IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

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

IAEA International Atomic Energy Agency

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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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology

Part 15.9: Optimization of protection in radiography

Darkroom evaluation

IAEA International Atomic Energy Agency

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 (D bg ) and the fogged area (D fogged ).

• The extra fog ( D D) equals: D

D = D

fogged

- D

bg

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Darkroom light leakage (V)

Limiting value : in Extra fog:

D

D



0.05 OD 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/QC%20Book.html

American College of Radiology Mammography Quality Control Manual, Reston VA, 1999.

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