ESRF, The European Synchrotron, 71 Avenue des Martyrs, 38000, Grenoble, France.
Univ. Grenoble Alpes, Grenoble, France.
Sci Rep. 2020 Feb 14;10(1):2664. doi: 10.1038/s41598-020-57561-2.
Coherent Diffraction Imaging (CDI), a technique where an object is reconstructed from a single (2D or 3D) diffraction pattern, recovers the lost diffraction phases without a priori knowledge of the extent (support) of the object. The uncertainty of the object support can lead to over-fitting and prevents an unambiguous metric evaluation of solutions. We propose to use a 'free' log-likelihood indicator, where a small percentage of points are masked from the reconstruction algorithms, as an unbiased metric to evaluate the validity of computed solutions, independent of the sample studied. We also show how a set of solutions can be analysed through an eigen-decomposition to yield a better estimate of the real object. Example analysis on experimental data is presented both for a test pattern dataset, and the diffraction pattern from a live cyanobacteria cell. The method allows the validation of reconstructions on a wide range of materials (hard condensed or biological), and should be particularly relevant for 4th generation synchrotrons and X-ray free electron lasers, where large, high-throughput datasets require a method for unsupervised data evaluation.
相干衍射成像（CDI）是一种从单个（2D 或 3D）衍射图样重建物体的技术，无需对象的范围（支撑）的先验知识即可恢复丢失的衍射相位。对象支撑的不确定性会导致过度拟合，并阻止对解决方案进行明确的度量评估。我们建议使用“自由”对数似然指标，其中一小部分点从重建算法中被屏蔽，作为一种无偏度量来评估计算解决方案的有效性，而与研究的样本无关。我们还展示了如何通过特征分解分析一组解决方案，以更好地估计真实对象。我们在实验数据上进行了示例分析，包括测试模式数据集和活蓝藻细胞的衍射图案。该方法允许在广泛的材料（硬凝聚或生物）上验证重建，并且对于第四代同步加速器和 X 射线自由电子激光器尤其相关，其中大型、高吞吐量数据集需要一种用于无监督数据评估的方法。
