X-ray diffraction tomography (XDT) resolves the spatially-variant XRD profiles within the object, and provides improved material contrast compared to the conventional transmission-based computed tomography (CT). Due to the small diffraction cross-section, a typical full field-of-view XDT scan takes tens of hours using a table-top X-ray tube. In medical and industrial imaging applications, oftentimes only the XRD measurement within a region-of-interest (ROI) is required, which, together with the demand to reduce imaging time and radiation dose to the sample, motivates the development of interior XDT systems that scan and reconstruct only an internal region within the sample. However, existing interior reconstruction frameworks rely on a known region or piecewise constant constraint within the ROI, which do not apply to all the samples in XDT. In this presentation, we propose a quasi-interior XDT scheme that incorporates a small fraction of projection information from the exterior region to assist interior reconstruction. The low-resolution exterior projection data obviates the requirement for prior knowledge on the object, and allows the ROI reconstruction to be performed with the fast, widely-used filtered back-projection algorithm for easy integration into real-time XDT imaging modules. We also demonstrate the material classification based on the XDT profile reconstructed from pure interior and our combined ROI and exterior measurements.
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