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Experimental (solid line) and calculated (broken line) double-crystal rocking curves of the Si(3 3 3) reflection with MoKa 1 radiation. Background has not been subtracted from the experimental curve. The low-angle, top, and high-angle positions on the rocking curve are indicated by L; T; and H; respectively.
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A two-crystal diffractometer in the non-dispersive configuration is used for measurement of the effects of refraction in weakly absorbing test objects. Characteristic Ka 1 radiation from a fine-focus X-ray tube with Mo anode is used. The probing beam is about 70 mm wide and 3 mm high. The sample is placed between the monochromator and analyzer, and...
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... reflection was used for alignment, and great care was exercised to ensure that the tube focus and the collimating slit were vertical, and that the beam path was in the horizontal plane. The 333 reflection from the monochromator and analyzer was used in the measurements. The two-crystal rocking curve RðeÞ in the non-dispersive setting is shown in Fig. 2 together with the calculated curve; here e is the rocking angle relative to the nominal Bragg angle y B : The width of the rocking curve is very sensitive to the tilt angle of the second crystal. The width was minimized by manual adjustment of the goniometer head, but still the experimental curve is slightly wider due to the vertical ...
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... Here, the real part (d) corresponds to the phase shift owing to scattering, which is expressed as d = 2.70 Â 10 10 (Z/A)rl 2 , where Z/A is the ratio of atomic number-to-mass number, and l is the X-ray wavelength. 37 The imaginary part (b) of the index is related to the linear absorption coefficient m, which is expressed as m = 4pb/l. The optical density D(x,y) and phase-shift F(x,y) are expressed as ...
Nondestructive observations and characterization of low-density materials composed of low-Z elements, such as water or its related substances, are essential for materials and life sciences. However, visualizing these compounds and their phase changes is still challenging. In this study, an approach to X-ray imaging of water-related substances in heavy objects without the use of contrast agents is proposed. The implementation of the approach is based upon X-ray phase shift, in which the optimal photon energy is simulated for high-contrast X-ray imaging. Proof of concept is provided by observations of resins, water, and clathrate hydrates such as CO2 hydrate and tetrahydrofuran (THF) hydrate in an aluminum container by diffraction-enhanced X-ray imaging with synchrotron X-rays of 35 keV. These results suggest that the proposed approach is a unique method for visualizing the transformation of these clathrate hydrates and is also applicable to in situ observations of other objects composed of multiphase materials with small density differences.
... 11 In this method, the phaseshifted X-ray diffracts and generates dark-bright interference fringes at boundaries and interfaces of the sample, resulting in the effect of enhanced edge contrast. 12 For the dimensional metrology of the low Z materials, the X-ray phase contrast images with high resolution and large field of view (FOV) are helpful for the measurement of geometric parameters of the samples. However, due to the inverse relationship between the FOV and the resolution, the image mosaic from a sequence of partial views is needed to reconstruct the panoramic image with large FOV and high resolution simultaneously. ...
Due to the high spatial resolution and contrast, the optical lens coupled X-ray in-line phase contrast imaging system with the secondary optical magnification is more suitable for the characterization of the low Z materials. The influence of the source to object distance and the object to scintillator distance on the image resolution and contrast is studied experimentally. A phase correlation algorithm is used for the image mosaic of a serial of X-ray phase contrast images acquired with high resolution, the resulting resolution is less than 1.0 μm, and the whole field of view is larger than 1.4 mm. Finally, the geometric morphology and the inner structure of various weakly absorbing samples and the evaporation of water in the plastic micro-shell are in situ characterized by the optical lens coupled X-ray in-line phase contrast imaging system.
... The choice of the distance is related to the kind of study of interest. (Image fromKeyriläinen, Fernández, and Suortti 2002). ...
