Chapter 14 Film Processing-Automatic Processor

 

 

   

 The field of radiography is becoming more automated and automatic processors have evolved from the days of universal manual processing, through the stages of "automatic" hanger processing to the present day hanger less, automatic radiographic machine processor. The modern processor accomplishes the same results obtained with manual processing, except it offers the added benefits of better quality control, faster processing, and it is automatic, compact, and much cleaner in operation.

It is important to remember that an automatic processor is a man-made machine and malfunction is a possibility. As usual, machines break down when you need them most urgently. Therefore, you must consider the type of back-up processing that can be used in the event of a problem. This may consist of a wet tank processing system that is ready to be used at any time . Another possibility is to have an agreement with a nearby veterinary hospital or human hospital to use their film processing facility on an emergency basis. It is better to consider this problem and decide on a solution before the malfunction occurs. It is important to have available the name and address of a competent repair service.

     

 INSTALLATION PLAN.

Plan for the installation of an automatic processor through the wall with a floor drain for the processor and drain for replenisher tanks. The sink is ample for cleaning roller racks. The dryer end of the processor is at the top of the figure.

Automatic film processors:

• l) require little floor space,
• 2) require a much smaller darkroom,
• 3) solve most of the problems of film artifacts experienced in manual processing,
• 4) save considerable time in the darkroom,
• 5) control temperatures of solutions automatically,
• 6) control solution quality automatically, and
• 7) produce a dry radiograph that can be evaluated immediately without the problem of viewing a wet film (Figs. 14-1,14-2).

A problem in upgrading the radiographic portion of a practice is often one of how to locate the darkroom so that it is:

• l) convenient in location,
• 2) occupies a minimal amount of space, and
• 3) is inexpensive in construction.

A new concept in darkroom construction for automatic processors has developed that utilizes a modified revolving darkroom door. These mini-darkrooms are constructed with one cylinder inside the other that provides access to the center as well as making it a light-proof area. The processor is positioned outside the cylinder and is connected by a light-proof tunnel (Fig. 14-3). Thus, all that is in the darkroom is a film cabinet with a work top for loading and unloading cassettes, plus built-in cassette pockets and the entrance to the light-proof tunnel that joins the  

     

  INSTALLATION PLAN.

Plan for the installation of an automatic processor through the wall with a floor drain for processor and sink for cleaning the roller racks. Replenisher tanks are on a movable dolly located near the processor and could be within the darkroom or in a lighted room. A water supply is provided at the tank location. The dryer end of the processor is at the top of the figure.

cylinder to the processor. The units can be made with lead lining or not, however, there is probably no need for lead lining as long as the film stored within the film cabinet is protected. The diameter of the cylinder is 4 feet which means that the total space required is about 4 feet by 7 feet. The total cost of the darkroom is approximately $3,000.00. The darkrooms are equipped with safe lights while all of the electrical, water, and drain requirements for the processor are outside the dark room. These units are available through Consolidated International Corporation, Chicago, Illinois 60609 (800-621 3680). 

14.1 Processor Systems

Much about the automatic processor is not understood or is misunderstood. The automatic processor is composed of systems that perform specific duties and, consequently, can cause specific problems while participating in the overall processing of a radiographic film from the latent image into a diagnostic quality visible image.

Every automatic processor has the same basic systems (Fig. 14-4):

• l) chemistry system
• 2) temperature control system
• 3) transport system
• 4) circulation/filtration system
• 5) replenishment system
• 6) air/dryer system
• 7) electrical system

     

 DRAWING OF MINI-DARKROOM MADE OF REVOLVING DOOR

  Table 14-1

DEVELOPER CHEMISTRY FOR AN AUTOMATIC PROCESSOR

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Table 14-2

FIXER CHEMISTRY FOR AN AUTOMATIC PROCESSOR

 Chemistry System Developer, fixer and wash water are required. The developer converts exposed silver halide crystals to black metallic silver. Phenidone and hydroquinone are the reducing agents with the phenidone

working quickly to build up gray tones while the hydroquinone works more slowly to develop the contrast in the image. Sodium carbonate is the activator and swells and softens the emulsion. Glutaraldehyde functions as a hardener that controls emulsion swelling and partially hardens the emulsion before the film enters the fixer. Potassium bromide functions as a restrainer and prevents the reducing agents from causing fog. The preservative is sodium sulfite which prevents rapid oxidation of the developing agents. Water serves as the solvent for the above chemicals (Table 14-1).

