Transcript IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY Part 15.8: Optimization of protection in radiography Practical.

IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
RADIATION PROTECTION IN
DIAGNOSTIC AND
INTERVENTIONAL RADIOLOGY
Part 15.8: Optimization of protection in
radiography
Practical exercise - Grid
IAEA
International Atomic Energy Agency
Contents/Overview
• Subject matter : quality control of
general radiography system
• Step by step procedure to be followed
to assess the grid performance
• Interpretation of results
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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 15.8: Optimization of protection in
radiography
Grid (system factor, homogeneity)
IAEA
International Atomic Energy Agency
What Minimum Equipment is Needed?
• Dosimeter
• Acrylic 20 cm thick
• Densitometer
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Antiscatter grid - grid system factor (I)
• The grid system factor can be measured
with a dosimeter
• Produce two images, one with and one
without the grid system
• Use manual exposure control to obtain
images with an optical density of about 1.00.
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Antiscatter grid - grid system factor
(II)
• The first image is made with the cassette in
the bucky tray (with grid system) and acrylic
on top of the table, and the second with the
cassette on top of the table (without grid
system) and acrylic on top of the cassette
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Antiscatter grid - grid system factor
(III)
• The grid system factor is calculated by
dividing the exposures, corrected for the
inverse square law and optical density
differences
Limiting value :
Grid system factor  3.
Frequency :
Initially and when dose or
exposure time increases
suddenly
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Grid imaging
• To assess the homogeneity of the grid in
case of suspected damage or looking for the
origin of artefacts, the grid may be imaged
by automatic exposure of the bucky at the
lowest position of the AEC-selector, without
any added acrylic
• In general, this gives a good image of the
gridlines
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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
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