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IAEA International Atomic Energy Agency RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY Part 19.10: Optimization of protection in mammography Practical exercise IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology

RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology. RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY. Part 19.10: Optimization of protection in mammography Practical exercise. Contents. - PowerPoint PPT Presentation

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Page 1: RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

IAEAInternational Atomic Energy Agency

RADIATION PROTECTION INDIAGNOSTIC AND

INTERVENTIONAL RADIOLOGY

Part 19.10: Optimization of protection in mammography

Practical exercise

IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology

Page 2: RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

IAEA 19.10: Optimization of protection in mammography 2

Contents

• To be able to apply quality control protocol to mammography equipment

• To measure the AEC performance • Optical density control setting • Short term reproducibility• Long term reproducibility• Object thickness compensation• Tube voltage compensation

Page 3: RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

IAEAInternational Atomic Energy Agency

Part 19.10: Optimization of protection in mammography

AEC

(Automatic Exposure Control)

IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology

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IAEA 19.10: Optimization of protection in mammography 4

AEC system

• The performance of the Automatic Exposure Control (AEC) system can be described by the reproducibility and accuracy of the automatic optical density control under varying conditions, e.g., different object thicknesses and tube voltages.

• An essential prerequisite for these measurements is a stable operating film-processor and the use of the reference cassette.

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IAEA 19.10: Optimization of protection in mammography 5

Equipment needed

• PMMA: plates 20 x 300 x 300 mm

• Densitometer

• Reference cassette

• Dosimeter

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IAEA 19.10: Optimization of protection in mammography 6

Optical density control setting: central value and difference per step

• Produce exposures with a breast equivalent phantom material with varying positions of the optical density control selector

• A target value for the mean optical density should be established according to local preference.

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IAEA 19.10: Optimization of protection in mammography 7

OD control setting: central value and difference per step

Limiting valueLimiting value : : The film density (base + fog included) at the reference point should remain within ± 0.20 in density of the target value.

Target value is typically in the range: 1.30-1.80 (base + fog included)

The desirable control step difference is 0.10; 0.20 per step is acceptable

Adjustable range > 1.00

Frequency Frequency :: Step size: every six monthsCentral density: daily

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IAEA 19.10: Optimization of protection in mammography 8

(AEC) - Short term reproducibility

• Position the dosimeter in the x-ray beam but without covering the AEC-detector.

• The short term reproducibility of the AEC system is the deviation of the radiation dose for five exposures with a breast equivalent phantom

Limiting value : The deviation must be < ± 5%; desirable would be < ± 2%.

Frequency : Every six months

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IAEA 19.10: Optimization of protection in mammography 9

(AEC) - Long term reproducibility

• The long term reproducibility can be assessed from the measurement of the film optical density resulting from the exposure of a breast equivalent phantom

Limiting value : < ± 0.20 optical density acceptable;

< ± 0.15 desirable Frequency :Daily

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IAEA 19.10: Optimization of protection in mammography 10

Object thickness compensation (AEC)

• Compensation for object thickness is measured by exposures of PMMA plates in the thickness range 20 to 40 mm, using the clinical setting for the AEC

Limiting value : All density variations must be

within ± 0.20 of the target density.Desirable : ± 0.15 Frequency : Weekly

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IAEA 19.10: Optimization of protection in mammography 11

Tube voltage compensation (AEC)

• Compensation for tube voltage is measured over the clinical range of kV, filters, and target materials

Limiting value : All density variations must be within ± 0.15 of the target

density; Desirable : ± 0.10

Frequency : Every six months

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IAEA

Where to Get More Information

15.3: Optimization of protection in radiography 12

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.