NORMALIZED AVERAGE GLANDULAR DOSE IN MOLYBDENUM TARGET RHODIUM FILTERAND RHODIUM TARGET RHODIUM FILTER MAMMOGRAPHY

PURPOSE: To determine the normalized glandular dose ((D) over bar(gN)) for molybdenum target-rhodium filter (Mo-Rh) and rhodium target-rhodi um filter (Rh-Rh) mammography and compare the average glandular doses ((D) over bar(g)) that resulted with a conventional molybdenum target- molybdenum filter (Mo-Mo) source assembly. MATERIALS AND METHODS: X-ra y spectra models for Mo-Rh and Rh-Rh were developed and used to calcul ate (D) over bar(gN) values for these target-filter combinations as a function of x-ray tube potential, half-value layer, and breast thickne ss for three breast compositions. For the average glandular dose compa risons, 50/50 phantoms were imaged for the three target-filter source assemblies at three tube potentials. RESULTS: For the same parameters, (D) over bar(gN) values for Mo-Rh and Rh-Rh were higher than for Mo-M o. At the same voltage, the exposures required to image breast phantom s are substantially lower, and as a result, (D) over bar(gs) are also less with Mo-Rh and Rh-Rh than with Mo-Mo. CONCLUSION: (D) over bar(gN ) values presented permit practical evaluations of average glandular d oses for Mo-Rh and Rh-Rh mammography. At a given potential, dose savin gs are realized with Mo-Rh and Rh-Rh source assemblies.