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

•
To be able to apply quality control protocol to mammography equipment
•
To measure the Half Value Layer
•
Interpretation of results
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19.05 : Optimization of protection in Mammography 2

IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Beam quality (HVL)
IAEA
International Atomic Energy Agency

•
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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19.05 : Optimization of protection in Mammography 4

•
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
Aluminium filter
HVL Measurement Geometry
Diaphragm
Compression paddle
Detector
Lead
Breast support
IAEA
19.05 : Optimization of protection in Mammography
~ 300 mm
~ 300 mm
6

•
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:
HVL =
X
1
 ln(
2 Y
Y
0
2
) X ln(
Y
2
Y
1
)
2
 ln(
2 Y
1
)
Y
0
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Y
0
: the direct exposure reading
(mGy)
Y
1 and Y
2
: the exposure with added aluminium thickness of X
1 and X
2 respectively
Note 1 : 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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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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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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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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