CONTRAST AND DOSE WITH MO-MO, MO-RH, AND RH-RH TARGET-FILTER COMBINATIONS IN MAMMOGRAPHY

PURPOSE: To study the effect of three mammography target-filter combin ations on contrast and dose. MATERIALS AND METHODS: With screen-film s ensitometry, the contrast of a calcification target embedded in simula ted breast tissue was measured for three target-filter combinations-mo lybdenum-molybdenum (Mo-Mo), molybdenum rhodium (Mo-Rh), and rhodium-r hodium (Rh-Rh)-as a function of x-ray tube potential, breast thickness , and breast composition. The corresponding: average glandular tissue doses were also determined. RESULTS: Contrast and dose decreased with increasing kilovolt peak with all three target-filter combinations. Co ntrast was highest for Mo-Mo and lowest for Rh-Rh for images exposed w ith a low kilovoltage (<29 kVp). For thick or radiographically dense p hantoms, the contrast produced with Mo-Mo was less than or equal to th at produced by the other two x-ray spectra when a higher kilovoltage ( greater than or equal to 29 kVp) was selected. Average glandular dose was greatest for Mo-Mo and lowest for Rh-Rh for all phantom thicknesse s, breast compositions, and tube potentials studied. CONCLUSION: For t he thick or dense breast, the alternative target-filter selections can achieve contrast comparable to or better than that obtainable with Mo -Mo while using a smaller dose.