RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

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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

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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

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What Minimum Equipment is Needed?

• Opaque material to cover film
• 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, e.g., door frames, ceiling, around
  processor and pass box, etc.
• Turn the safelights on and perform a visual check
  that all safelights are in good working order
  (filters not cracked)

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Darkroom light leakage (II)

• To measure the extra fog as a result of any light
  leakage or other light sources, pre-expose a film
  to an optical density of 1.20
• Always measure the optical density differences in
  a line perpendicular to the tube axis to avoid
  influence of the heel effect
• Use the fastest speed film normally handled in
  the dark room. If films of different spectral
  sensitivity are used in the darkroom, the test
  must be carried out with each type.

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Darkroom light leakage (III)

• Assure that all of the safelights and control
  panel lights in the darkroom are turned on.
• Open the cassette with pre-exposed film and
  position the film (emulsion up) on the
  (appropriate part of the) workbench
• Cover half the film with opaque material and
  expose for two 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 0.05 OD in 2
minutes Frequency Initially, every six months
and when light leakage is suspected
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Where to Get More Information
Quality Control in Diagnostic Imaging, Gray JE,
Winkler NT, Stears J, Frank ED. Available at no
cost. http//www.diquad.com/QC20Book.html Ameri
can College of Radiology Mammography Quality
Control Manual, Reston VA, 1999.