Cramér-Rao lower bound of dark-field imaging using a grating interferometer / 中国医学物理学杂志

ABSTRACT

In grating-based phase contrast imaging,the phase stepping technique is commonly utilized for data acquisition and signal retrieval from acquired intensity data.However,the algorithm efficiency with respect to the dark-field retrieval has yet to be sufficiently evaluated.Herein the algorithm efficiency of dark-field retrieval based on Cramér-Rao lower bound is evaluated.The theoretical analysis and numerical results demonstrates that fully efficient algorithm is currently available only for 3-step phase stepping technique,and other techniques with more phase steps are all sub-optimal.Quantitatively,the dependence of the algorithm efficiency on the phase step number and the visibility is investigated.It is shown that the phase stepping technique can nearly approach its theoretical optimal efficiency in the case of a low visibility.With a phase step greater than 5,the algorithm efficiency is only 77.4%in the case of a high visibility.The study can provide some reference for signal-to-noise ratio improvement and potential dose optimization in X-ray and neutron grating-based dark-field imaging.