16. hanger storage rac rack
film bin 7. film
rack or film film dryer 17. 17. drying rac
8. was waste bas basket
18. towel light indic indi cating us use*
9. proc processing ssing tanks tanks
19. cloc lock
10. 10. safe lights lights Safelight illum illu mination is i s of critic ritical i mportanc portance in the operation of a darkroom darkroo m. The func fun ction of the safelight is i s to provide suffic uffi cient illum illumination to enable you to work quic qui ckly and effic effi ciently but must be of s of such a type that does does not add fog to the radiographic radiographi c film film. X-ray film fil m is sens ensitive to
light in several regions of the spectrum; therefore, safelights must be covered with the correct filters
___________________________________________________ *may be desirable in certain circumstances
Safelights must: must: 1) be used with the correct filter, 2) be of the correct wattage (standard frosted, 6 1/2 watt to 10 watt, and 3) be the correct distance from film on the counter top. Even following these rules, film can still be fogged if left exposed to the light for a long enough period of time. It is possible that the safelight is satisfactory but outside light is entering the darkroom around a door or through cracks and causing fogging of the film The The f ilm ilm sh should be sensitive to a ligh lig ht energy emitted by th the screen but sh should not be sensitive to th t he ligh ligh t energy emitted by th the saf eligh elight in the darkroom.
The following technique is recommended to evaluate the level of illumination in the room and its effect on the film. place a film on the counter top in a location where you normally unload the cassette and cover it with a heavy cardboard, the film box, or other light opaque material. Position the cardboard so that 1/4 1/ 4 of the film is exposed to the normal illumination illumination of the r oom under that 1/2 of the film is now exposed for an additional 1 minute. shift the cardboard once more so that 3 /4 /4 of the film is now exposed for an additional minute. Finally, remove the cardboard and permit the entire film to be exposed to darkroom light for an additional minute. Process the film in the routine manner and examine it. If the darkroom illumination is safe, none of the film will have any fogging which appears as a darker portion on the film. If there is evidence of fogging, examination of the film will tell you the extent of the exposure and how long you can safely leave a film exposed to the darkroom light before fogging occurs. This same Test can be performed with the safelight off to evaluate leakage of light into the darkroom. X-ray film is highly sensitive to radiation and therefore must be protected from any accidental exposure. If fogging of film occurs, the possibility of the fogging occurring within the darkroom must be considered especially if the room is adjacent to the examination room. A simple test for the possibility of stray radiation reaching the film film bin or box is to tape a dental x -ray film packet with a coin placed to the outside of the film packet on the inside and outside of the door of the film bin. After several weeks, develop the film. If an image of the coin is seen on the film it will be due to radiation reaching the film but being absorbed by the more dense metal coin. DAR DAR ROO
LIGHT GHT FILTER
Ligh Light Sensitivity blue green R ed ed
Filter Wratten series 6B Wratten series GS-1 Wratten series GS-1
Direct and indirect illuminating types of Darkroom Lights
Cleanliness of the room is important since this is the one place where both intensifying screens and films are exposed to the air. If the counter tops are dirty or contaminated with chemicals, it is easy for the dust to be blown into the cassette and result in damage to the intensifying screens. Counter tops should be of a material that can be easily cleaned. It is also important to prevent contamination or oxidation of the processing solutions. This is most easily done by use of plastic or wooden covers for the processing tanks. Surfaces above the working area should be finished with a white or light -tinted paint in a semigloss or flat finish. A gloss finish sometimes reflects light in an objectionable manner. Surfaces at and below the working area should be finished with a gloss paint for ease of cleaning. Ventilation is important in keeping the darkroom dry and removing objectionable odors. Film stores best at 30% to 50% humidity. Film Processing
Despite the increase use of automatic processors, most radiographs in veterinary radiography are still processed in wet tanks. The discussion on film processing is divided into a section on the use of wet tanks and a section on use of an automatic processor. Developi ng The primary function of the developer is to reduce exposed silver halide crystals to
metallic silver. This is i s done by supplying electrons electrons to the positively charged silver ions that exist in the exposed film. Developer consists of : 1) reducing agents
