多模态本征散斑跟踪（MIST）用于提取快速变化的漫散射X射线散射
Multimodal Intrinsic Speckle-Tracking (MIST) to extract rapidly-varying diffuse X-ray scatter
AI总结：
本文扩展了多模态本征散斑跟踪（MIST）形式体系，消除了漫射暗场信号须空间缓慢变化的限制，从而能更准确地提取快速变化的X射线散射信号，提升了图像质量并促进了多领域应用。
摘要：
基于散斑的相位对比X射线成像（SB-PCXI）能够重建弱衰减材料的高分辨率图像，这些材料在传统的基于衰减的成像中通常是难以区分的。SB-PCXI的实验装置仅需一个足够相干的光源和一个空间随机掩模，该掩模放置在光源和探测器之间。该技术能够提取小于成像系统空间分辨率的长度尺度上的样品信息；这实现了多模态信号重建。“多模态本征散斑跟踪”（MIST）是一种从Fokker-Planck方程的近轴光学形式推导出的快速确定性形式体系。MIST同时从样品中提取衰减、折射和小角散射（漫射暗场）信号，并且与替代的散斑跟踪方法相比具有更高的计算效率。迄今为止，MIST的变体假设漫射暗场信号在空间上缓慢变化。尽管取得成功，但这些方法无法很好地描述未分辨的样品微观结构，其统计形式在空间上并非缓慢变化。在此，我们扩展了MIST形式体系，使得对于样品的旋转各向同性漫射暗场信号不再有这种限制。我们重建了两个样品的多模态信号，每个样品具有不同的X射线衰减和散射特性。与假设漫射暗场是横向位置缓慢变化函数的先前方法相比，重建的漫射暗场信号具有更优的图像质量。我们的推广可能有助于促进SB-PCXI在工程、生物医学、林业和古生物学等领域的更广泛应用，并有望推动基于散斑的漫射暗场张量断层扫描的发展。
英文摘要：
Speckle-based phase-contrast X-ray imaging (SB-PCXI) can reconstruct high-resolution images of weakly-attenuating materials that would otherwise be indistinguishable in conventional attenuation-based imaging. The experimental setup of SB-PCXI requires only a sufficiently coherent source and spatially random mask, positioned between the source and detector. The technique can extract sample information at length scales smaller than the imaging system's spatial resolution; this enables multimodal signal reconstruction. ``Multimodal Intrinsic Speckle-Tracking'' (MIST) is a rapid and deterministic formalism derived from the paraxial-optics form of the Fokker-Planck equation. MIST simultaneously extracts attenuation, refraction, and small-angle scattering (diffusive-dark-field) signals from a sample and is more computationally efficient compared to alternative speckle-tracking approaches. Hitherto, variants of MIST have assumed the diffusive-dark-field signal to be spatially slowly varying. Although successful, these approaches have been unable to well-describe unresolved sample microstructure whose statistical form is not spatially slowly varying. Here, we extend the MIST formalism such that there is no such restriction, in terms of a sample's rotationally-isotropic diffusive-dark-field signal. We reconstruct multimodal signals of two samples, each with distinct X-ray attenuation and scattering properties. The reconstructed diffusive-dark-field signals have superior image quality compared to our previous approaches which assume the diffusive-dark-field to be a slowly varying function of transverse position. Our generalisation may assist increased adoption of SB-PCXI in applications such as engineering and biomedical disciplines, forestry, and palaeontology, and is anticipated to aid the development of speckle-based diffusive-dark-field tensor tomography.
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