X-rays have been used for an array of sensing, imaging, and detection tasks for well over 100 years. The birth of radiographic imaging followed mere months after Röntgen’s “discovery” of the X-ray in 1895, and X-ray diffraction (XRD) was already in use for aiding in the determination of crystalline structure by 1912. The pioneering work of Max von Laue and the father–son team of W. L. and W. H. Bragg provided both demonstrations and interpretations of the physics behind XRD and have enabled a variety of refinements, generalizations, and simplifications of the method. As a result, XRD is now a quantitative, versatile, and ubiquitous tool that has been used across science and engineering.
The most common X-ray diffraction systems, however, measure only the XRD signal from a single location on the surface of a sample (i.e., they do not perform imaging). Thus, despite the commercial and scientific success of X-ray diffraction in general, its implementation as a non-imaging modality limits its applicability to the analysis of thin samples and/or surfaces only. As a consequence, many industries have historically not been able to use XRD for performing meaningful material characterization; instead, they have had to settle for transmission-based X-ray imaging, which provides the required spatial information but insufficient material specificity. The inadequacy of this approach is particularly apparent in cases in which both the shape and composition of a sample must be analyzed or in which the material of interest is concealed or otherwise obfuscated. Important examples of these scenarios arise in the diagnosis and detection of cancer in medical imaging and the detection of explosives and/or contraband items for security applications.
Various schemes for transforming XRD into an imaging modality have been proposed, dating back to the late 1980s. While these approaches were successful in demonstrating the capacity for realizing spatially resolved XRD analysis, they were prohibitively slow, expensive, and complicated, typically requiring some combination of a synchrotron X-ray source, cryogenically cooled, high-purity Germanium detectors, and minimal computational resources. As a result, X-ray diffraction imaging was regarded as an interesting prospect but went several decades without significant advancement or adoption for commercial application.