ABSTRACT
Computed tomography (CT) is the most common volumetric imaging methods for X-ray, where a cross-sectional attenuation map of the object of interest can be reconstructed from a series of projections from different views. X-ray diffraction tomography (XDT) is a technique that combines the X-ray diffraction (XRD) and CT methods, resolving the diffraction signature of a two- or three-dimensional object from a series of multiplexed diffraction projections. Compared to transmitted photons detected by conventional CT scan, diffracted photons exhibit interference effect, and the resulting diffraction pattern reveals rich information about the molecular structure of the material. Due to the material specificity from the XRD signals, XDT is a promising modality for medical diagnosis and security screening applications. The implementations of XDT system can be divided into three main categories: direct tomography, pencil beam angular dispersive XDT, and fan beam angular dispersive XDT. The recent development of energy-discriminative photon-counting detector array opens the opportunities for energy-dispersive XDT, which could improve the detection efficiency and acquisition speed. Also in this chapter, we will describe recent progress of XDT systems that aim to tackle two major challenges in volumetric X-ray diffraction imaging: I) reconstruction of the textured scattering profile when crystalline material is present; II) high radiation dose due to the weak scattering signal.
