中国物理B ›› 2023, Vol. 32 ›› Issue (3): 38704-038704.doi: 10.1088/1674-1056/ac946a

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

Zhi-Li Wang(王志立)1,†, Zi-Han Chen(陈子涵)1, Yao Gu(顾瑶)1, Heng Chen(陈恒)1, and Xin Ge(葛昕)2   

  1. 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
  • 收稿日期:2022-06-23 修回日期:2022-09-03 接受日期:2022-09-23 出版日期:2023-02-14 发布日期:2023-03-01
  • 通讯作者: Zhi-Li Wang E-mail:dywangzl@hfut.edu.cn
  • 基金资助:
    Project supported by the Natural Science Foundation of China (Grant Nos. U1532113, 11475170, and 11905041), Fundamental Research Funds for the Central Universities (Grant No. PA2020GDKC0024), and Anhui Provincial Natural Science Foundation (Grant No. 2208085MA18).

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

Zhi-Li Wang(王志立)1,†, Zi-Han Chen(陈子涵)1, Yao Gu(顾瑶)1, Heng Chen(陈恒)1, and Xin Ge(葛昕)2   

  1. 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
  • Received:2022-06-23 Revised:2022-09-03 Accepted:2022-09-23 Online:2023-02-14 Published:2023-03-01
  • Contact: Zhi-Li Wang E-mail:dywangzl@hfut.edu.cn
  • Supported by:
    Project supported by the Natural Science Foundation of China (Grant Nos. U1532113, 11475170, and 11905041), Fundamental Research Funds for the Central Universities (Grant No. PA2020GDKC0024), and 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 phase-stepping 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 moiré artifacts in the retrieved refraction image. This work investigates moiré artifacts 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 moiré artifacts 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 moiré artifacts are analyzed and compared to those induced by phase-stepping errors. It illustrates that moiré artifacts can be estimated by a weighted mean of flux fluctuation factors, with the weighting factors dependent on the moiré phase and different greatly for each retrieved image. Furthermore, moiré artifacts 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 moiré artifacts, and develop dedicated algorithms to remove moiré artifacts in the retrieved multi-contrast images.

关键词: x-ray imaging, dark-field imaging, moiré artifacts, flux fluctuations

Abstract: 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 phase-stepping 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 moiré artifacts in the retrieved refraction image. This work investigates moiré artifacts 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 moiré artifacts 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 moiré artifacts are analyzed and compared to those induced by phase-stepping errors. It illustrates that moiré artifacts can be estimated by a weighted mean of flux fluctuation factors, with the weighting factors dependent on the moiré phase and different greatly for each retrieved image. Furthermore, moiré artifacts 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 moiré artifacts, and develop dedicated algorithms to remove moiré artifacts in the retrieved multi-contrast images.

Key words: x-ray imaging, dark-field imaging, moiré artifacts, flux fluctuations

中图分类号:  (X-ray imaging)

  • 87.59.-e
87.64.mf (Dark field) 87.57.cp (Artifacts and distortion) 87.57.N- (Image analysis)