Differential phase-contrast tomosynthetic experimental system with weakly coherent hard X-rays

Abstract

Hard X-ray phase-contrast imaging can provide high sensitivity of weakly absorbing low-Z objects in medical and biological fields. Grating-based differential phase-contrast (DPC) method which relies on Talbot self-imaging effect have been paid more attention because it can work with conventional X-ray tube and show great potential for clinic use. Meanwhile tomosynthesis as a 3D reconstruction method is especially useful in mammography where low does is necessary. In this paper, an phase-contrast tomosynthetic experimental system is implemented based on the differential phase contrast imaging method according to moiré deflectometry (named MD-DPC method) with weakly coherent hard X-rays. The source grating of former grating-based method can perhaps be removed and the energy utilization efficiency of the X-ray tube is increased. The effectiveness of MD-DPC method is proved by actual experiments. In our phase-contrast tomosynthetic experimental system, the x-ray tube and the detector is stationary while the sample is rotated on a rotation stage, which is equivalent to conventional linear tomosynthesis. However, for phase contrast image, the refraction-angle is the line integral of differentials of refractive index decrement in the sample along the beam path whose vector direction is vary as the tomosynthetic projection direction changes, so refraction-angle projections can’t be simply added up like scalar quantities as in conventional tomosynthesis. A mapping method is adopted here to map each refraction-angle projection to the same direction and then refraction-angle tomosynthetic images can be implemented by adopting the shift-and-add approach. Our experimental system is validated and phase-contrast tomosynthesis based MD-DPC would be considered as a promising imaging method for mammography to enhance the contrast of early cancer tissues in the near future.