Influence of anode/filter material and tube potential on contrast, signal-to-noise ratio and average absorbed dose in mammography: a Monte Carlo study.
The comparative performance of mammographic X-ray systems that use different anode/filter combinations has been assessed for screen-film and digital imaging. Monte Carlo techniques have been used to calculate average glandular dose as well as contrast and signal-to-noise ratio for imaging two test details. Five anode/filter combinations have been studied to establish the potential for dose saving or image quality improvement. For screen-film mammography, it was found that little benefit is gained by changing from a standard 28 kV molybdenum/molybdenum spectrum for breasts up to 6 cm thick. For thicker breasts, where the tube potential for the standard technique might be increased, 20% improvement in contrast can be achieved without dose penalty using molybdenum/rhodium or rhodium/rhodium spectra, whereas dose savings of more than 50% can be attained whilst maintaining contrast using tungsten/rhodium or rhodium/aluminium spectra. In digital mammography, a molybdenum/molybdenum spectrum delivers the lowest dose for a 2 cm breast, but gives the highest dose for thicker breasts. Tungsten/rhodium or rhodium/aluminium spectra provide the lowest doses at greater thicknesses. It is concluded that for screen-film mammography, molybdenum/molybdenum is the spectrum of choice for all but the thickest or most glandular breasts. In digital mammography, an alternative spectrum is preferable for breasts thicker than 2 cm.
Joint Department of Physics, The Royal Marsden NHS Trust and Institute of Cancer Research, Fulham Road, London SW3 6JJ, UK.
D R
DR
Dance
A K
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Thilander
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M
Sandborg
C L
CL
Skinner
I A
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Castellano
G A
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Carlsson
D000535:Aluminum; D001941:Breast Diseases / Q000000981:diagnostic imaging*; D004566:Electrodes; D005260:Female; D006801:Humans; D008327:Mammography / Q000295:instrumentation / Q000592:standards*; D008982:Molybdenum; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011835:Radiation Protection / Q000295:instrumentation; D012238:Rhodium; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis; D014414:Tungsten
D008982:Molybdenum; D000535:Aluminum; D012238:Rhodium; D014414:Tungsten