Chronic pain (CP) is a complex sensory disorder characterized by structural changes, i.e. severe anatomical rearrangements of somatosensory cortex, and functional changes, i.e. anomalies in network functional connectivity and in information transmission at the level of thalamo-cortical circuit. From the structural point of view, within each cortical module, a morpho-functional unit can be recognized, also called neuro-glial-vascular unit, where the glial cells represent the bridging structures allowing for the transfer of metabolites and oxygen to neurons. Namely, the functional dependency between neuronal and vascular elements, largely explored by 3D confocal microscopy and two photon microscopy, has expanded the concept of synaptic space to a more complex form, indicated as “tripartite synapse”, where besides the presence of the pre- and post- synaptic neurons, a glial component is added facing on the microvascular context. Due to this dependency it appears, thus, correct to analyse the cortical microscopical effects of the macroscopical picture. Novel studies by our group have recently investigated CP origin and evolution in experimental CP rat models (Seltzer) through microstructural and functional analyses focused both on the cortical neuronal substrate and the blood micromorphological and vasculodynamic properties. The 3D microarchitecture of cortical vascular network has been revealed by means of synchrotron X-ray micro Computed Tomography (CT) at the ID17 and ID16A beamlines (ESRF, Grenoble) and the TOMCAT beamline (SLS, Villigen). A subsequent morphometric analysis of the 3D vascular network has been implemented by means of skeletonization and spatial graph transformation. Then, a comparative study “Neuropathic vs Control”, based on the estimated vascular network properties (number of vessels, branch points, skeleton segments and vessel diameter), showed evident changes in cortical microvascular compartments: a widespread increase of blood microvessels and capillaries in the investigated regions (the somatosensory [SSI] cortical area) has been found in all CP rats. In parallel, a reduced mean value of vessel diameter in all CP rats prove that capillaries and small microvessels are predominantly interested by these angiogenetic events. By investigating the time evolution of the neogenesis, it appears strongly present since the first stage of the neuropathy (2 weeks), fading away, but still present, during the last time stage considered (6 months). In addition, an increased maximum blood flow, sustained by the vascular network, has been found in CP condition, indicating that CP vascular networks are compatible with an enriched blood flow sustained by the promoted novel angiogenesis. These results from micro- and nano-tomography have been further confirmed also by immunofluorescence microscopy analysis: CP samples have shown the positivity to three markers of vascular neo-genesis (VEGFR1, VEGFR2 and VWF). In parallel, to functionally analyse the genesis and the evolution of the thalamo-cortical circuits in CP conditions, the neural activity has been recorded by means of 32-microelectrode matrices implanted in the brain, simultaneously receiving signals from the VPL thalamic nucleus and the SS1 cortex. All the CP groups show connectivity disorders exhibited also by the evolution of the network topology from “Modules and Hubs” to a “random” network organisation where the intra-community and inter-community functional connections decrease. These results clearly confirm how the neuronal dynamics is strictly linked to the vascular activity: the cortical microvessel neo-genetic events in CP are strongly correlated to the functional anomalies in neuronal network dynamic. The microvascular involvement in CP opens a new way of interpretation of CP disease, not only recognized as sensory pathology, but also as a neurological disease where neuronal and vascular connectivity networks are extensively involved in the whole system.
... The effect is to increase the absorption contrast that is seen as demonstrated in figure 2. The term DEI used by Chapman et al (1997) has come to define the simplest form of analysis of the ABI images in which the RC of the analyser is approximated as a triangle-the first-order Taylor expansion. The enhanced refraction contrast in the ABI images, particularly at the edges of objects, was demonstrated to be very large and theoretically predictable (Keyriläinen et al 2002). ...
... The expression diverges when the ray is parallel to the interface so that sharp refraction contrast takes place at an internal or external edge of the object. It has been verified by measurements that (6a) and (6b) holds quantitatively even when the refraction effect is very large (Keyriläinen et al 2002). ...
... In an ideal ABI measurement, the entire analyser RC modified by the beam traversing the object is recorded and compared with the intrinsic RC. The intrinsic RC has typically wider and higher tails than expected from the calculated convolution of the monochromator and analyser RCs (Keyriläinen et al 2002). The extra intensity is due to thermal diffuse scattering that peaks at the Bragg reflections and is not attenuated by total reflection from a thin surface layer. ...
