Normalized average glandular dose in molybdenum target-rhodium filter and rhodium target-rhodium filter mammography.

Abstract

To determine the normalized glandular dose (DgN) for molybdenum target-rhodium filter (Mo-Rh) and rhodium target-rhodium filter (Rh-Rh) mammography and compare the average glandular doses (Dg) that resulted with a conventional molybdenum target-molybdenum filter (Mo-Mo) source assembly. X-ray spectra models for Mo-Rh and Rh-Rh were developed and used to calculate DgN values for these target-filter combinations as a function of x-ray tube potential, half-value layer, and breast thickness for three breast compositions. For the average glandular dose comparisons, 50/50 phantoms were imaged for the three target-filter source assemblies at three tube potentials. For the same parameters, DgN values for Mo-Rh and Rh-Rh were higher than for Mo-Mo. At the same voltage, the exposures required to image breast phantoms are substantially lower, and as a result, Dgs are also less with Mo-Rh and Rh-Rh than with Mo-Mo. DgN values presented permit practical evaluations of average glandular doses for Mo-Rh and Rh-Rh mammography. At a given potential, dose savings are realized with Mo-Rh and Rh-Rh source assemblies.