1,721,081 research outputs found
Hybrid Imaging Detectors in X-Ray Phase-Contrast Applications
No full textX-Ray Phase-Contrast Imaging (XPCI) techniques are gaining increasing interest not only within the synchrotron radiation community, where most of them were first developed and implemented, but also among X-ray imaging experts who make use of standard laboratory sources. While conventional X-ray imaging typically depicts the attenuation of an investigated sample, XPCI allows access to complementary information such as refraction and ultra-small-angle-scattering (USAXS). These additional contrast sources lead to a major enhancement in the visibility of structures featuring poor attenuation contrast such as in biological soft tissues and plastic-based samples. Additionally, the USAXS signal reveals inhomogeneities on a scale smaller than the system’s spatial resolution, being suited for the investigation of a wide range of microparticulate samples, spanning, e.g., from lung tissues to composite materials. Independently from XPCI, recent years have witnessed unprecedented development in the field of hybrid X-ray imaging detectors. Novel devices have both led to major advantages over conventional indirect conversion detectors, such as higher efficiency and/or higher spatial resolution, and opened up entirely new possibilities, such as pixel-based energy discrimination of photons, spectral performances, and super-resolution imaging. In this framework, the aim of the chapter is to provide a link between XPCI and novel detector technologies, focusing on the specific role of detectors in the phase signal formation process for the most common XPCI techniques. Adding to the theoretical background, several successful examples of state-of-the-art detectors’ integration with XPCI are provided, as well as a number of foreseeable applications strongly leveraging on novel detectors’ performances
x-Ray Imaging with Coherent Sources
No full text2.08.1 Introduction
2.08.1.1 x-Rays as Waves
2.08.1.2 Coherent x-Ray Sources
2.08.2 Phase-Sensitive Techniques for x-Ray Imaging
2.08.2.1 Propagation-Based Phase-Contrast Imaging
2.08.2.1.1 Methods
2.08.2.1.2 Applications
2.08.2.2 Analyzer-Based Imaging
2.08.2.2.1 Methods
2.08.2.2.2 Applications
2.08.2.3 Coded Apertures Phase Contrast Imaging
2.08.2.3.1 Methods
2.08.2.3.2 Applications
2.08.2.4 Interferometry
2.08.2.4.1 Methods
2.08.2.4.2 Applications
2.08.2.5 Grating Interferometry
2.08.2.5.1 Methods
2.08.2.5.2 Applications
2.08.3 Phase Retrieval and Post-Processing
2.08.4 Open Challenges and Future Perspectives
2.08.4.1 Image Evaluation
2.08.4.2 Contrast Agents for x-Ray Phase-Sensitive Techniques
2.08.4.3 Implementation on Conventional Sources
Reference
Quantitative 3D refractive index decrement reconstruction using single-distance phase-contrast tomography data
No full textX-ray propagation-based phase-contrast imaging is an attractive phase-sensitive imaging technique that has found applications in many research fields. Here, we report the investigations of a method which can quantitatively reconstruct in 3D the refractive index decrement of a quasi-homogeneous object using single-distance phase-contrast tomography data. The method extends the Born-type approximation phase-retrieval algorithm, which is based on the phase-attenuation duality (ε = δ/β, with constant ε) and suitable for homogeneous objects, to tomography and we study its application to quasi-homogeneous objects. The noise performance and the phase-attenuation duality influences of the method are
also investigated. In simulation, the method allows us to quantitatively reconstruct the 3D refractive index decrement for quasi-homogeneous and weakly absorbing samples and it performs well in the practical noise situation. Furthermore, it shows a substantial contrast increase and successfully distinguishes different materials in a quasi-homogeneous and weakly absorbing sample from experimental data, even with inappropriate ε value
Comparison of single distance phase retrieval algorithms by considering different object composition and the effect of statistical and structural noise