Analyser-based imaging (ABI) is one of the several phase-contrast x-ray imaging techniques being pursued at synchrotron radiation facilities. With advancements in compact source technology, there is a possibility that ABI will become a clinical imaging modality. This paper presents the history of ABI as it has developed from its laboratory source to synchrotron imaging. The fundamental physics of phase-contrast imaging is presented both in a general sense and specifically for ABI. The technology is dependent on the use of perfect crystal monochromator optics. The theory of the x-ray optics is developed and presented in a way that will allow optimization of the imaging for specific biomedical systems. The advancement of analytical algorithms to produce separate images of the sample absorption, refraction angle map and small-angle x-ray scattering is detailed. Several detailed applications to biomedical imaging are presented to illustrate the broad range of systems and body sites studied preclinically to date: breast, cartilage and bone, soft tissue and organs. Ultimately, the application of ABI in clinical imaging will depend partly on the availability of compact sources with sufficient x-ray intensity comparable with that of the current synchrotron environment. (Some figures may appear in colour only in the online journal)
... The two perspectives are equivalent for object spatial scales L, propagation distances q, and light wavelengths λ that correspond to Fresnel numbers F L 2 ∕qλ ≫ 1. This refraction-enhanced imaging regime is of interest in fields such as biological and medical imaging and astronomy456789 and is of greatest interest for ICF research [10]. The transport of intensity equation (TIE)111213 is typically used to interpret the transmitted intensity pattern I
x; y; z along the z axis line of sight: ...
We present a simple solution to the Fresnel–Kirchoff diffraction integral that is appropriate for x-ray radiography of strongly absorbing and phase-shifting objects in the geometrical optics regime, where phase contrast enhancements can be considered to be caused by refraction by a semi-opaque object. We demonstrate its accuracy by comparison to brute-force numerical ray trace and diffraction calculations of a representative simulated object, and show excellent agreement for spatial scales corresponding to Fresnel numbers greater than unity. The result represents a significant improvement over approximate formulas typically used in analysis of refraction-enhanced radiographs, particularly for radiography of transient phenomena in objects that strongly refract and show significant absorption.
... The two perspectives approach equivalence for object spatial scales L, propagation distances q, and light wavelengths λ that correspond to Fresnel numbers F L 2 ∕qλ greater than unity. This refraction-enhanced imaging regime is of interest in fields, such as medical imaging10111213 and astronomy [14] and is generally of greatest interest for inertial confinement fusion (ICF) implosion plasma research [7]. Earlier work [7] began to explore refractionenhanced radiography of implosion plasmas. ...
X-ray backlit radiographs of dense plasma shells can be significantly altered by refraction of x rays that would otherwise travel straight-ray paths, and this effect can be a powerful tool for diagnosing the spatial structure of the plasma being radiographed. We explore the conditions under which refraction effects may be observed, and we use analytical and numerical approaches to quantify these effects for one-dimensional radial opacity and density profiles characteristic of inertial-confinement fusion (ICF) implosions. We also show how analytical and numerical approaches allow approximate radial plasma opacity and density profiles to be inferred from point-projection refraction-enhanced radiography data. This imaging technique can provide unique data on electron density profiles in ICF plasmas that cannot be obtained using other techniques, and the uniform illumination provided by point-like x-ray backlighters eliminates a significant source of uncertainty in inferences of plasma opacity profiles from area-backlit pinhole imaging data when the backlight spatial profile cannot be independently characterized. The technique is particularly suited to in-flight radiography of imploding low-opacity shells surrounding hydrogen ice, because refraction is sensitive to the electron density of the hydrogen plasma even when it is invisible to absorption radiography. It may also provide an alternative approach to timing shockwaves created by the implosion drive, that are currently invisible to absorption radiography.
