Effect of using tungsten-anode X-ray tubes on dose and image quality in full-field digital mammography

Dose and image quality have been evaluated for two types of digital mammography system which have X-ray tubes with tungsten anodes, the Siemens Novation and the Hologic Selenia. For each system, contrast-to-noise ratio and threshold contrast measurements were made. The results were used to determine the optimum exposure settings for each system to meet the achievable image quality standard of the European Guidelines. For the Selenia systems, dose savings between 9% and 52% were achieved by using a tungsten-target tube, for PMMA thickness ranging from 20 to 70mm. For the Novation, for the same range of PMMA thickness simulating breasts, the dose saving was 10% to 50% when using a W/Rh rather than Mo/Mo target-filter combination. When comparing W/Rh with Mo/Rh for the Novation, a more modest dose reduction ranging from 4% to 18% was achieved.