No full textPhase retrieval is a technique for extracting quantitative phase information from X-ray propagation-based phase-contrast tomography (PPCT). In this paper, the performance of different single distance phase retrieval algorithms will be investigated. The algorithms are herein called phase-attenuation duality Born Algorithm (PAD-BA), phase-attenuation duality Rytov Algorithm (PAD-RA), phase-attenuation duality Modified Bronnikov Algorithm (PAD-MBA), phase-attenuation duality Paganin algorithm (PAD-PA) and phase-attenuation duality Wu Algorithm (PAD-WA), respectively. They are all based on phase-attenuation duality property and on weak absorption of the sample and they employ only a single distance PPCT data. In this paper, they are investigated via simulated noise-free PPCT data considering the fulfillment of PAD property and weakly absorbing conditions, and with experimental PPCT data of a mixture sample containing absorbing and weakly absorbing materials, and of a polymer sample considering different degrees of statistical and structural noise. The simulation shows all algorithms can quantitatively reconstruct the 3D refractive index of a quasi-homogeneous weakly absorbing object from noise-free PPCT data. When the weakly absorbing condition is violated, the PAD-RA and PAD-PA/WA obtain better result than PAD-BA and PAD-MBA that are shown in both simulation and mixture sample results. When considering the statistical noise, the contrast-to-noise ratio values decreases as the photon number is reduced. The structural noise study shows that the result is progressively corrupted by ring-like artifacts with the increase of structural noise (i.e. phantom thickness). The PAD-RA and PAD-PA/WA gain better density resolution than the PAD-BA and PAD-MBA in both statistical and structural noise study
Generalized diffraction enhanced imaging to retrieve absorption, refraction and scattering effects
No full textMicrobubbles as x-ray scattering contrast agents using analyzer-based imaging
No full textConventional contrast agents utilized in diagnostic radiology are based on x-ray absorption properties; alternative physical principles capable of providing a contrast enhancement in radiographs have never been applied. This study exploits the possibility of using a novel type of contrast media based on x-ray scattering. The contrast agents consist of microbubble echo-enhancing agents, usually applied in ultrasound examinations, which are invisible with conventional x-ray absorption techniques. The experiment was carried out at the medical beamline of the synchrotron radiation laboratory ELETTRA in Trieste, Italy. A flat silicon analyzer crystal typically used for diffraction-enhanced imaging was utilized as a tool for detecting the scattering properties of the contrast agents. In analyzer-based imaging, it is possible to detect the scattering properties of the sample by shifting the analyzer crystal to selected positions of its reflectivity curve. In particular, when the sample consists of a large number of micro-particles an overall effect can be observed. Phantoms containing contrast agents based on microbubbles were imaged at different angular positions of the analyzer crystal. High visibility of the details was demonstrated, and a strong contrast enhancement was measured compared to normal x-ray absorption techniques
Simultaneous determination of the X-ray refractive index and the attenuation length from a single digitally registered radiograph of rectangular prisms
No full textPrisms deflect and disperse X-rays due to refraction very similar to visible light. As X-rays are always attenuated while traversing material, the intensity distribution in the transmitted beam carries information about the prism transmission function. This study will show that sufficient information is contained in a single digitally registered radiograph from a rectangular prism, for deriving both the refractive index of the material and its attenuation length. The measured data can be prepared such that neither intensity fluctuations nor false light content in the incident beam will introduce systematic errors into the result. The strategy is thus very adapted, when single shot pictures are taken at X-ray sources with limited shot reproducibility. This technique is favourably be used at very grazing angles of incidence of the order of the critical angle for the prism material, when the beam deflection becomes significant. In such a geometry dimensional parameters, like sample thickness, do not affect the data analysis, which is particularly insensitive to even significant errors in the tip angle. (C) 2011 Elsevier B.V. All rights reserved
Preliminary results in the use of synchrotron radiation for small cracks and defects investigation in AA FSW samples
No full textA very good definition of defects position and dimension in welded joints is desirable for application of
fracture mechanics techniques and improvement of industrial acceptability criteria. This paper illustrates the
preliminary results obtained in the investigation of defects in aluminum welded joints at SYRMEP beamline of the
Elettra synchrotron radiation facility in Trieste (Italy). The novel PHase Contrast (PHC) imaging technique
consents a definition of the defects better than the one achievable with conventional welded joints control methods
such as ultrasonic techniques, acoustic emission and radiography
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