2) activator 3) restrainer 4) preservative 5) solvent The reducing agents or developing agents most commonly used are hydroquinone and metol in various combinations. combinations. The reducing agents convert the exposed silver halide crystal s into black metallic silver. The activator is sodium carbonate and provides a pH range of 9. 8 to 11.4 11.4. It also swells and softens the emulsion so that the reducing agent can work more effectively. The restrainer is potassium bromide which limits the activity of the reducing agents so that it does not reduce unexposed silver halide crystals. The preservative is sodium sulfite which prevents rapid oxidation of the reducing agents. The solvent is water and dissolves the chemicals. Five minute developing time is recommended for film processing because it permits a reduction of required exposure factors. This could permit use of a shorter exposure time. Use of five minute developing time allows for almost all of the exposed crystals to be converted to metallic silver. Because the chemical reaction has gone to completeness, the time of developing is not as critical and the film may be in the developer solution 4 1/2 to 6 minutes with little difference in film density or blackness. The advantage of this greater degree of freedom in removing the film from the developer solution is obvious. DEVE EVEL LOPER TE ER TE PER ATURE - TIME RELA RELAT TIO SHIP Temperature C0 15.5 18.5 *20 21 24
Temperature F 0 60 65 *68 70 75
Time Minutes 8½ 6 *5 4½ 31/2
*(Optimal temperature-time combination) The process of film developing is a chemical process and is therefore dependent on both time and temperature. Because of this, a constant developer temperature is important in obtaining consistent film density or blackness. Manufacturers recommend a specific temperature for the developer solution they produce. Generally, this is 20°C (68°F). The temperature should not exceed that given in above table. DEVE EVEL LOPER CH ER CHE EMISTRY FOR MANU ANUAL PRO PROC CESSING GENER AL AL FUNC NCT TION R educi educing Agents
CHE CH EMICAL
SPECIAL FU SPE FUNC NCT TION
Metal -- Quickly builds up gray tones in the image.
Developing agents convert exposed silver bromide crystals into black metallic silver.
Hydroquinone---Slowly builds up black tones and contrast in the image. Activator
Sodium Carbonate
Swells Swell s and softens emulsion emulsi on so that reducing agents may work more effectively. Provides required alkalinity for reducing agents
R estrai estrainer
Potassium Potassium Bromide
Restrains reducing agents from causing fog.
Preservative
Sodium Sulfite
Prevents agents
Solvent
Water
Liquid for dissolving chemicals
rapid
oxidation
of
developing developing
High developer temperature causes swelling of the gelatin as well as an increase in chemical activity. The gelatin thickens unevenly and "slips" causing a film artifact called "reticulation". Care must be taken in the placement and removal of the radiograph from the developer solution. That tank is usually small and the film holder can scratch other films in the tank. Gentle film agitation immediately after immersion ensures good mixture of the solution and prevents accumulation of air bubbles on the surface of the film that would prevent good contact of solution with the surface of the film. When the film is removed from the developer bath, there should be a deliberate attempt made to early developer solution over into the rinse bath. This depletes the developer bath of exhausted solution and enables you to replenish the solution. R inse Bath Bath The rinse bath removes developer from the film and diminishes the carry-over of this solution to the fixer tank. Agitation of the film for 30 seconds is adequate to accomplish this. If the bath uses running water, the rinse will be more complete and can be done in a shorter time. It is possible to use an acid bath or stop bath between developer and fixer solutions. This solution is 1.5 1.5% acetic acid and it neutralizes the alkali of the developer and protects the acidity of the fixing bath. In addition, it immediately stops the reduction of silver halide crystals. The pH of the stop bath will be altered by the basic pH of the developer and will require changing to remain effective. Fixing The purpose of the fixer is to convert undeveloped silver bromide crystals left on the film into a soluble compound and dissolve them away. This leaves the silver image as a permanent record. Fixer solution is composed of :
1) a fixing agent
4) a preservative
2) an acidifier
5) a solvent
3) a hardener The fixing agent is sodium thiosulfate (hypo), if the fixer is prepared from a powder, or ammonium thiosulfate if the fixer is prepared from a liquid solution. It acts to clear away the unexposed and undeveloped silver bromide crystals. Sodium thiosulfate forms water soluble complexes in which silver i ons are tightly bound
(AgBr + Na 2 S 203 ~ AgS2 03 + NaBr). NaBr). FIXER CH ER CHE EMISTRY FOR MANU ANUAL PRO PROC CESSING. GENER AL AL FUNC NCT TION Fixing Agent
