IAEA International Atomic Energy Agency RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY Part 19.04: Optimization of protection in Mammography Practical exercise IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology

IAEA : Optimization of protection in Mammography2 Overview To be able to apply quality control protocol to mammography equipment To measure the tube voltage accuracy and reproducibility To measure the radiation output and linearity

IAEA International Atomic Energy Agency Part 19.04: Optimization of protection in Mammography Topic 1: kV accuracy and reproducibility IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology

IAEA : Optimization of protection in Mammography4 Accuracy of tube voltage Mammographic image quality and patient dose are dependent on the kilovoltage (kV). A non-invasive tube voltage measurement over the clinical kV-range at 1 kV intervals is necessary

IAEA : Optimization of protection in Mammography5 Reproducibility of tube voltage The reproducibility is measured by repeated exposures at one fixed clinical tube voltage, e.g., 28 kV A digital kVp meter (designed for mammography) is required

IAEA : Optimization of protection in Mammography6 Accuracy and reproducibility of tube voltage Limiting value : Limiting value :Accuracy for kV: < ± 1 kV Reproducibility < ± 0.5 kV Frequency : Frequency :Annually Equipment : Equipment :Digital kVp meter

IAEA International Atomic Energy Agency Part 19.04: Optimization of protection in Mammography Topic 2: Measurement of radiation output - linearity IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology

IAEA : Optimization of protection in Mammography8 Measurements of Radiation Output (I) The tube output is determined by the ratio of entrance surface dose (mGy) and mAs A high radiation output is desirable to ensure that exposure times are sufficiently short to minimize patient movement and discomfort The measurement can be performed either in air or with a phantom

IAEA : Optimization of protection in Mammography9 Measurements of Radiation Output (II) The output is generally measured as a function kV and mAs There are two experimental arrangements used for the determination of the radiation output under clinical conditions. An ionization chamber is positioned at a fixed distance from the focal spot with the beam collimated to the chamber

IAEA : Optimization of protection in Mammography10 Measurements of Radiation Output (III) X-Ray tube Filter Ion chamber Lead sheet Table top FFD Phantom

IAEA : Optimization of protection in Mammography11 Measurements of Radiation Output (IV) In both geometries, a sheet of lead is placed on the top of the table to obtain standard backscatter conditions. The radiation output can be determined under the following operating conditions: Consistency checks for output are made by repeating measurements at constant exposure factors, e.g., 28 kV, 50 mAs

IAEA : Optimization of protection in Mammography12 Measurements of Radiation Output (V) The output is measured at various kVs, keeping the mAs constant. The mAs required for the reference exposure should be used Correct for the distance from the focal spot to the detector. Calculate the output at 1 metre and the output rate at a distance equal to the focus-to-film distance (FFD).

IAEA : Optimization of protection in Mammography13 Measurements of Radiation Output - linearity The linearity of the output with the tube current can be determined by varying the mAs, keeping the kilovoltage constant

IAEA : Optimization of protection in Mammography14 Tube output Limiting value : Limiting value : acceptable: >30  Gy/mAs at 1 m desirable:  Gy/mAs at 1 m acceptable: > 7.5 mGy/s at a distance equal to the FFD desirable: mGy/s at a distance equal to the FFD Frequency : Frequency : Anually and when problems occur Equipment : Equipment : Dosimeter, exposure timer

IAEA Digital systems For systems with digital detectors additional issues need to be considered in order to optimize age quality. Please see the training material on Digital Radiology: ditionalResources/Training/1_TrainingMaterial/ DigitalRadiology.htmhttps://rpop.iaea.org/RPOP/RPoP/Content/Ad ditionalResources/Training/1_TrainingMaterial/ DigitalRadiology.htm : Optimization of protection in Mammography15

IAEA Where to Get More Information 16 European protocol for the quality control of the physical and technical aspects of mammography screening. wnload&view=category&id=1&Itemid=8 American College of Radiology Mammography Quality Control Manual, Reston VA, : Optimization of protection in Mammography