NORMALIZED AVERAGE GLANDULAR DOSE IN MOLYBDENUM TARGET RHODIUM FILTER AND 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-rhodium 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-ray spectra models for Mo-Rh and Rh-Rh were developed and used to calculate (D) over bar(gN) 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. RESULTS: For the same parameters, (D) over bar(gN) 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, (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 doses for Mo-Rh and Rh-Rh mammography. At a given potential, dose savings are realized with Mo-Rh and Rh-Rh source assemblies.