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RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

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. Overview.

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RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

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  1. IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology RADIATION PROTECTION INDIAGNOSTIC ANDINTERVENTIONAL RADIOLOGY Part 19.05: Optimization of protection in Mammography Practical exercise

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

  3. IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology Part 19.05: Optimization of protection in Mammography Beam quality (HVL)

  4. 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 19.05 : Optimization of protection in Mammography

  5. 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 19.05 : Optimization of protection in Mammography

  6. HVL Measurement Geometry X-Ray Tube Aluminium filter Diaphragm Compression paddle Detector Lead Breast support ~ 300 mm ~ 300 mm 19.05 : Optimization of protection in Mammography

  7. 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: 19.05 : Optimization of protection in Mammography

  8. 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: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% 19.05 : Optimization of protection in Mammography

  9. 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 19.05 : Optimization of protection in Mammography

  10. 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 19.05 : Optimization of protection in Mammography

  11. 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_phocadownload&view=category&id=1&Itemid=8 American College of Radiology Mammography Quality Control Manual, Reston VA, 1999. 15.3: Optimization of protection in radiography

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