Conical shell illumination incorporating a moving aperture for depth-resolved high-energy X-ray diffraction.

In many applications, the main limitation of X-ray absorption methods is that the signals measured are a function of the attenuation coefficient, which tells us almost nothing about the chemical or crystallographic nature of objects under inspection. To calculate fundamental crystallographic parameters requires the measurement of diffracted photons from a sample. Standard laboratory diffraction methods have been refined for well over a century and provide 'gold standard' structural models for well-prepared samples and single crystals but have little applicability for thick heterogeneous samples as demanded by many screening applications. We present a new high-energy X-ray diffraction probe, which in comparison with previous depth-resolving hollow beam techniques, requires a single beam, point detector and a simple swept aperture to resolve sample signatures at unknown locations within an inspection space. We perform Monte Carlo simulations to support experiments on both single- and multiple-material localisation and identification. The new probe is configured and tested using low-cost commercial components to provide a rapid and cost-effective solution for applications including explosives detection, process control and diagnostics.

A new parafocusing paradigm for X-ray diffraction.

A new approach to parafocusing X-ray diffraction implemented with an annular incident beam is demonstrated for the first time. The method exploits an elliptical specimen path on a flat sample to produce relatively high intensity maxima that can be measured with a point detector. It is shown that the flat-specimen approximation tolerated by conventional Bragg-Brentano geometries is not required. A theoretical framework, simulations and experimental results for both angular- and energy-dispersive measurement modes are presented and the scattering signatures compared with data obtained with a conventional pencil-beam arrangement.

Age-Related Changes in Femoral Head Trabecular Microarchitecture.

Osteoporosis is a prevalent bone condition, characterised by low bone mineral density and increased fracture risk. Currently, the gold standard for identifying osteoporosis and increased fracture risk is through quantification of bone mineral density using dual energy X-ray absorption. However, many studies have shown that bone strength, and consequently the probability of fracture, is a combination of both bone mass and bone 'quality' (architecture and material chemistry). Although the microarchitecture of both non-fracture and osteoporotic bone has been previously investigated, many of the osteoporotic studies are constrained by factors such as limited sample number, use of ovariectomised animal models, and lack of male and female discrimination. This study reports significant differences in bone quality with respect to the microarchitecture between fractured and non-fractured human femur specimens. Micro-computed tomography was utilised to investigate the microarchitecture of femoral head trabecular bone from a relatively large cohort of non-fracture and fracture human donors. Various microarchitectural parameters have been determined for both groups, providing an understanding of the differences between fracture and non -fracture material. The microarchitecture of non-fracture and fracture bone tissue is shown to be significantly different for many parameters. Differences between sexes also exist, suggesting differences in remodelling between males and females in the fracture group. The results from this study will, in the future, be applied to develop a fracture model which encompasses bone density, architecture and material chemical properties for both female and male tissues.

Dual conical shell illumination for volumetric high-energy X-ray diffraction imaging.

To retrieve crystallographic information from extended sample volumes requires a high-energy probe. The use of X-rays to combine imaging with materials characterisation is well-established. However, if fundamental crystallographic parameters are required, then the collection and analysis of X-rays diffracted by the inspected samples are prerequisites. We present a new X-ray diffraction imaging architecture, which in comparison with previous depth-resolving hollow beam techniques requires significantly less X-ray power or alternatively supports significantly increased scanning speeds. Our conceptual configuration employs a pair of conical shell X-ray beams derived from a single point source to illuminate extended samples. Diffracted flux measurements would then be obtained using a pair of energy resolving point detectors. This dual beam configuration is tested using a single X-ray beam set-up employing a dual scan. The use of commercial off-the-shelf low-cost components has the potential to provide rapid and cost-effective performance in areas including industrial process control, medical imaging and explosives detection.

High energy transmission annular beam X-ray diffraction.

We demonstrate material phase retrieval by linearly translating extended polycrystalline samples along the symmetry axis of an annular beam of high-energy X-rays. A series of pseudo-monochromatic diffraction images are recorded from the dark region encompassed by the beam. We measure Bragg maxima from different annular gauge volumes in the form of bright spots in the X-ray diffraction intensity. We present the experiment data from three materials with different crystallographic structural properties i.e. near ideal, large grain size and preferred orientation. This technique shows great promise for analytical inspection tasks requiring highly penetrating radiation such as security screening, medicine and non-destructive testing.

