Microdosimetric characterisation of 28 kVp Mo/Mo, Rh/Rh, Rh/Al, W/Rh and Mo/Rh mammography X ray spectra.
Microdosimetric characteristics of 28 kVp mammography X ray spectra were studied for several target/added filtration combinations (Mo/Mo, Rh/Rh, Rh/Al, W/Rh, Mo/Rh). Monte Carlo techniques were used to model X ray production from mammography units and to calculate distributions of absorbed dose and energy imparted in breast tissue. The results show that the dose averaged lineal energy is about 5.0 keV.micron-1, about 25% higher than for general diagnostic imaging X ray spectra. Significant differences in lineal energy between the five X ray qualities were noted, with the highest value for the commonly used Mo/Mo combination. Spectral hardening with depth in the tissues causes a 5% decrease in lineal energy over 5 cm. No significant differences were found for the different tissue compositions.
Physics Department, Royal Marsden NHS Trust & Institute of Cancer Research, Fulham Road, London SW3 6JJ, UK. frank.verhaegen@npl.co.uk
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Castellano
D001940:Breast / Q000528:radiation effects; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008327:Mammography / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D009010:Monte Carlo Method; D017785:Photons; D011786:Quality Control; D014965:X-Rays