Transcript IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY Part 19.05: Optimization of protection in Mammography Practical.

IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
RADIATION PROTECTION IN
DIAGNOSTIC AND
INTERVENTIONAL RADIOLOGY
Part 19.05: Optimization of protection in
Mammography
Practical exercise
IAEA
International Atomic Energy Agency
Overview
• To be able to apply quality control protocol
to mammography equipment
• To measure the Half Value Layer
• Interpretation of results
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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 19.05: Optimization of protection in
Mammography
Beam quality (HVL)
IAEA
International Atomic Energy Agency
Half value layer (HVL)
• The Half Value Layer (HVL) can be assessed by
adding thin aluminium (Al) filters to the X-ray beam
and measuring the attenuation
• Position the detector on top of the breast table
• Place the compression device halfway between
focal spot and detector
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Half value layer (HVL)
• Select 28 kV and an mAs to produce at least
10 mGy and make an exposure
• Position the aluminium filters on top of the
compression paddle and assure that they
intercept the entire radiation field.
• Use the same mAs setting and make an
additional exposure after adding each filter
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X-Ray Tube
HVL Measurement Geometry
Aluminium filter
Diaphragm
~ 300 mm
Compression
paddle
Detector
~ 300 mm
Lead
Breast support
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Half value layer (HVL)
• For higher accuracy (about 2%) a
diaphragm, positioned on the compression
paddle, limiting the exposure to the area of
the detector may be used
• The HVL is calculated by applying the
formula:
X1  ln(
HVL =
IAEA
2 Y2
2
) - X2  ln( Y1 )
Y0
Y0
ln( Y2 )
Y1
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Half value layer (HVL)
Y0 :
the direct exposure reading
(mGy)
Y1 and Y2 : the exposure with added aluminium
thickness of X1 and X2 respectively
Note 1:
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The purity of the aluminium must be 99.0% or
greater. The thickness of the aluminium
sheets should be measured to an accuracy
of 1%
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Half value layer (HVL)
Note 2: For this measurement the output of the
X-ray machine must be stable
Note 3: The HVL for other (clinical)
energies, and other target
materials and filters should also be
measured for assessment of the
average glandular dose
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Half value layer (HVL)
Limiting value : For 28 kV Mo-Mo the HVL
must be over 0.30 mm Al
equivalent
Frequency :
Annually
Equipment :
Dosimeter, 99.0% aluminium
sheets 0.20 and 0.40 mm
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Where to Get More Information
European protocol for the quality control of the
physical and technical aspects of mammography
screening.
http://euref.org/index.php?option=com_phocado
wnload&view=category&id=1&Itemid=8
American College of Radiology Mammography
Quality Control Manual, Reston VA, 1999.
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