Browsing by Author "Evans, J. Paul O."
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Item Open Access Classification of fracture and non-fracture groups by analysis of coherent X-ray scatter(Nature Publishing Group, 2016-07-01) Dicken, A. J.; Evans, J. Paul O.; Rogers, Keith; Stone, N.; Greenwood, Charlene; Godber, S. X.; Clement, J. G.; Lyburn, Iain Douglas; Martin, R. M.; Zioupos, PeterOsteoporotic fractures present a significant social and economic burden, which is set to rise commensurately with the aging population. Greater understanding of the physicochemical differences between osteoporotic and normal conditions will facilitate the development of diagnostic technologies with increased performance and treatments with increased efficacy. Using coherent X-ray scattering we have evaluated a population of 108 ex vivo human bone samples comprised of non-fracture and fracture groups. Principal component fed linear discriminant analysis was used to develop a classification model to discern each condition resulting in a sensitivity and specificity of 93% and 91%, respectively. Evaluating the coherent X-ray scatter differences from each condition supports the hypothesis that a causal physicochemical change has occurred in the fracture group. This work is a critical step along the path towards developing an in vivo diagnostic tool for fracture risk prediction.Item Open Access Confocal energy-dispersive X-ray diffraction tomography employing a conical shell beam(Optical Society of America, 2019-07-01) Dicken, Anthony; Evans, J. Paul O.; Rogers, Keith; Prokopiou, Danae; Godber, Simon; Elarnaut, F.; Shevchuk, Alex; Downes, D.; Wilson, M.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 controlItem Open Access Depth resolved snapshot energy-dispersive X-ray diffraction using a conical shell beam(Optical Society of America, 2017-08-23) Dicken, A. J.; Evans, J. Paul O.; Rogers, Keith; Prokopiou, Danae; Godber, S. X.; Wilson, M.We demonstrate a novel imaging architecture to collect range encoded diffraction patterns from overlapping samples in a single conical shell projection. The patterns were measured in the dark area encompassed by the beam via a centrally positioned aperture optically coupled to a pixelated energy-resolving detector. We show that a single exposure measurement of 0.3 mAs enables d-spacing values to be calculated. The axial positions of the samples were not required and the resultant measurements were robust in the presence of crystallographic textures. Our results demonstrate rapid volumetric materials characterization and the potential for a direct imaging method, which is of great relevance to applications in medicine, non-destructive testing and security screening.Item Open Access Fracture toughness of the cancellous bone of FNF femoral heads in relation to its microarchitecture(European Society of Biomechanics, 2016-07) Greenwood, Charlene; Clements, J. G.; Dicken, A. J.; Evans, J. Paul O.; Lyburn, Iain Douglas; Martin, R. M.; Rogers, Keith; Stone, N.; Adams, G.; Zioupos, PeterThis study considers the relationship between microarchitecture and mechanical properties for cancellous bone specimens collected from a cohort of patients who had suffered fractured necks of femur. OP is an acute skeletal condition with huge socioeconomic impact [1] and it is associated with changes in both bone quantity and quality [2], which affect greatly the strength and toughness of the tissue [3].Item Open Access Investigating pair distribution function use in analysis of nanocrystalline hydroxyapatite and carbonate-substituted hydroxyapatite(International Union of Crystallography, 2022-04-14) Arnold, Emily; Keeble, Dean S.; Evans, J. Paul O.; Greenwood, Charlene; Rogers, Keith D.Hydroxyapatite (HA) is a complex material, which is often nanocrystalline when found within a biological setting. This work has directly compared the structural characteristics derived from data collected using a conventional laboratory-based X-ray diffractometer with those collected from a dedicated pair distribution function (PDF) beamline at Diamond Light Source. In particular, the application of PDF analysis methods to carbonated HA is evaluated. 20 synthetic samples were measured using both X-ray diffraction (XRD) and PDFs. Both Rietveld refinement (of laboratory XRD data) and real-space refinement (of PDF data) were used to analyse all samples. The results of Rietveld and real-space refinements were compared to evaluate their application to crystalline and nanocrystalline hydroxyapatite. Significant relationships were observed between real-space refinement parameters and increasing carbonate substitution. Understanding the local order of synthetic hydroxyapatite can benefit several fields, including both biomedical and clinical settings.Item Open Access Sparse interleaved sampling for high resolution focal construct geometry X-ray tomography(Optical Society of America, 2023-04-24) Evans, J. Paul O.; Elarnaut, F.; Downes, D.; Lee, W. K.; Arnold, Emily; Rogers, KeithWe 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.