1. Darkroom Film processor
QC Tests
Darkroom
Film processor
V.G.Wimalasena
Principal
School of Radiography

2. QC tests on film darkroom
Safelight evaluation test
Evaluation of white light leakage and processing area condition
View box quality control test
Evaluation of image duplicators

3. Safelight test Load a film into a cassette in complete darkness
Expose the cassette with step wedge on it , using appropriate exposure factors
Take the film out in the darkroom and keep it on the darkroom bench.
Cover one half of the film with a cardboard.
Switch on the safe light and wait for 2 minutes
Process the film and observe for a defined line which divide the image into two halves.
If there is a fog, measure the optical densities and find the maximum fog (should be < 0.05)

4. Image of step wedge showing safelight fog

5. Light leakage testing and processing area condition
Turn on all the lights surrounding darkroom. Enter the darkroom and switch off all the lights.
After eyes adapt to the dark, check for white light leaks
Turn on overhead light and inspect for foreign objects, dampness etc. on counter tops & film feed tray
Check the film storage conditions and processing chemical tanks.
Check the room temperature.

6. Recommended conditions
Film boxes should be stored vertically
Temperature C
Relative Humidity 30% - 60%
Chemicals must be stored in a well-ventilated area with a temperature C. (for longer periods < 21 0C) and under low lighting.
Films and chemicals should not be stored together. (radioactive isotope of potassium-40 is present in the chemicals and can fog the films)
For films the background radiation should not exceed 7 µR/hr.

7. Viewbox QC Should be cleaned weekly
Intensity should be checked once a year (weekly for mammography)
Use a photometer to measure the brightness. ( luminance or illuminance.)
The standard luminance is 1700 nit. For mammography 3500 nit. (Illuminance should be above 5000 lux)
The colour temperature should be ,000 0K (standard K)
Check for uniformity of the brightness compared to the centre (should be within + 10%).

8. Film Copier QC
Copy a sensitometer film and compare for density difference( ). Should be done weekly
Make a copy of the wire mesh image to check the sharpness level. Should be done monthly
For digital images copy a test pattern image and compare the densities from the similar areas.(+ 0.02)

9. Processor Quality Control
1. Solution temperature
Developer temperature should be checked periodically through out the day. Should not vary C
Fixer temperature should not vary + 30C from that of the developer to avoid reticulation marks.
Use a digital thermometer with a remote probe or a glass, alcohol- filled thermometer

10. 2. Processing time
Change of processing time affect the image contrast, density and the visibility of recorded detail similar to that by the change of temperature.
Should be maintained within + 2% to + 3%
Should be checked daily. Use a stopwatch or digital timer

11. 3. Replenishment rate
If the solutions are not adequately replenished the image contrast and the optical density decreases. Excessive replenishment has the opposite effect to some extent.
The rate should be + 5% of the recommended values.
A film and a graduated cylinder can be used to measure the rate.
Place the cylinder under the opening of the replenisher line.
With the cover of the processor open, feed a 18 x 24 cm film lengthwise, collect the chemical in to the cylinder and measure the volume. Divide the volume by 24 to get the rate in milliliters per centimeter.

12. 4 .Solution pH
Developer solutions function in a pH range of 10 to 11.5.
Fixer solutions should have a pH between 4 and 4.5
pH should be checked daily by using a digital pH meter or pH paper.

13. 5. Specific gravity & proper mixing
The chemicals should be mixed to recommended concentrations. This is given by the specific gravity.
Use a hydrometer to measure the specific gravity
Developer – range from 1.07 to 1.1 and should not vary by more than
Fixer – range from to 1.11 and should not vary by more than

14. 6. Processor cleaning procedures
Dirty processors cannot function properly and is the cause of breakdown.
Proper cleaning procedures should be performed:
Daily – clean all roller racks and look for malfunctioning parts
Monthly - drain the processing tanks, wash inside
Quarterly – drain replenishment tanks and clean
Yearly – use system cleaners to cleen the replenisher and circulation systems

15. 7. Processor maintenance
A proper maintenance schedule must be maintained to ensure continued operation of the film processor. A log of any maintenance procedures should be kept for documentation.
Three types of maintenance
Scheduled:- observations, adjustments and replacement performed daily, weekly, monthly
Preventive:- regular replacement of certain parts
Nonscheduled:- required when a system failure occurs.

16. 8. Processor monitoring
This is accomplished with the performance of daily sensitometric tests which evaluate the performance of processor systems and the chemicals.
Equipment required
Sensitometer or (step wedge and x-ray machine)
Densitometer
Control chart/graph paper
Film

17. Processor monitoring equipment

18. procedure Expose the film in the sensitometer Process the film
Measure and record the densities.
Establish the following indicators of the processor performance.
Base+Fog (BF) – optical density of the clear portion
Speed indicator (or mid-density point) (MD)– optical density 1 above the base+fog and that step number
Minimum density (or lower density) (Dmin)– density & step number closest to 0.25 above B+F.

19. …….Procedure continued
Maximum density (or high density) (Dmax) - the density and the step closest to 2 above B+F density
Contrast indicator or relative density difference (DD) = (Dmax - Dmin )
Plot these values on a control chart.
Repeat the procedure daily and measure the densities of the same step numbers established on the first day
Look for variations and trends.

20. Processor QC trouble shooting