RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

1
RADIATION PROTECTION INDIAGNOSTIC
ANDINTERVENTIONAL RADIOLOGY
IAEA Training Material on Radiation Protection in
Diagnostic and Interventional Radiology

• Part 15.9 Optimization of protection in
  radiography
• Practical exercise - Darkroom evaluation

2
Overview / Objectives

• Subject matter Darkroom evaluation
• Step by step procedure to be followed to
  implement the considered QC test
• Darkroom light leakage
• Darkroom safelight
• Interpretation of results

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Part 15.9 Optimization of protection in
radiography
IAEA Training Material on Radiation Protection in
Diagnostic and Interventional Radiology

• Darkroom evaluation

4
What Minimum Equipment is Needed?

• Film cover
• Densitometer

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Darkroom light leakage (I)

• Remain in the darkroom for a minimum of five
  minutes with all the lights, including the
  safelights, turned off
• Ensure that adjacent rooms are fully illuminated
• Inspect all those areas likely to be a source of
  light leakage

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Darkroom light leakage (II)

• To measure the extra fog as a result of any light
  leakage or other light sources, a pre-exposed
  film of about 1.2 OD is needed
• Always measure the optical density differences in
  a line perpendicular to the tube axis to avoid
  influence of the heel effect

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Darkroom light leakage (III)

• Open the cassette with pre-exposed film and
  position the film (emulsion up) on the
  (appropriate part of the) workbench
• Cover half the film and expose for four minutes.
• Position the cover also perpendicular to the heel
  effect to avoid the influence of this
  inhomogeneity in the measurements

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Darkroom light leakage (IV)

• Measure the optical density difference of the
  background (Dbg) and the fogged area (Dfogged).
• The extra fog (DD) equals
• DD Dfogged - Dbg

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Darkroom light leakage (V)
Limiting value Extra fog DD 0.02 OD in 4
minutes Frequency Initially, every six months
and when light leakage is suspected
10
Darkroom safelight (I)

• Perform a visual check that all safelights are in
  good working order (filters not cracked)
• To measure the extra fog as a result of the
  safelights, repeat the procedure for light
  leakage but with the safelights on
• Make sure that the safelights were on for more
  than 5 minutes to avoid start-up effects

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Darkroom safelight (II)

• Limiting value Extra fog DD 0.10 OD in 4
  minutes.
• Frequency Initially, every six months and
  every time the darkroom environment has
  changed