Investigations of moiréartifacts induced by flux fluctuations in x-ray dark-field imaging  

作　　者：王志立 陈子涵 顾瑶 陈恒 葛昕 Zhi-Li Wang;Zi-Han Chen;Yao Gu;Heng Chen;Xin Ge(Department of Optical Engineering,School of Physics,Hefei University of Technology,Hefei 230009,China;Institute of Biomedical Engineering,Shenzhen Bay Laboratory,Shenzhen 518067,China)

机构地区：[1]Department of Optical Engineering,School of Physics,Hefei University of Technology,Hefei 230009,China [2]Institute of Biomedical Engineering,Shenzhen Bay Laboratory,Shenzhen 518067,China

出　　处：《Chinese Physics B》2023年第3期621-628,共8页中国物理B（英文版）

基　　金：the Natural Science Foundation of China(Grant Nos.U1532113,11475170,and 11905041);Fundamental Research Funds for the Central Universities(Grant No.PA2020GDKC0024);Anhui Provincial Natural Science Foundation(Grant No.2208085MA18).

摘　　要：X-ray dark-field imaging using a grating interferometer has shown potential benefits for a variety of applications in recent years.X-ray dark-field image is commonly retrieved by using discrete Fourier transform from the acquired phasestepping data.The retrieval process assumes a constant phase step size and a constant flux for each stepped grating position.However,stepping errors and flux fluctuations inevitably occur due to external vibrations and/or thermal drift during data acquisition.Previous studies have shown that those influences introduce errors in the acquired phase-stepping data,which cause obvious moiréartifacts in the retrieved refraction image.This work investigates moiréartifacts in x-ray dark-field imaging as a result of flux fluctuations.For the retrieved mean intensity,amplitude,visibility and dark-field images,the dependence of moiréartifacts on flux fluctuation factors is theoretically derived respectively by using a first-order Taylor series expansion.Results of synchrotron radiation experiments verify the validity of the derived analytical formulas.The spatial frequency characteristics of moiréartifacts are analyzed and compared to those induced by phase-stepping errors.It illustrates that moiréartifacts can be estimated by a weighted mean of flux fluctuation factors,with the weighting factors dependent on the moiréphase and different greatly for each retrieved image.Furthermore,moiréartifacts can even be affected by object’s features not displayed in the particular contrast.These results can be used to interpret images correctly,identify sources of moiréartifacts,and develop dedicated algorithms to remove moiréartifacts in the retrieved multi-contrast images.

关 键 词：x-ray imaging dark-field imaging moiréartifacts flux fluctuations 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术] O434.19[自动化与计算机技术—计算机科学与技术]