Phase Contrast X-Ray Imaging Signatures for Security Applications

Differential phase contrast imaging with a grating interferometer is a promising new radiographic technique providing three distinct contrast mechanisms-absorption, phase, and scatter (or dark field)-using a conventional X-ray tube source. We examine the signatures available in these three contrast mechanisms with attention towards potential security applications. We find that the scatter mode is uniquely sensitive to textured materials, potentially leading to enhanced material discrimination through the use of multiple contrast modes. We find that scatter signal in our imaging system increases as texture size is reduced from 800 μm to 7 μm. This range spans the transition from features that are resolved in the image to those residing below the system resolution, and corresponds to length scales of known texture or density variations in several common explosives.