X-ray diffraction tomography with limited projection information

Abstract

X-ray diffraction tomography (XDT) records the spatially-resolved X-ray diffraction profile of an extended object. Compared to conventional transmission-based tomography, XDT displays high intrinsic contrast among materials of similar electron density and improves the accuracy in material identification thanks to the molecular structural information carried by diffracted photons. However, due to the weak diffraction signal, a tomographic scan covering the entire object typically requires a synchrotron facility to make the acquisition time more manageable. Imaging applications in medical and industrial settings usually do not require the examination of the entire object. Therefore, a diffraction tomography modality covering only the region of interest (ROI) and subsequent image reconstruction techniques with truncated projections are highly desirable. Here we propose a table-top diffraction tomography system that can resolve the spatially-variant diffraction form factor from internal regions within extended samples. We demonstrate that the interior reconstruction maintains the material contrast while reducing the imaging time by 6 folds. The presented method could accelerate the acquisition of XDT and be applied in portable imaging applications with a reduced radiation dose.

Interior x-ray diffraction tomography with low-resolution exterior information

“…Among all the sampling points in ROI region, 16%, 3.5%, 0.8%, and 2.6% are misclassified in (b1-b4), respectively, which clearly indicates that a wrong sinogram extrapolation leads to higher classification error. The material maps of correct sinogram extrapolation, IR-TV and LR exterior scan (b2-b4) have similar performance, which agrees with the previously reported results [18] that IR-TV can achieve comparable material specificity as a full-scan XDT. In Figure 5 and Figure 6, a correctly extrapolated sinogram and our proposed LR exterior scan display similar reconstruction results and material specificity.…”

“…In medical diagnosis or industrial inspection, XDT is ideal for a secondary scan, in which only the material composition within an ROI is desired [16,17]. For these applications, interior XDT limits the projection measurement to the ROI region to reduce the imaging time and excessive radiation dose outside ROI, and provides comparable material specificity as a full XDT scan [18]. Similar to the interior problem in CT, interior XDT also requires prior knowledge about the object, either in the form of a known sub-region [19,20] or piecewise constant constraint [21,22], to stabilize the ROI reconstruction.…”

Few-photon computed x-ray imaging

“…The reduced dose opens up new opportunities in dose-sensitive biomedical or industrial non-invasive inspection applications. In addition to the presented projection and CT modalities, the photon-counting scheme can also be applied to reduce the imaging time of X-ray diffraction tomography [18], where the diffraction signal is intrinsically ~3 orders of magnitude weaker than the transmitted signal [19]. We could further exploit the energy sensitivity of X-ray photoncounting detectors to perform energy-dispersive CT or diffraction tomography for threedimensional, in situ material identification.…”

Benign Hydrothermal Synthesis of N‐doped TiO2 and TiO2‐CoS Nanostructures for Enhanced Visible‐Light Driven Photocatalytic Activity

“…[6,12,14,22,26] Besides doping and coupling with other suitable semiconductors, other strategies such as, dimensional consideration with increased specific surface area, preparation of high reactive facet-dominated single nano-crystal, and formation of core-shell heterostructures exploiting the plasmonic enhancement effect have been adopted by the researchers to improve the photocatalytic activity of pure TiO 2 . [42][43][44][45][46][47][48] This present work aims at the preparation of N-doped TiO 2 -CoS nanocomposite-for the first-time-towards environmental remediation with highlighting of preliminary results. In this article, we attempted a cocktail approach to fabricate N-doped fibrous TiO 2 -CoS nanocomposite combining three widely utilized strategies such as, doping (with N element), dimensional factor (1D TiO 2 nanofiber) and compositing with relatively narrower band gap semiconductor (coupling with CoS (1.13-1.7 eV)) to effectively enhance photocatalytic performance of the final composite product.…”