Besides the well-known conventional X-ray attenuation image, Talbot-Lau X-ray imaging (TLXI) provides additional information about the small-angle scattering and refractive features of an object. In general, TLXI setups have to be mechanically robust, since already slight inaccuracies during the measurement process result in moiré artefacts. This work derives moiré artefacts as a result of phase-stepping inaccuracies. The dependency of these artefacts on the phase-stepping inaccuracies is mathematically derived by a Taylor series expansion and verified by a simulation. Among other things, it is shown that moiré artefacts can be calculated by a weighted mean of phase-stepping position deviations to their target positions. These weighting factors vary for each image. Moiré artefacts can even be affected by object features which are not displayed in the particular contrast. The findings of this work offer the possibility to develop advanced reconstruction algorithms which suppress moiré artefacts in the reconstructed images. This reduces the method’s susceptibility to setup component inaccuracies as well as external influences and hence facilitates TLXI for clinical practice.

中文翻译：

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Talbot-Lau X射线成像中的波纹伪影的分析和模拟研究

除了众所周知的常规X射线衰减图像外，Talbot-Lau X射线成像（TLXI）还提供有关对象的小角度散射和折射特征的其他信息。通常，TLXI设置必须具有机械坚固性，因为在测量过程中本来已经很不精确的结果会导致出现波纹现象。这项工作是由于相位步进误差而产生的莫尔纹伪影。这些伪像对相位步进误差的依赖性是通过泰勒级数展开从数学上得出的，并通过仿真进行了验证。其中显示出，可以通过相位步进位置相对于其目标位置的偏差的加权平均值来计算莫尔伪像。这些权重因数随每个图像而变化。莫尔文物甚至可能会受到对象特征的影响，这些对象特征不会以特定的对比度显示。这项工作的发现为开发先进的重建算法提供了可能，该算法可以抑制重建图像中的波纹伪影。这降低了该方法对组件不准确以及外部影响的敏感性，因此有利于TLXI进行临床实践。