Transcript RADIATION PROTECTION IN DIAGNOSTIC RADIOLOGY

IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
RADIATION PROTECTION IN
DIAGNOSTIC AND
INTERVENTIONAL RADIOLOGY
Part 16.4: Optimization of protection in
fluoroscopy
Practical exercise
IAEA
International Atomic Energy Agency
Overview / Contents
• To become familiar with quality control
tests in fluoroscopy
• To measure the low contrast resolution
and noise according to the suggested
procedures
• Interpretation of results
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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 16.4: Optimization of protection in
fluoroscopy
Low contrast resolution and noise
IAEA
International Atomic Energy Agency
Low contrast resolution and noise
Purpose :
• to measure the low contrast resolution and the
influence of noise on low contrast detectability
Equipment :
• image quality phantom (Leeds phantom)
• 2 mm Cu filter
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Low contrast resolution
• The low contrast resolution determines the size of
detail that can be visibly reproduced when there is
only a small difference in density relative to the
surrounding area
• Low contrast resolution is considerably limited by
noise.
• The perception threshold in relation to contrast and
detail size can be determined, for example, by
means of a contrast-detail curve.
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Leeds Fluoroscopy Phantom
Noise and contrast loss
Incorporates:
• 19 discs, each 11 mm
diameter, of different
x-ray contrasts.
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Leeds Fluoroscopy Phantom
Noise and contrast loss
Typical fluoroscopic
image of the test
object. View the
small circles at
center and
• count the number
of visible circles
Images from:
http://www.leedstestobjects.com/modules/products/pr
oduct_setup/file_library/SFS%20SET%20product%20
specifications.pdf
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Leeds Fluoroscopy Phantom
Noise and contrast loss
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Noise and contrast loss
Interpretation of results
The threshold contrast is determined by the detail
which can only just be detected. The threshold
contrast of a modern system in average adjustment
should not be greater than the following values:
Field size
diameter
cm
30 - 35
22 - 25
15 – 18
IAEA
Threshold Contrast
%
3.3
2.7
2.3
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Leeds Fluoroscopy Phantoms
Overall Imaging Performance
Incorporates:
• 108 discs in 12 groups
of different diameters;
in each group there
are 9 discs of different
X-Ray contrasts.
• Is used to assess the
threshold-contrast
detail-detectability.
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Leeds Fluoroscopy Phantoms
Overall Imaging Performance
Typical
fluoroscopic
image of the
test object.
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Leeds Fluoroscopy Phantoms
Overall Imaging Performance
Interpretation of results
Data are plotted as
a function of detail
diameter.
Threshold
detection index is
defined as
H (A) = [C(A) A]-1
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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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