The fixer removes the unexposed silver halide crystals and hardens the film emulsion. Composition of the fixer is the same as that found in manual processing operations. Wash water removes the fixer from the emulsion. Three tanks containing the developer, fixer and wash water are positioned adjacent to each other and form the wet section of the processor (Table 14-2). 

Temperature Control System The processing chemistry of the automatic processor is different from that used in hand processing. The processing times are much shorter and, therefore, processing temperatures must be higher. The higher the temperature, the more active the chemistry becomes. The developer tank has a heating element and a thermostat and controls temperature of developing solutions depending on the processor type between 27° to 33°C (80° to 84°F) for longer time cycles and 32° to 37°C (90° to 94°F) for 90 second cycles.

The temperature of the fixer is usually 2.7° to 5°C (5° to 10°F) higher than that found in manual processing. Temperature of the wash water is controlled by a mixing valve and monitored by a thermometer gauge and is about 2°C below that of the fixer dependent on cycle time. The temperature is lower if the cycle is longer. Some units use a heat exchange system that allows for the use of ambient water 4.5° to 32°C (40° to 90°F3. This feature eliminates the need for a mixing valve and hot water plumbing to the processor. 

   

AUTOMATIC PROCESSOR

Schematic drawings of two types of automatic film processors showing path of film from feed try on left to catch bin on right

Transport System The transport system of the automatic processor is the single feature that most obviously distinguishes this form of film processing from manual processing. The transport system is composed of the l) off-on switches, 2) driver motor, 3) drive shaft, 4) gears, 5) rollers, and 6) drive belts.

The film is placed in a feed tray and moved successively through the wet section into the dry section and into a catch bin. The film may move horizontally or vertically or may make many turns as it travels. Either paired or offset rollers can be used. The rollers are constructed into racks. A separate rack is used to move the film through each of the four major sections of the processor (developer tank, fixer tank, wash tank, and dry section). The rack assemblies are usually driven by a chain called a ladder chain which drives sprockets on the rollers.

The transport system is powered by a drive motor, a processor drive shaft, and a series of cog wheels that transfer the motion to the rollers. The time required for the transfer of the film may be as long as 8 minutes or as short as 90 seconds.

A malfunction in the transport system may be manifested by

• l) film jams,
• 2) abrasion on the film,
• 3) over lapped films,
• 4) cocked films that have turned as they moved through the system,
• 5) unusual noise,
• 6) film retention,
• 7) altered film density, or
• 8) no film movement.

Table 14-3

ADVERTISED PROCESSING TIMES 

Circulation and Filtration System The water system has two functions in the automatic processor: l) to wash the film and 2) to help stabilize the temperature of the processing solutions. A mixing valve may be used to insure that water of the correct temperature is available. After the water flows through the wash tank it goes into a floor drain. Processors are available that use cold water wash and maintain the processor solution temperature in other ways. Filters are installed in the incoming water lines to prevent particulate matter from entering the processor. It is possible to install a standby unit that cuts the flow of water from 6 liters/minute to 1 liter/minute.

 Replenishment System The chemistry is replenished whenever a film is processed. This is easily accomplished in automatic processors with the use of a replenisher pump and an external storage tank filled with developer replenisher.

When the film is fed into the processor a microswitch is activated and through an electronic film sensing circuitry a replenisher pump is activated and replenishes the developer at a calibrated rate. The replenishment rate is determined by the size and number of film processed in a 24 hour period. High volume processors require less replenishment per film than low volume processors.

For instance, for a 90 second automatic processor, processing 24 films or less during a 24 hour period requires a replenishment rate of 95 cubic centimeters per 35 cm length of film travel, 76 to 100 films require a rate of 75 cc's per film, and over 150 films per day requires a rate of only 60 cc's per 35 cm film. The replenishment volume ratio varies primarily because of developer oxidation. Low volume chemistry will oxidize at a faster rate than high volume chemistry; consequently, more replenisher per film is needed.

