Croughan Michelle K, Paganin David M, Alloo Samantha J, Ahlers Jannis N, How Ying Ying, Harker Stephanie A, Morgan Kaye S
Monash University, School of Physics and Astronomy, Melbourne, 3800, Australia.
University of Canterbury, School of Physical and Chemical Sciences, Christchurch, 8041, New Zealand.
Sci Rep. 2024 Aug 1;14(1):17807. doi: 10.1038/s41598-024-68659-2.
In recent years, a novel x-ray imaging modality has emerged that reveals unresolved sample microstructure via a "dark-field image", which provides complementary information to conventional "bright-field" images, such as attenuation and phase-contrast modalities. This x-ray dark-field signal is produced by unresolved microstructures scattering the x-ray beam resulting in localised image blur. Dark-field retrieval techniques extract this blur to reconstruct a dark-field image. Unfortunately, the presence of non-dark-field blur such as source-size blur or the detector point-spread-function can affect the dark-field retrieval as they also blur the experimental image. In addition, dark-field images can be degraded by the artefacts induced by large intensity gradients from attenuation and propagation-based phase contrast, particularly around sample edges. By measuring any non-dark-field blurring across the image plane and removing it from experimental images, as well as removing attenuation and propagation-based phase contrast, we show that a directional dark-field image can be retrieved with fewer artefacts and more consistent quantitative measures. We present the details of these corrections and provide "before and after" directional dark-field images of samples imaged at a synchrotron source. This paper utilises single-grid directional dark-field imaging, but these corrections have the potential to be broadly applied to other x-ray imaging techniques.
近年来，一种新型的X射线成像方式出现了，它通过“暗场图像”揭示未解析的样品微观结构，该图像为传统的“明场”图像（如衰减和相衬成像方式）提供了补充信息。这种X射线暗场信号是由未解析的微观结构散射X射线束产生的，导致局部图像模糊。暗场检索技术提取这种模糊来重建暗场图像。不幸的是，诸如源尺寸模糊或探测器点扩散函数等非暗场模糊的存在会影响暗场检索，因为它们也会使实验图像模糊。此外，暗场图像会因衰减和基于传播的相衬产生的大强度梯度所引起的伪影而退化，特别是在样品边缘周围。通过测量图像平面上的任何非暗场模糊并从实验图像中去除它，以及去除基于衰减和传播的相衬，我们表明可以检索到具有更少伪影和更一致定量测量的定向暗场图像。我们展示了这些校正的细节，并提供了在同步辐射源成像的样品的“校正前”和“校正后”定向暗场图像。本文采用单网格定向暗场成像，但这些校正有可能广泛应用于其他X射线成像技术。
