An experimental approach to optimising refraction sensitivity for lab-based edge illumination phase contrast set-ups
An experimental approach to optimising refraction sensitivity for lab-based edge illumination phase contrast set-ups
复制标题
DOI：
10.1088/1361-6463/ab747c
复制
发表时间：
2020-05-06
影响因子：
3.4
通讯作者：
Olivo, A.
中科院分区：
文献类型：
--
作者：
Kallon, G. K.;Vittoria, F. A.;Olivo, A.
通过修改设置，可以优化差分X射线相位对比度(XPC)成像方法的折射灵敏度。通常，修改涉及改变源/探测器参数、传播距离或光学部件的设计，即，如果没有大量的时间投入，则不容易改变的参数、更换部件或执行高精度重新校准。边缘照明(EI)xPC方法提供了一种通过利用其周期性掩模的微米平移来优化折射灵敏度的方法，该方法绕过了上面列出的限制。这些平移可以在运行时执行，并允许针对特定应用优化折射信号，而无需对设置进行重大更改。事实证明，该方法对于使用更大信号源但可用安装空间有限的基于实验室的系统是有利的。在这篇文章中，我们研究了在两种常见的实验条件下：(1)在近似恒定的探测计数下，和(2)在相同的曝光时间下，折射敏感度随照明像素分数(IPF)的变化。我们比较了不同IPF下重建折射图像的背景标准差，发现在两种情况下，25%IPF的折射灵敏度都是最优的。最后，我们证明了折射敏感度影响昆虫腿上弱折射特征的可见性。结果表明，当系统参数确定后，尤其是在统计参数保持不变的情况下，采用低于50%的IPF可能更好，并提供了实验验证，即一旦定义了系统参数，EI中的相位灵敏度就不再是固定的。
Refraction sensitivity can be optimised for differential x-ray phase contrast (XPC) imaging methods by modifying the set-up. Often, modifications involve changing source/detector parameters, propagation distances, or the design of optical components, i.e. parameters that are not readily changed without non-trivial time investment, replacing components, or performing high-precision recalibrations. The edge illumination (EI) XPC method provides a method of optimising the refraction sensitivity, by exploiting micrometric translations of its periodic masks, that bypasses the constraints listed above. These translations can be performed on-the-fly and allow optimising the refraction signal for specific applications without making significant changes to the set-up. The method can prove advantageous for lab-based systems that make use of larger sources but with limited available set-up space. In this paper, we study how refraction sensitivity varies as a function of illuminated pixel fraction (IPF) under two commonly encountered experimental conditions: (1) at approximately constant detected counts, and (2) at equal exposure time. We compare the standard deviation in the background of reconstructed refraction images at different IPFs and find that refraction sensitivity is optimal at 25% IPF under both conditions. Finally, we demonstrate that refraction sensitivity affects the visibility of weakly refracting features on an insect leg. The results suggest that IPFs lower than 50% can actually be preferable, especially in the case where the statistics is kept constant, and provide experimental validation that phase sensitivity in EI is not fixed once the system parameters are defined.