CHE CH EMICAL
SPE SP ECIAL FU FUNC NCT TION
Sodium or silver bromide
Acidi f ier ier
Acetic or Sulf uric uric Acid
Hardener
Aluminium Ch C hloride or Sulf ide ide emulsion Sodium Sulf ite ite Water
Clears away unexposed Ammonium Thiosul Th iosulf ate ate crystals. Stops development by neutralizing developer. Shrinks and hardens
Preservative Solvent
chemical balance of f ixer ixer Maintains ch Liquid f or or dissolving ch chemicals
The acidifier is acetic or sulfuric acid, and its purpose is to stop development by providing the required acidity to neutralize the developer. The hardener is aluminum chloride or aluminum sulfide and it shrinks and hardens the emulsion. The preservative is sodium sulfite and it maintains chemical balance of the fixers and suppresses sulfur deposition. The solvent is water and serves to dissolve the chemicals. Agitation of the film for 1 5 seconds after being placed in the fixer bath helps to insure equal chemical action and avoid streaks and stains on the film. Wash Washing The purpose of the final washing bath is to wash away the remaining silver complexes and the excess fixing agent. Inadequate washing causes film artifacts that appear later when the image becomes discolored discolored due to residual fixer. The length of washing tim e depends on the frequency with which the water is changing and the number of films being processed. If the water changes completely ten times each hour, the washing time can be 20 minutes. Films can be left in the wash tank overnight without permanent damage. However, the emulsion swells and a longer drying period period is required. required. A longer wash time is required for for non -screen film because of the increased thickness of the film emulsion.
Drying Film drying should be performed in a clean cabinet or room. If a fan is used to circulate air, ensure that a steady stream of air blows over the films. Any dust stirred by the fan will settle on the films and make them feel like sandpaper after they dry. Other problems in film drying are manifested by "water spots" or other drying streaks or marks. It is possible to hasten film drying and avoid some artifacts by use of a wetting agent bath (a surface tension reducer such as a detergent). The film is briefly dipped into a tank of this solution prior to placing in a dryer. These wetting agents agents are commercially available. Film hangers create a sharp point in the corner of each film that cuts badly into the film emulsion when a film is slid over the surface of another film. Therefore, it is important to cut the corners of the radiographs either with scissors or a film corner cutter. Processing Temperature Too often, consideration is given only to the temperature of the developing solution. It is equally important to maintain all of the processing baths in manual processing at about the same temperature to insure the best quality of film processing. R eloadi eloading Cassettes During the time the film processing cycle is occurring, the cassettes are usually reloaded with film. This is somewhat hazardous when performing wet tank processing since you are working back and forth from the wet section of the room to the dry section. It is, therefore, important that you have towels available so you may dry your hands. Cassettes should not be left open on the counter top since it is easy to drop objects and damage the intensifying screens. screens. Load and close the cassettes as quickly as possible.
Use caution when drawing film from the storage box since it is easy to create electricity as the films rub together. Avoid bending the film as it is placed in the cassette. Some film is packed with interleafing paper. This must be removed before placing the film in a cassette. The paper may be left around the film if it is nonscreen film. After the cassettes are reloaded, they should be placed in a specific location in the darkroom. Following completion of the processing of the films, the cassettes can be returned to the radiographic examination room. Hot Weath Weather Processing It is frequently difficult to lower the temperature of freshly prepared solutions being used. Ice may be used as a part of the solvent to lower the temperature of solutions as they are being prepared. Permit the ice to melt completely to determine the temperature of the solution before adding the final solvent.
It is not possible to use ice in the developer or fixer solutions to lower their temperature on a daily basis because of the dilution factor. It is a standard practice of those working in warm climates to place artificial camper's ice such as "Blue Ice" into the solutions to achieve a lower temperature. Do not use artificial cooling agents that are in a metal container that would react chemically with the developer or fixer. Another method of lowering solution temperature is to fill a plastic container with water and freeze. This type of closed carton will not react chemically with the solutions and will not leak water as it melts. It can be reused on a daily basis.
