Glandular breast dose for monoenergetic and high-energy x-ray beams: Monte Carlo assessment

Abstract

PURPOSE: To extend the utility of normalized glandular dose (D(gN)) calculations to higher x-ray energies (up to 120 keV) and to provide the tools for investigators to calculate D(gN) values for arbitrary mammographic and x-ray spectra. MATERIALS AND METHODS: Validated Monte Carlo methods were used to assess D(gN) values. One million x-ray photons (1-120-keV, in 1-keV increments) were input to a semicircular breast geometry of thicknesses from 2 to 12 cm and breast compositions from to 0% to 100% glandular. D(gN) values for monoenergetic (1-120 keV) x-ray beams, polyenergetic (40-120 kV, tungsten anode) x-ray spectra, and polyenergetic mammographic spectra were computed. Skin thicknesses of 4-5 mm were used. RESULTS: Th calculated D(gN) values were in agreement within approximately 1%-6% with previously published data, depending on breast composition. D(gN) tables were constructed for a variety of x-ray tube anode-filter combinations, including molybdenum anode- molybdenum filter, molybdenum anode-rhodium filter, rhodium anode-rhodium filter, tungsten anode-rhodium filter, tungsten anode-palladium-filter, and tungsten anode-silver filter. D(gN) values also were graphed for monoenergetic beams to 120 keV and for general diagnostic x-ray beams to 120 kV. CONCLUSION: The tables and graphs may be useful for optimizing mammographic procedures. The higher energy data may be useful for investigations of the potential of dual-energy mammography or for calculation of dose in general diagnostic or computed tomographic procedures.