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British Journal of Radiology (2006) 79, 981-990
© 2006 British Institute of Radiology
doi: 10.1259/bjr/55334425
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Optimal beam quality selection in digital mammography

K C Young, PhD 1 J M Oduko, PhD 1 H Bosmans, PhD 2 K Nijs, BSc 2 and L Martinez, BSc 3

1 National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford GU2 7XX, UK, 2 UZ Gasthuisberg, Department of Radiology, Herestraat 49, B-3000 Leuven, Belgium, 3 Department of Physics, The Royal Marsden NHS Trust, London SW3 6JJ, UK


Figure 1
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  		Figure 1. Noise components as a function of linearized pixel values for the CR system. The data points come from the background regions of interest used to measure the contrast-to-noise ratio at all the thicknesses of PMMA, each of the beam qualities tested and the different dose levels.

 

Figure 2
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  		Figure 2. Noise components as a function of pixel values for the DR system. The data points come from the background regions of interest used to measure the contrast-to-noise ratio at all the thicknesses of PMMA, each of the beam qualities tested and the different dose levels.

 

Figure 3
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  		Figure 3. Contrast for 0.2 mm aluminium for different breast thickness and beam quality using the CR system. (Error bars indicate 95% confidence limits).

 

Figure 4
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  		Figure 4. Contrast-to-noise ratio (CNR) vs mean glandular dose (MGD) for a simulated 75 mm thick breast for the CR system. There are no data for the 25 kV Mo/Mo combination as the backup timer prevented exposures of the 60 mm thickness of PMMA. (Error bars indicate 95% confidence limits).

 

Figure 5
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  		Figure 5. Mean glandular dose for the CR system interpolated for a contrast-to-noise ratio (CNR) of 8.5. (Error bars indicate 95% confidence limits).

 

Figure 6
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  		Figure 6. Contrast-to-noise ratio (CNR) vs mean glandular dose (MGD) for a simulated 75 mm thick breast for the DR system. There are no data for the 25 kV Mo/Mo combination as the backup timer prevented exposures of the 60 mm thickness of PMMA. (Error bars indicate 95% confidence limits).

 

Figure 7
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  		Figure 7. Mean glandular dose for the DR system interpolated for a CNR of 12.(Error bars indicate 95% confidence limits).

 

Figure 8
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  		Figure 8. Contrast-to-noise ratio for the DR system using a fixed pixel value of 900. (Error bars indicate 95% confidence limits).

 




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