Overnight cooling can be used in clinics where three or five gallon solution tanks are used. Remove a gallon of developer and a gallon of fixer and place them in separate glass containers in a refrigerator overnight. In the morning add the chilled solutions to the warm solutions to bring the working temperatures closer to normal. Satisfactory radiographs can be obtained at developer temperatures between 24° and 27°C ( 75° and 80°F) by adding additional restrainer to the developer. Dissolve 71 gms ( 2.5 ounces) of sodium bicarbonate in 177 cc ( 6 ou nces) of warm water at 27°C (80°F). Add this solution of sodium bicarbonate to each 3 .8 liters (gallon) of diluted developer. Rinsing times should be longer in hot weather because the swollen gelatin holds more alkali. An acetic acid stop bath is also helpful. The fixer may be helped in hot weatherby adding concentrated acetic acid to restore the hardening action of the solution. Keep washing times to a minimum if the wash water temperatures are high. This will avoid damage to the emulsion. Processing Solutions Developer and developer replenishers are available in both powdered and liquid concentrated forms. The liquids are easier to work with since they eliminate the problem of powder settling on counter tops in the darkroom. Solution R eplaceme eplacement Determination of developer and fixer replacement is dependent on the number of films processed and the care exerted in avoiding contamination of the solutions. As a rule, a change in color of developer solution to green or brown suggests aging developer and a need for changing the solution. This change in color is associated with processed film having less density than expected and a tendency for the film to have less contrast because of chemical fogging. Usually developer solutions require changing less often than fixer solutions. This is because the film is dry when first placed into the developer and, therefore, no dilution of the solution occurs. When the film is removed from the developer, a certain amount of developer is carried out with the film, lowering the solution level. This makes it possible to add replenisher solution to maintain a satisfactory level and strength of developer solution.
Activity of the fixer is easier to ascertain because of your ability to evaluate the length of clearing time. The fixer is changed when the clearing time is as long as two to three minutes. It is more difficult to keep the fixer solution at an acceptable strength. This is because each film placed in the fixer brings with it a certain amount of water from the wash tank. The amount of dilution depends on how rapidly you move the film to the fixer tank. Because of this continual addition of water, the level of the fixer solution does not drop at the same rate as the developer and a continual dilution and subsequent weakening of the fixer solution occurs. Combating Algae Filtration of incoming water is basic in eliminating algae from the film processing system. Partial specifications for such a filter are as follows: follows : y y y
l) a mean pore opening of not more than 35 microns, 2) a water flow capacity of at least 19 liters ( 5 gallons) per minute, and 3) a line-pressure drop of less than 0.227 kg (0.5 lb) per 6.45 cm2 (2.6 in2).
Algae can be removed from the walls of the water compartment through repeated scrubbing with a neutral algicide. Diluted acid or laundry bleaches also can be used to clean the tanks and retard algae growth. With each of these procedures the tanks must be washed thoroughly prior to use. A simple method of minimizing the growth of algae is to let the wash tanks dry over a weekend. 14.3 Operating Procedure f or or Manual X -ray Film Processing
In order for manual processing of films to be done correctly a scheme must be followed. The major part of the scheme describes the processing technique for individual films. Monthly duties are also included. Daily
l) stir solutions olution s thoroughly 2) chec heck tem temperature of s of solutions olution s ( C [68°F]) [68°F]) 3) vis visually chec heck for light leak in darkroom darkroo m 4) chec heck for dry towel 5) clean counter tops tops 6) chec heck level of s of solutions olutions 7) chec heck firs first film film carefully for a rough quality control study Individu dividual f ilm ilm 1 ) turn off all white lights light s 2) turn on darkroom darkroom safety light 3) unload cassette ssette and clos lo se cassette ssette lid 4) load film film on hanger 5) set tim timer to 5 minutes inutes scratching adjacen adjacent f ilm) ilm) 6) immer mmers se film fil m in developer, brief agitation (avoid scratching 7) cover developer tank if poss po ssible ible 8) dry hands hands 9) reload cassette ssette 10) rem remove film film from from developer quic quickly when alarm alar m sounds ounds preventing dripping into developer tank 11) drain film fil m into rins rinse tank 12) agitate film fil m in rins rinse water for 30 30 seconds onds 13) lift out of rins rin se water and let drip into rins rin se tank scratching adjacen adjacent f ilm) ilm) 14) immer mmers se film fil m in fixer bath, agitate briefly (avoid scratching 15) rem remove film fil m from from fixer quic quickly after 10 to 20 minutes inutes 16) immer mmers se film fil m in was wash tank depending ding on level of of water 17) rem remove film fil m from from was wash tank after 20-30 minutes inutes (depen replen replenishing ishing) ) sed) 18) immer mmers se in quic quick drying solution (if used) place in drying oven or drying area 19) plac 20) rem remove from from hanger when dry 21 ) cut corners orners 22) plac place in film fil m filling envelope 23) write tec technique and patient identific identification atio n on fil m filing envelope
A Radiog Radiograph f ilm ilm developed by by dark room procedu procedure
