Gratings-based phase contrast x-ray imaging offers enhanced material information in an x-ray imaging measurement, a key consideration for improving performance in explosives detection. Application of phase contrast imaging to explosives detection requires addressing several key technical issues: identifying a patterning element (grating) that offers an appropriate tradeoff between sensitivity and robust operation at high energies, developing techniques that allow for quantitative interpretation of new signatures under a broad range of attenuation conditions, and designing a system that allows for rapid measurement while providing sufficient signal-to-noise. We present results illustrating the value of phase contrast x-ray signatures for explosives detection, and demonstrate the ability to obtain quantitative metrics in the presence of intervening materials. Finally, we demonstrate preliminary results from a gratings-based phase contrast system in a scanning configuration.
Gratings-based phase contrast X-ray imaging provides additional materials signatures in textured media based on the deflection of the X-ray beam. Using this technique with a hard (~160 kVp) X-ray spectrum has shown potential for improved materials discrimination in applications such as explosives detection. Typical phase contrast measurements rely on relatively broad bremsstrahlung spectra, resulting in measurement responses averaged across wide energy ranges. Here, we present results for gratings-based phase contrast measurements using a spectroscopic imaging detector. This allows for direct observation of phase-contrast material cross sections as a function of energy, without the need for a mono-energetic X-ray source. Further, the measurements provide a direct understanding of spectral variations and a technical basis for application of hard X-ray gratings-based phase contrast measurements in the presence of attenuating materials.
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