Replenishment is also required in the fixer section. In automatic processors, the film is full of developer as it enters the fixer section. When the film exits the fixer, it is saturated with fixer solution. Consequently there is little volume change and fixer must be drained and replenished.

Gravity feed replenisher systems are available on some automatic processors precluding the necessity for replenishing pumps.

 Air/Dryer System The components are a blower motor, a blower fan, a heater, and an adequate exhaust system. Thermostatically controlled hot air is directed onto the moving film. Drying temperature is around 40° to 50°C. 

Electrical System Most automatic processors function with 110 volts and can use existing hospital electrical wiring. The processor should be connected to a circuit breaker.

 Processing Times (Table 14-3) When an automatic processor is built, the possible processing times are determined by the manufacturer. It may be possible to alter processing times through mechanical change to the transport system. The times vary from 90 seconds to as long as 9 minutes. In typical 90 second processors, the film spends 22 to 26 seconds in the developer section, 18 to 22 seconds in the fix, 10 to 22 seconds in the wash section and 20 to 40 seconds in the dryer section.

One popular form of automatic processing is the 31/2 minute version. Here the film spends on the average about 50 seconds in the developer section. Because developing time is longer, the developer temperature may be lower. Depending on the type of processor, film and chemistry, the developer can be adjusted within a wide range of temperatures so that it is adequate for the specific system under consideration.

Prior to 31/2 minute processors, 7 minute automatic processing was the most expedient method available. Here the film spent close to 2 minutes in the developing section, and the developer temperature was only slightly above that found in manual processing.

There is little question but that the automatic processor will save time and enable you to do a better job of radiography. You will increase the number of animals examined and make more radiographs per examination.

 Table 14-4

QUESTIONS TO CONSIDER PRIOR TO PURCHASE

AND INSTALLATION OF AN AUTOMATIC FILM PROCESSOR.

• What is the length of the processing cycle?
• What is the processing capacity per hour?
• What is the size of film accommodated?
• What types of film can be processed?
• Is the type of operation standby or continuous?
• Are replenisher tanks supplied? What is their size and capacity?
• Where will they be stored?
• Is a thermostatic water mixing valve needed and if so, is it
• furnished?
• Is the filter and cartridge on the incoming water line supplied?
• What is the water requirement in gallons/minute?
• Does the unit use hot or cold water?
• What are the ducting requirements for the dryer section?
• What are the floor space requirements?
• Is the unit installed through a hole in the wall or is it contained
• Where will they be stored?
• What are the drain requirements? If draining into an open sink, will
• there be a problem of odor?
• Is the replenisher system pump or gravity?
• Does the unit require an electrical capability not provided by a
• standard electrical outlet?
• Can you easily remove the transport system for cleaning? Where will
• you clean the racks?
• Is there a signal advising correct processing temperature?
• Can you change the length of the processing cycle?
• Can a daylight loader be installed if necessary?
• What type of quality control program will be instituted?
• What is the cost of the sensitometer and densitometer used in the
• quality control program?

Diagnosis will be easier since the quality of the radio graphs is more consistent and the number of artifacts is less. You will be evaluating dry films and be able to read them more closely. Still, purchase of an automatic processor can be made only after careful evaluation of the size of the radiology case load because of the high cost of the unit. 

Standby Controls Automatic standby controls for automatic processors reduce wear on the unit and save money in operating costs. This is a result of reducing power consumption, reducing water consumption, and reducing the need to heat water. The standby control maintains the unit in a ready condition but keeps solution temperatures at a lower level. A switch is activated when film processing is anticipated, and within 10 to 15 minutes the processor is ready to handle films. Use of a standby control such as this must be recommended for hospitals that need to be ready to process film at all times. The switch can be pushed prior to radiographing the animal. The solutions will have reached the proper temperature by the time you are ready to process the films. 

