X-ray Absorption Contrast Research Articles

X-ray-induced acoustic computed tomography and its applications in biomedicine.

X-ray-induced acoustic computed tomography (XACT) offers a promising approach to biomedical imaging, leveraging X-ray absorption contrast. It overcomes the shortages of traditional X-ray, allowing for more advanced medical imaging. The review focuses on the significance and draws onto the potential applications of XACT to demonstrate it as an innovative imaging technique. This review navigates the expanding landscape of XACT imaging within the biomedical sphere. Integral topics addressed encompass the refinement of imaging systems and the advancement in image reconstruction algorithms. The review particularly emphasizes XACT's significant biomedical applications. Key uses, such as breast imaging, bone density maps for osteoporosis, and X-ray molecular imaging, are highlighted to demonstrate the capability of XACT. A unique niche for XACT imaging is its application in in vivo dosimetry during radiotherapy, which has been validated on patients. Because of its unique property, XACT has great potential in biomedicine and non-destructive testing. We conclude by casting light on potential future avenues in this promising domain.

Endotaxial Intergrowth of Copper Telluride in GeTe-Rich Germanium Antimony Tellurides Leads to High Thermoelectric Performance

In composite materials with nominal compositions Cu2GexSb2Tex+4 (11 ≤ x ≤ 18, i.e., between Cu6.7Ge36.7Sb6.7Te50 and Cu4.5Ge40.9Sb4.5Te50), precipitates consisting of copper tellurides are endotaxially intergrown in a matrix of Cu-doped germanium antimony tellurides. The precipitates as well as the matrix material undergo various phase transitions as shown by temperature-dependent X-ray diffraction and X-ray absorption contrast imaging. Eventually, the precipitates dissolve in the matrix at temperatures exceeding 580 °C. The temperature-dependent behavior was also traced by photoemission electron microscopy up to 460 °C. At high temperatures, the thermoelectric properties are superior to those of pure germanium antimony tellurides obtained by comparable syntheses; a maximal zT value of 1.83 for Cu2Ge16Sb2Te20 is reached at 500 °C. The application of an effective mass model reveals optimal charge carrier concentrations for all three compositions investigated. The p-type Cu2Ge16Sb2Te20 material was used in combination with PbTe:In (n-type) to construct a thermoelectric module. Concludingly, the measurement of the Hall effect that suggests no significant changes in Cu-doping levels of the matrix with temperature application of grain boundary optimization and a temperature-induced reset of the microstructure are proposed as strategies for overcoming material degradation upon applying electrical currents.

MICROTOMOGRAFÍA DE RAYOS X PARA CARACTERIZAR VOLUMEN DEL CANAL RADICULAR EXTRAÍDO EN INSTRUMENTACIÓN ENDODÓNTICA

During the last decades, the analytical techniques of X-ray absorption contrast imaging have systematically gained greater relevance, mainly due to the ability to attain non-destructive exploration of the sample interior. The significant improvement in spatial resolution offered by X-ray micro-tomography, as compared to conventional computed tomography, has motivated its insertion in many biomedical fields, among which dentistry stands out. Particularly, for endodontics, microCT appears as a method of remarkable potential interest to study procedures involved in root canal treatments, where one of the main needs is the anatomical characterization of the root canal in the teeth. The present work reports on the adaptation of the microCT equipment of the LIIFAMIRx⃝laboratory at the E. Gaviola Physics Institute, CONICET and UNC, thus allowing to acquire of radiographic images of dental samples of interest, to be later used in the implementation of algorithms, intended to tomographic reconstruction and volume segmentation. As a result, radiographic images of premolar teeth were obtained with good contrast between the different materials present, and three-dimensional representations, whose visualization is comparable with the real samples. Moreover, it was possible to characterize the root canal volume of the tooth both in its natural form and after having undergone the instrumentation process in which the pulp tissue is extracted.

