Abstract:We demonstrate depth-resolved absorption imaging by scanning an object through a conical shell of X-rays. We measure ring shaped projections and apply tomosynthesis to extract optical sections at different axial focal plane positions. Three-dimensional objects have been imaged to validate our theoretical treatment. The novel principle of our method is scalable with respect to both scan size and X-ray energy. A driver for this work is to complement previously reported methods concerning the measurement of diffracted X-rays for structural analysis. The prospect of employing conical shell beams to combine both absorption and diffraction modalities would provide enhanced analytical utility and has many potential applications in security screening, process control and diagnostic imaging.

Abstract:We demonstrate tomography by measuring a sporadic sequence of ring shaped projections collected during a translational scan. We show that projections using 10% sampling may be used to construct optical sections with peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) of the order of 40 dB and 0.9, respectively. This relatively small degradation in image fidelity was achieved for a 90% potential reduction in X-ray dose coupled with a reduction in scan time. Our approach is scalable in both X-ray energy and inspection volume. A driver for our method is to complement previously reported conical shell beam techniques concerning the measurement of diffracted flux for structural analysis. This work is of great relevance to time critical analytical scanning applications in security screening, process control and diagnostic imaging. Withers, and R. J. Cernik, "3D chemical imaging in the laboratory by hyperspectral X-ray computed tomography," Sci. Rep. 5(1), 15979 (2015). 14. S. Singh and M. Singh, "Explosives detection systems (EDS) for aviation security," Signal Proc. 83(1), 31-55 (2003). 15. K. Wells and D. A. Bradley, "A review of X-ray explosives detection techniques for checked baggage," Appl.

We combine diffraction and absorption tomography by raster scanning samples through a hollow cone of pseudo monochromatic X-rays with a mean energy of 58.4 keV. A single image intensifier takes 90x90 (x,y) snapshots during the scan. We demonstrate a proofof-principle of our technique using a heterogeneous three-dimensional (x,y,z) phantom (90x90x170 mm 3 ) comprised of different material phases, i.e., copper and sodium chlorate. Each snapshot enables the simultaneous measurement of absorption contrast and diffracted flux. The axial resolution was ~1 mm along the (x,y) orthogonal scan directions and ~7 mm along the z-axis. The tomosynthesis of diffracted flux measurements enable the calculation of d-spacing values with ~0.1 Å full width at half maximum (FWHM) at ~2 Å. Thus the identified materials may be color-coded in the absorption optical sections. Characterization of specific material phases is of particular interest in security screening for the identification of narcotics and a wide range of homemade explosives concealed within complex "everyday objects." Other potential application areas include process control and biological imaging. IntroductionRadiographic imaging and the structural analysis of materials using X-rays developed disparately soon after the discovery of X-rays in 1895 [1]. The former has evolved from simple planar imaging into sophisticated tomographic methods [2,3], while the latter formed the basis of X-ray crystallography. Each approach demands quite different spatiotemporal collection and sensing requirements [4,5]. In general, incident X-rays composing a spatial image propagate along a linear path from the source to the detector and do not interact with the materials under inspection. However, the spectroscopic analysis of the transmitted X-rays may provide some useful materials discrimination information [6]. Ultimately, such approaches are limited fundamentally and cannot provide structural or 'molecular resolution' analysis. In contrast, determination of the atomic and molecular structure of crystalline/polycrystalline materials requires analysis of coherently scattered or diffracted Xrays from a sample. The relatively low energy of the interrogating radiation used in laboratory X-ray diffraction (XRD) limits penetration into the sample to near the incident surface. Significantly higher X-ray energies are required (i.e. an order of magnitude increase in photon energy over the legacy 8 keV Cu Kα [7]) for transmission mode diffraction for highly absorbing and or extended thickness samples [7][8][9]. Conventional fan beam tomography has provided diffracted flux measurements [5,[9][10][11] to demonstrate spatially-resolved material specific profiles. Novel compressive tomography promises further reductions in scan times and exposure [12][13][14]. The common problem confronting all volumetric XRD scanning/imaging methods is the production and measurement of sufficient diffracted flux or signal photons to provide the desired scan speed at application dependent energies. These consideration...

We demonstrate interleaved sampling by multiplexing conical subshells within the tomosynthesis and raster scanning a phantom through a 150 kV shell X-ray beam. Each view comprises pixels sampled on a regular 1 mm grid, which is then upscaled by padding with null pixels before tomosynthesis. We show that upscaled views comprising 1% sample pixels and 99% null pixels increase the contrast transfer function (CTF) computed from constructed optical sections from approximately 0.6 line pairs/mm to 3 line pairs/mm. The driver of our method is to complement work concerning the application of conical shell beams to the measurement of diffracted photons for materials identification. Our approach is relevant to time-critical, and dose-sensitive analytical scanning applications in security screening, process control and medical imaging.

We introduce a new high-energy X-ray diffraction tomography technique for volumetric materials characterization. In this method, a conical shell beam is raster scanned through the samples. A central aperture optically couples the diffracted flux from the samples onto a pixelated energy-resolving detector. Snapshot measurements taken during the scan enable the construction of depth-resolved dark-field section images. The calculation of dspacing values enables the mapping of material phase in a volumetric image. We demonstrate our technique using five ~15 mm thick, axially separated samples placed within a polymer tray of the type used routinely in airport security stations. Our method has broad analytical utility due to scalability in both scan size and X-ray energy. Additional application areas include medical diagnostics, materials science, and process control.