Quality Control System

Automatic processing of medical x-ray film is becoming increasingly common. It should not be assumed that these units will solve all problems relative to film processing and guarantee a perfect radiograph each time. A recent study on the base-fog densities of films developed in several automatic processors showed considerable variation between units and between individual processors from day to day. Therefore, to provide radiographic images of consistent quality, it is recommended that in addition to performing routine maintenance tasks, periodic monitoring of system performance should be undertaken.

The quality control system described below is not practical for the average clinic. However, it seemed appropriate to describe how a program might be constructed. There may be parts of the system that can be applied to your particular situation that should certainly be lifted from the total program. The other reason for studying the method of quality control is to become more familiar with the types of problems that such a system can evaluate. Knowing more about how to evaluate your processor problems will enable you to spot the problems more quickly and more accurately.

A basic photographic processor quality control system is established to consistently produce the same density and contrast on films that receive the same sensitometric exposure and therefore eliminate this important variable in the production of the radiograph.

A sensitometer is a device that is designed to provide a repeatable known exposure to photo-sensitive materials (film) through a step wedge attenuator. An inexpensive sensitometer costs in the range of $300.

The densities can be compared visually with other samples, or numerical density values can be determined by means of a densitometer. The densitometer is a device that provides measurements of the optical density of photographic materials after they have been processed and dried. The densitometer may be a visual instrument in which case the technician is required to compare adjacent densities or the unit may possess a meter or digital readout. The cost of these units is in excess of $200.

Control charts are utilized to record data on a daily basis. Tolerances can be established and drawn on the charts. If readings exceed the upper or lower control limits, excessive deviations from normal processing will be readily apparent.

The following program is done once and establishes the base levels of density expected on your radiograph.

• l. Drain the chemicals from the processor and flush with fresh water. Do not use cleaners in the processor at this time.
• 2. Fill the fixer tank with fresh fixer.
• 3. Flush the developer tank with fresh water and fill the developer tank with fresh developer.
• 4. Set the temperature of the processor at the level recommended .
• 5. Adjust replenishment rates to the recommended level.
• 6. Process the equivalent of 50 large films per gallon of developer.
• 7. Expose and process sensitometric films.
• 8. Zero and calibrate the densitometer, read all steps and average the individual step densities for the films. Make the reading in the center of the density strip.
• 9. Select those steps that have an average density of approximately 1.00 and 2.00 and the "base plus fog" level for the film. These will be the steps used on the daily evaluations. The density of 1.00 (0.9-1.2) above fog is referred to as the medium or mid-density or speed index. The difference between the lowest density and the highest density patches is called the density difference or contrast index.
• 10. Upper control limits and lower control limits can be drawn on the charts using control limits of + 0.15 to 0.20 for the density difference or contrast index and for the medium density or speed index. The limit for base fog plus fog level can be + 0.05.

Having established the control chart with the limits drawn on it, the daily quality control procedure is noted to be much more simple.

• 1. Use start up procedures for the processor.
• 2. Allow the temperature to stabilize.
• 3. Record solution temperatures and replenishment rates.
• 4. Use clean-up film sheets to remove residue from the racks and check for scratches.
• 5. Expose a sensitometric control strip.
• 6. Read the speed index and the contrast index plus the "base plus fog" level.
• 7. If all data falls within the upper and lower control limits the processor is functioning well and no further action need be taken.
• 8. If part or all of the data fall on or exceed the upper or lower control limits the following actions should be taken: 
  • a. process another pair of control strips to confirm your findings;
  • b. check developer temperature, replenishment rates, water flow, water temperature, transport time, recirculation pumps and filters;
  • c. take corrective action;
  • d. after correcting the situation, process another pair of control strips.

It is assumed that in the absence of detectable problems in radiographic quality, a control method could be conducted on a weekly or bi-weekly basis instead of a daily basis. Quality assurance programs help to ensure that you are constantly producing the same photo graphic density and contrast on radiographs receiving the same sensitometric exposure. The processor quality control test may indicate a problem prior to your being able to detect the problem by examination of the radiograph. This is the reason that a daily control check is of particular value. 

