An X-ray Talbot-Lau grating interferometer enables imaging of X-ray phase contrast. It can measure material transitions that are difficult to observe with traditional attenuation X-ray, for example soft-tissue variations in medical diagnosis or weakly absorbing materials in optical inspection. Unfortunately, the field of view of a Talbot-Lau interferometer is limited to few centimeters due to manufacturing constraints of its gratings. For larger objects, this leads to truncation in the projection images. In a tomographic reconstruction, this truncation causes severe artifacts and prevents the reconstruction of quantitatively correct phase coefficients. In this article, we propose a setup and an algorithm that combine in one scan full-field attenuation with small-field phase measurements. This allows to extrapolate the phase measurements across the full field, and thereby to greatly alleviate truncation artifacts in the reconstructed volume. Evaluation on simulated and real data shows that the method can reliably reconstruct refraction index decrements, that it outperforms the state of the art, and that its performance is in many cases robust to deviations from the initial assumptions.

中文翻译：

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X 射线相衬感兴趣区断层扫描的截断校正

X 射线 Talbot-Lau 光栅干涉仪可实现 X 射线相位对比的成像。它可以测量传统衰减 X 射线难以观察到的材料转变，例如医学诊断中的软组织变化或光学检查中的弱吸收材料。不幸的是，由于光栅的制造限制，Talbot-Lau 干涉仪的视场仅限于几厘米。对于较大的物体，这会导致投影图像被截断。在断层扫描重建中，这种截断会导致严重的伪影并阻止定量正确相位系数的重建。在本文中，我们提出了一种将单次扫描全场衰减与小场相位测量相结合的设置和算法。这允许在整个场上外推相位测量，从而大大减轻重建体积中的截断伪影。对模拟和真实数据的评估表明，该方法可以可靠地重建折射率递减，优于现有技术，并且其性能在许多情况下对初始假设的偏差具有鲁棒性。