A potential new diagnostic tool to aid DNA analysis from heat compromised bone using colorimetry: A preliminary study.

Extracting viable DNA from many forensic sample types can be very challenging, as environmental conditions may be far from optimal with regard to DNA preservation. Consequently, skeletal tissue can often be an invaluable source of DNA. The bone matrix provides a hardened material that encapsulates DNA, acting as a barrier to environmental insults that would otherwise be detrimental to its integrity. However, like all forensic samples, DNA in bone can still become degraded in extreme conditions, such as intense heat. Extracting DNA from bone can be laborious and time-consuming. Thus, a lot of time and money can be wasted processing samples that do not ultimately yield viable DNA. We describe the use of colorimetry as a novel diagnostic tool that can assist DNA analysis from heat-treated bone. This study focuses on characterizing changes in the material and physical properties of heated bone, and their correlation with digitally measured color variation. The results demonstrate that the color of bone, which serves as an indicator of the chemical processes that have occurred, can be correlated with the success or failure of subsequent DNA amplification.

Validation study of a ray-tracing simulator for focal construct geometry.

We present the results of a computer modelling package designed to simulate X-ray diffraction imaging employing focal construct geometry. The paths of coherently diffracted X-rays are modelled by ray-tracing. The results of the study show good agreement between simulated and measured data obtained in the laboratory. The validation of the modelling package permits the rapid optimisation and prototyping of focal construct technology, which has wide applicability in security X-ray imaging.

X-ray diffraction tomography employing an annular beam.

We demonstrate depth-resolved materials characterization by scanning a sample through an annular beam of X-rays. We measure Bragg X-ray diffraction from a sample with a planar detector positioned centrally in a circular dark field defined by the annular beam. The diffraction maxima are optically encoded with the position of crystalline phases along this beam. Depth-resolved material phase images are recovered via tomosynthesis. We demonstrate our technique using a heterogeneous three-dimensional object comprising three different phases; cyclotetramethylene - tetranitramine, copper and nickel, distributed in a low density medium. Our technique has wide applicability in analytical imaging and is scalable with respect to both scan size and X-ray energy.

Discrimination of liquids by a focal construct X-ray diffraction geometry.

A novel technique for the discrimination of liquids based upon X-ray diffraction and focal construct technology (FCT) is presented. FCT is a new, high efficiency coherent scatter harvesting technique. In this work, the competence of FCT to discriminate liquids was explored. A variety of liquids relevant to security inspection was analysed by FCT for application to liquid security inspection. Discrimination of potential threat liquids was successfully and reliably achieved even for limited data sets.

Combined X-ray diffraction and kinetic depth effect imaging.

In this preliminary study we present a depth resolved transmission image sequence of an object combined with the materials discriminating ability of angular dispersive X-ray diffraction. Volumes within the object giving rise to diffraction patterns matched to a library of specific materials have been encoded visually within the images. The intensity of these highlighted areas has been weighted based on the certainty of the match. Both the theory and experimental proof of principle have been demonstrated. Considerations pertaining to a "scaled up" version of this technique are also discussed.

Position determination of scatter signatures--a novel sensor geometry.

A novel diffraction sensor geometry able to provide the diffraction pattern of a suspect material without prior knowledge of the samples location is introduced. The sensor geometry can also resolve diffraction patterns originating from multiple unknown materials overlapped along the primary X-ray beam path. This is achieved through tracking Bragg peak maxima that linearly propagate from the inspection volume at a series of X-ray detector positions. A series of simulations and experiments have been performed to verify this technique and provide an insight into its characteristics. Such a technique could have widespread appeal in the security industry. Areas of most relevance include the materials characterisation of volumes such as those prevalent in an airport screening environment or equally the rapid screening for illicit drugs trafficked through the postal system.

The separation of X-ray diffraction patterns for threat detection.

We introduce a novel method for identifying materials using a series of X-ray diffractograms collected in transmission. A multiple perspective approach is used to identify the diffractograms produced by materials located at different positions along the primary X-ray beam. This technique promises to enhance materials identification performance in cluttered environments such as those prevalent in aviation security screening.