arXiv:2412.15513physics.opticseess.IV2024-12被引 4

用相位信息自动优化暗场成像的不稳定性问题,提升重建精度。

Stabilizing Laplacian Inversion in Fokker-Planck Image Retrieval using the Transport-of-Intensity Equation

  • 利用传输强度方程的稳定相位解作为参考,自动优化正则化参数
  • 在同步辐射四杆样品数据上成功还原相位与暗场图像,避免人工调参
  • 方法可推广至其他基于福克-普朗克方程的成像算法,适用性广

X射线衰减、相位和暗场图像提供互补信息。不同实验技术可捕获这些对比机制,相应图像可通过多种理论算法恢复。我们先前提出的多模态固有散斑追踪(MIST)算法适用于基于散斑的X射线成像(SBXI)数据的多模态图像重建。该方法基于X射线福克-普朗克方程,需对导数算子进行反演,常存在数值不稳定性。此类不稳定性可通过正则化技术(如Tikhonov正则化)缓解,但其结果对正则化参数高度敏感,需谨慎选择。本文提出一种自动化迭代算法,用于优化最新版MIST中逆拉普拉斯算子的正则化,解决傅里叶空间原点附近的不稳定性问题。算法利用SBXI中来自传输强度方程的稳定相位解作为可靠真值,指导更复杂的福克-普朗克基算法(含暗场信号)。我们在同步辐射采集的四杆样品SBXI数据集上应用该算法,成功实现相位与暗场图像的最优重建,消除了繁琐且主观的正则化参数选择过程。所提优化算法使MIST更易用,无需手动调参。我们预期该方法也可应用于其他基于福克-普朗克方程的图像重建方法。

原文摘要 · Abstract (English)

X-ray attenuation, phase, and dark-field images provide complementary information. Different experimental techniques can capture these contrast mechanisms, and the corresponding images can be retrieved using various theoretical algorithms. Our previous works developed the Multimodal Intrinsic Speckle-Tracking (MIST) algorithm, which is suitable for multimodal image retrieval from speckle-based X-ray imaging (SBXI) data. MIST is based on the X-ray Fokker-Planck equation, requiring the inversion of derivative operators that are often numerically unstable. These instabilities can be addressed by employing regularization techniques, such as Tikhonov regularization. The regularization output is highly sensitive to the choice of the Tikhonov regularization parameter, making it crucial to select this value carefully and optimally. Here, we present an automated iterative algorithm to optimize the regularization of the inverse Laplacian operator in our most recently published MIST variant, addressing the operator's instability near the Fourier-space origin. Our algorithm leverages the inherent stability of the phase solution obtained from the transport-of-intensity equation for SBXI, using it as a reliable ground truth for the more complex Fokker-Planck-based algorithms that incorporate the dark-field signal. We applied the algorithm to an SBXI dataset collected using synchrotron light of a four-rod sample. The four-rod sample's phase and dark-field images were optimally retrieved using our developed algorithm, eliminating the tedious and subjective task of selecting a suitable Tikhonov regularization parameter. The developed regularization-optimization algorithm makes MIST more user-friendly by eliminating the need for manual parameter selection. We anticipate that our optimization algorithm can also be applied to other image retrieval approaches derived from the Fokker-Planck equation.

X射线成像图像重建正则化优化暗场成像

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