Helical 3-D X-ray Dark-field Imaging

X射线相衬系统的暗场信号捕获微观结构的小角度散射。它是使用Talbot-Lau干涉仪、常规X射线源和常规X射线探测器获得的。有趣的是，暗场信号的测量强度取决于微结构的取向。使用来自断层图像重建的算法，可以恢复这些结构取向。成像结构的尺寸可以显著小于所使用的X射线检测器的分辨率。因此，它是可能的，以前所未有的详细程度调查的结构特性-例如-骨骼或软组织。现有的方法用于3-D暗场重建需要在所有三个空间维度的采样。在实际应用中，这个过程是不可行的。该项目的目标是开发一个系统和一种方法，用于基于实际成像轨迹的测量值进行结构取向的3-D重建。 为此，我们建议使用螺旋轨迹，一个概念，已被应用在传统的CT成像取得了巨大的成功。因此，它将是第一次有可能计算暗场体积从一个实际可行的，连续的成像轨迹。该轨迹不需要物体或患者的多次旋转，避免了不必要的长路径长度。该项目将在实验物理和计算机科学部门之间合作进行。该项目由六个部分组成：- A：三维锥束散射投影模型的开发- B：螺旋暗场成像系统重建算法的开发- C：临床应用重建方法的评估和优化- D：实验性螺旋成像系统的设计- E：螺旋成像系统的设置- F：系统性能的评估和优化A至C部分将由计算机科学系执行。部分D至E将由实验物理系进行。

The dark-field signal of an X-ray phase-contrast system captures the small-angle scattering of microscopic structures. It is acquired using Talbot-Lau interferometer, and a conventional X-ray source and a conventional X-ray detector. Interestingly, the measured intensity of the dark-field signal depends on the orientation of the microstructure. Using algorithms from tomographic image reconstruction, it is possible to recover these structure orientations. The size of the imaged structures can be considerably smaller than the resolution of the used X-ray detector. Hence, it is possible to investigate structural properties of - for example - bones or soft tissue at an unprecedented level of detail.Existing methods for 3-D dark-field reconstruction require sampling in all three spatial dimensions. For practical use, this procedure is infeasible.The goal of the proposed project is to develop a system and a method for 3-D reconstruction of structure orientations based on measurements from a practical imaging trajectory. To this end, we propose to use a helical trajectory, a concept that has been applied in conventional CT imaging with tremendous success. As a result, it will be possible for the first time to compute dark-field volumes from a practically feasible, continuous imaging trajectory. The trajectory does not require multiple rotations of the object or the patient and avoids unnecessarily long path lengths.The project will be conducted in cooperation between the experimental physics and the computer science department. The project is composed of six parts:- A: Development of a 3-D cone-beam scattering projection model- B: Development of reconstruction algorithms for a helical dark-field imaging system- C: Evaluation and optimization of the reconstruction methods towards clinical applications- D: Design of an experimental helical imaging system- E: Setup of the helical imaging system- F: Evaluation and optimization of the system performanceParts A to C will be performed by the computer science department. Parts D to E will be conducted by the experimental physics department.