Crystalline phase discriminating neutron tomography using advanced reconstruction methods
Crystalline phase discriminating neutron tomography using advanced reconstruction methods
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DOI：
10.1088/1361-6463/ac02f9
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发表时间：
2021-08-12
影响因子：
3.4
通讯作者：
Withers, Philip J.
中科院分区：
文献类型：
--
作者：
Ametova, Evelina;Burca, Genoveva;Withers, Philip J.
飞行时间（ToF）中子成像与X射线计算机断层扫描形成互补的衰减对比，并且能够从图像中每个点（体素）的作为中子能量（ToF）函数的衰减变化中提取额外信息。特别是，布拉格边缘位置提供了晶体学信息，因此能够直接识别晶相。在此，我们展示了具有高空间和光谱分辨率的布拉格边缘断层扫描。我们提出了一种新的迭代断层重建方法，该方法具有定制的正则化项，以便从低计数数据中实现高质量重建，而传统的滤波反投影（FBP）在这种情况下会失败。正则化在空间和光谱维度上以分离的模式起作用，并有利于在相应维度上呈现特征性的分段常数和分段平滑行为。我们将所提出的方法与FBP以及一种用于多材料体模的多通道断层扫描的先进正则化方法进行了比较。所提出的适应特定图像特性的新正则化方法优于传统方法和先进方法，因此有利于在体素层面进行布拉格边缘拟合。所提出的方法需要显著更短的曝光时间来获取感兴趣的特征。这反过来又有利于更高效地利用昂贵的中子束线时间，并能够充分利用先进的高分辨率探测器。
Time-of-flight (ToF) neutron imaging offers complementary attenuation contrast to x-ray computed tomography, coupled with the ability to extract additional information from the variation in attenuation as a function of neutron energy (ToF) at every point (voxel) in the image. In particular, Bragg edge positions provide crystallographic information and therefore enable the identification of crystalline phases directly. Here we demonstrate Bragg edge tomography with high spatial and spectral resolution. We propose a new iterative tomographic reconstruction method with a tailored regularisation term to achieve high quality reconstruction from low-count data, where conventional filtered back-projection (FBP) fails. The regularisation acts in a separated mode for spatial and spectral dimensions and favours characteristic piece-wise constant and piece-wise smooth behaviour in the respective dimensions. The proposed method is compared against FBP and a state-of-the-art regulariser for multi-channel tomography on a multi-material phantom. The proposed new regulariser which accommodates specific image properties outperforms both conventional and state-of-the-art methods and therefore facilitates Bragg edge fitting at the voxel level. The proposed method requires significantly shorter exposures to retrieve features of interest. This in turn facilitates more efficient usage of expensive neutron beamline time and enables the full utilisation of state-of-the-art high resolution detectors.