QUALITY CONTROL PROCEDURES for RADIOGRAPHIC PROCESSORS

ITEMS NEEDED

  1. Sensitometer/Densitometer
  2. Thermometer (not mercury)
  3. Fresh box of control film
  4. Monitoring charts

SETTING UP

  1. Reserve a fresh box of film most commonly processed in each processor.
  2. To establish your control values, proceed as follows:
  3. Expose and process a sheet of control film for five (5) consecutive days for each processor.
  4. These results are then averaged to become your "Speed Index," "Contrast Index," and "Gross Fog Index" values for each processor.

EXPOSING AND PROCESSING the CONTROL FILM

  1. Set the sensitometer for the appropriate film spectral sensitivity (blue or green). For single emulsion film, be sure that the emulsion side faces the light-exposing source. For double emulsion film, it is recommended that an exposure be made on each emulsion side.
  2. Wait at least 30 minutes before processing the exposed film to minimize the effects of latent image fading. The processor should run at the recommended temperature.
  3. Read the density of the middle of each step for both exposures using a densitometer. Record the density next to each step.

DETERMINING THE "DAILY SPEED INDEX"

  1. Determine which step has a density closest to 1.20. Designate that step as the "speed step" for all future speed determinations.
  2. Add together the "speed step" densities from each side of the film; divide the result by 2 to obtain the average.
  3. Plot this average speed step density reading on the control chart as the "Daily Speed Index."

DETERMINING THE "DAILY CONTRAST INDEX"

  1. Select the step with the density closest to 2.20 but not higher than 2.20. Select the corresponding step on the other exposure (when using two exposures). Add the two density readings and divide readings and divide by 2 to obtain the average.
  2. Select the step with the density closest to 0.45 but not lower than 0.45. Select the corresponding step on the other exposure (when using two exposures). Add the two density readings and divide by 2 to obtain the average.
  3. Subtract the density value obtained in step 2 from the density value obtained in step 1. This value will be the "Daily Contrast Index."
  4. Plot the "Daily Contrast Index" on the appropriate section of the chart.

DETERMINING THE "DAILY GROSS FOG INDEX"

  1. Select two areas on the processed film which have not been exposed.
  2. Add the two density readings and divide by 2 to obtain the average.
  3. Plot the average as the "Daily Gross Fog Index" on the appropriate section of the chart.

TO EVALUATE "INDEXES," ESTABLISH TOLERANCES AND PLOT TOLERANCE LEVELS

Speed

  • Subtract the density of the speed step for a specific day from the "Daily Speed Index."
  • Density differences of less than 0.15 should be considered to be normal process variations.
  • Density differences of greater than 0.15 require immediate analysis.

Contrast

  • Subtract the contrast value for a specific day from the "Daily Contrast Index" and calculate the difference.
  • Differences less than 0.15 should be considered to be normal process variations.
  • Differences greater than 0.15 require immediate analysis.

Gross Fog

  • Subtract the gross fog value for a specific day from the "Daily Gross Fog Index."
  • Density differences less than 0.03 should be considered to be normal process variations.
  • Density differences greater than 0.03 require immediate analysis.

 

Control Film Crossover

  • When a new box of control film is introduced into the operation, control exposures should be made on both the old and new stock for five days. At the end of five days, compute a new index based on the average of those five days.

Evaluation of the Control Chart

  • A trend exists if a series of consecutive points progresses steadily upward or downward. Such a trend may be a shift taking place slowly and visibly with respect to time.
  • Trends or gross fluctuations should be noted and evaluated. Appropriate action should be taken if necessary.

FINAL COMMENTS

  • It is recommended that the department keep a processor maintenance log for each processor to record all service on the unit. This log can be used to correlate processor service with processor performance.
  • These results were established in seasoned chemistry.
  • When using a low-crossover film for processor control, it is recommended that a simultaneous double-sided exposing sensitometer be used.

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