... The two perspectives approach equivalence for object spatial scales L, propagation distances q, and light wavelengths λ that correspond to Fresnel numbers F L 2 ∕qλ greater than unity. This refraction-enhanced imaging regime is of interest in fields, such as medical imaging10111213 and astronomy [14] and is generally of greatest interest for inertial confinement fusion (ICF) implosion plasma research [7]. Earlier work [7] began to explore refractionenhanced radiography of implosion plasmas. ...
... The expression diverges when the ray is tangent to the interface, and in practice this means sharp refraction contrast at the edge of the object. It has been verified by measurements on cylindrical objects that (4) holds quantitatively (Keyriläinen et al 2002). Despite the origin of refraction being a lateral gradient in the amplitude of forward scattering, the term 'refraction' is reserved for cases where the deviation of the ray is observed at the detector or by an angular analyzer, arising from density variations in length scale of micrometers. ...
Phase-contrast x-ray imaging (PCI) is an innovative method that is sensitive to the refraction of the x-rays in matter. PCI is particularly adapted to visualize weakly absorbing details like those often encountered in biology and medicine. In past years, PCI has become one of the most used imaging methods in laboratory and preclinical studies: its unique characteristics allow high contrast 3D visualization of thick and complex samples even at high spatial resolution. Applications have covered a wide range of pathologies and organs, and are more and more often performed in vivo. Several techniques are now available to exploit and visualize the phase-contrast: propagation- and analyzer-based, crystal and grating interferometry and non-interferometric methods like the coded aperture. In this review, covering the last five years, we will give an overview of the main theoretical and experimental developments and of the important steps performed towards the clinical implementation of PCI.
... It is important to note that the monochromaticity, high intensity, parallel geometry and coherence of the third generation synchrotron X-ray beams are necessary characteristics for both imaging methods. Analyser-based imaging ABI is a new X-ray imaging technique that uses monochromatic radiation to produce a refraction map of the ob- ject [9, 10]. The technique is based on the use of a perfect crystal (silicon) between the sample and the detector (the analyser). ...
During the last 30 years many groups have carried out experiments and trials to develop new imaging and radiotherapy techniques in oncology, based on the use of synchrotron X-rays. There are several synchrotron biomedical stations around the world, which offer an excellent platform to improve either the imaging diagnosis or radiotherapy treatment for different tumour types. In the coming months the first radiotherapy clinical trials will be seen at the Biomedical Beamline at the ESRF synchrotron in Grenoble (France). In this article we highlight the results of some of the techniques and strategies that have been developed at different biomedical synchrotron stations.
... One way to improve the contrast is through the use of x-ray phase-contrast imaging techniques (Snigirev et al 1995, Wilkins et al 1996. Over the last few years, essentially three different techniques have been developed: propagation-based phase-contrast imaging (Mayo et al 2003, Cloetens et al 2006, crystal or grating analyzer-based phase-contrast imaging (Zhong et al 2000, Keyriläinen et al 2002, Bravin 2003, Clauser 1998, David et al 2002. Schematic view of the experimental setup. ...
The basic principles of x-ray image formation in radiology have remained essentially unchanged since Röntgen first discovered x-rays over a hundred years ago. The conventional approach relies on x-ray attenuation as the sole source of contrast and draws exclusively on ray or geometrical optics to describe and interpret image formation. Phase-contrast or coherent scatter imaging techniques, which can be understood using wave optics rather than ray optics, offer ways to augment or complement the conventional approach by incorporating the wave-optical interaction of x-rays with the specimen. With a recently developed approach based on x-ray optical gratings, advanced phase-contrast and dark-field scatter imaging modalities are now in reach for routine medical imaging and non-destructive testing applications. To quantitatively assess the new potential of particularly the grating-based dark-field imaging modality, we here introduce a mathematical formalism together with a material-dependent parameter, the so-called linear diffusion coefficient and show that this description can yield quantitative dark-field computed tomography (QDFCT) images of experimental test phantoms.
