Variable height multi-slit collimator and optimized image reconstruction in a photon-counting system for digital mammography

We have investigated a pre-breast collimator able to operate at variable heights for a photon-counting scanned multi-slit mammography system. A prototype system was built and used to evaluate how different collimator heights combined with optimized collimator slit widths affect dose efficiency and scan time. Moreover, new image construction software which takes into account the sub-pixel shift of each detector line was implemented and evaluated. With maintained scan time a collimator 79 mm above patient support improved dose efficiency for a 100μm disc by 12% and by 22% for a scan time extended by 10%. For image reconstruction and the same disc size a dose efficiency improvement of 32%±9% was measured indicating a higher gain than expected.