14.3 Operating Procedure for Automatic Processor 

Daily start-up (may need to position processor cover prior to start-up)

• I ) close wash tank drain valve
• 2) turn on water supply
• 3) adjust temperature of water supply unless cold water processor
• 4) turn on main disconnect switch and switches on electrical control panel
• 5) process films to clean cross-over rollers
• 6) check replenishment rates
• 7) check operation of racks and crossovers
• 8) check seating and operation of the squeegee crossover assembly
• 9) check developer temperature
• 10) check dryer temperature if possible
• 11) replace processor cover

 Prior to processing each case

• l) check water temperature if possible
• 2) check developer temperature
• 3) check replenishment solution flow
• 4) check cover for tight closure 

Daily Shut-down

• I ) clear processor of all films
• 2) remove all crossover assemblies and rinse them with warm water. Use a soft brush to remove any formed deposits.
• 3) wipe off all rack rollers above the solution level
• 4) wipe off the feed rollers
• 5) turn off all electrical switches and main disconnect switch
• 6) turn off water supply
• 7) open wash tank drain valve
• 8) open cover for ventilation

 Weekly maintenance

• l) remove all roller racks and crossover assemblies and scrub with Scotch-Brite or similar type cleaning pad
• 2) rotate the rack by hand to be sure that all rollers turn freely. Adjust the chain if any sign of roller hesitation is noted.
• 3) check the turn around assembly at the bottom of the rack to be sure its rollers are parallel with the vertical path rollers of the rack.
• 4) with pumps turned on, observe the surface of the solution tanks to check for recirculation
• 5) examine solution tanks for foreign matter while racks are removed
• 6) check all crossover and rack gears for proper engagement when racks and crossovers are reinstalled
• 7) check squeegee crossover assembly for proper seating
• 8) rinse air intake filter assembly with warm water
• 9) inspect dryer air tubes and clean if necessary. 

Monthly maintenance (bimonthly, dependent on use)

• l) drain developer and fixer tanks
• 2) scrub, rinse and refill tanks 

Biannual maintenance (systems cleaner service is usually performed by a qualified service technician)

• l) drain all tanks and lines
• 2) use systems cleaner to remove all buildup of chemicals in the lines, tanks and on rollers
• 3) refill tanks
• 4) change developer recirculation filter 

References

• Ferguson, J. P. and Schadt, W. W.: Variability in the Automatic Process ing of Medical X-ray Film. Dept. of HEW, Public Health Service, Bureau of Radiological Health, 1970.
• Gray, J. E.: Light Fog on Radiographic Films: How to Measure it Properly. Radiol. 115:225-7,1975.
• Gray, J. E.: Photographic Quality Assurance in Diagnostic Radiology, Nuclear Medicine, and Radiation Therapy; Vol. 1, The Basic Principles of Daily Quality Assurance (HEW Publication (FDA) 76 8043); Vol. 2, Photographic Processing, Quality Assurance, and the Evaluation of Photographic Materials (HEW Publication, (FDA) 77-8018); Bureau of Radiological Health, Rockville, Mary land .
• Gray, J. E. and Haus, A. G.: Protocol for Basic Photographic Processor Quality Control. Applied Radiology, pp. 115 - 8, January/ February, 1977.
• Gray, J. E. and Haus, A. G.: Lecture RSNA-1978.
• Hall, C. L.: Economic Analysis of a Quality Control Program, Proceed ing of the SPIE Technical Symposium Entitled Application of Optical Instrumentation in Medicine Vl, September 1977, Boston, MA.
• Haus, A. G.: What the Radiologist Wants from a film Processor, A.C.R./ B.R.H. 2nd Image Receptor Conference, Washington, D.C., March, 1977.
• Haus, A. G., Rossmann, K., Vyborny, C., Hoffer, P. and Doi, K.: Sensitometry in Diagnostic Radiology, Radiation Therapy and Nu clear Medicine. Journal of Applied Photographic Engineering, 3:114-24, 1977.
• Lavvrence, D. J.: A Simple Method of Processor Control. Medical Radiography and Photography 49:2-6 and 28,1973.
• Poznanski, A. K. and Smith, L. A.: Practical Problems in Processing Control. Radiol. 90:135-8,1968.