Observation of aluminum interaction with the binder melt layer using high-speed synchrotron-based phase contrast imaging

Particle interactions with the binder melt layer are a major factor in the combustion efficiency and stability of the propellant in a solid rocket motor. Metal particles tend to agglomerate on the surface of burning solid propellants, inhibiting the combustion process. Therefore, reduction of molten aluminum agglomeration in a solid rocket motor is vital to the improvement of solid rocket propulsion system performance. In other work, quenched samples have been used to study the impact of how metal particles alter the flow properties of the molten propellant surface. In-situ optical measurements have also been attempted for these particle-condensed phase interactions, but with little success due to the opacity and strong gradients within the flame. This study expanded on previous work using synchrotron–based x-rays to directly image these aluminum agglomerates as they interacted with the binder. X-ray absorption and phase contrast in the images allowed for the direct measurement of the particle size in combusting propellants in-situ at typical rocket pressures. Particle size distributions were collected in an optically accessible combustion vessel over a pressure range of 1.4- to 6.9-MPa (200- to 1000-psig). This investigation measured the aggregate sizes ranging from 300-to 650-µm at a 6.9 MPa chamber pressure. Interestingly, the lowest binder melting temperature produced the longest aluminum chaining at 1.1 mm and the highest binder melting temperature produced the second longest chain at 524 µm long. The study observed aluminum interactions with the binder melt layer on the propellant surface that may be a contributing factor in a plateau propellant. Additionally, data pointed to possible relationships between binder viscosity, burning rate, aluminum clusters, and chain formation in a solid propellant. The study concluded with collecting data on the molten aluminum volumetric changes in a propellant environment, thus defining a starting particle diameter for particle regression rates. Collecting the regression rates also provided information on the evaporation rate of aluminum, which burned in the propellant flame. All of these data are critical for understanding the combustion of aluminum-based solid rocket propellants and outlines knowledge gaps that need additional data.

Operando X-ray absorption tomography for the characterization of lithium metal electrode morphology and heterogeneity in a liquid Li/S cell

Lithium/sulfur batteries have been under intense study for the last two decades, due to the high specific capacity promised by elemental sulfur as an active material. Sulfur is also cheap, abundant and non-toxic compared to conventional transition metal oxides. The Li/S electrochemical cell is traditionally composed of a sulfur-based electrode, an organic liquid electrolyte and a lithium metal electrode. Lithium metal technologies have received a renewed interest, due to the light weight and low operating voltage of the lithium electrode, which makes it the ultimate choice to be combined with high-energy positive electrode materials. In this paper, operando X-ray absorption and phase contrast tomography were employed to characterize the lithium metal electrode morphology and heterogeneity in a liquid Li/S cell. It was observed that oxidation of the lithium foil occurs in a heterogeneous fashion with pit formation from the beginning of discharge, with the pits growing in diameter, depth and quantity during the discharge. Using Faraday's law, the local current density distribution was calculated to confirm the strongly heterogeneous behavior of the lithium metal electrode. We demonstrate that decreasing the current density leads to lithium stripping/plating occurring more homogenously, with the formation of a smaller number of pits. • X-ray absorption tomography is a powerful tool to characterize the lithium. • Presence of large number of pits during lithium oxidation at high current density. • Determination of the local current density distribution. • Lithium heterogeneity starts at the beginning of the cell life.

Nucleation bursts of primary intermetallic crystals in a liquid Al alloy studied using in situ synchrotron X-ray radiography

The nucleation of primary Pt-rich intermetallic compound (IMC) crystals was studied in a model Al-Pt-Er alloy as an analogue to Al13Fe4 that forms in commercial Al alloys. The Pt-rich IMCs provided strong X-ray absorption contrast that allowed earlier detection of formation events and the resolution of solute diffusion fields. Crystal formation behaviour was investigated during directional and isothermal solidification when the alloy was inoculated with TiB2 particles at cooling rates of 0.1 Ks−1 to 8 Ks−1 using in situ synchrotron X-ray radiography. Different from previous studies that concerned disordered, solid solution phases such as α-Al dendrites, for the first time nucleation bursts of ordered compound crystals were observed, where the nucleation of the IMC crystals proceeded in distinct cascades (in the time domain) or waves (in the spatial domain), the magnitude of which increased with increasing cooling rate and particularly with decreasing thermal gradient in the melt. Comparing the crystal number density with the estimated number density of TiB2 particles suggested that the IMC crystals nucleated only on the most potent TiB2 particles, accounting for ∼0.5% of the total TiB2 number density in the melt. The effect of the thermal gradient and cooling rate on the magnitude of the nucleation waves and the IMC number density was revealed in terms of the available undercooling in the liquid in front of an individual IMC and the solute depleted liquid fraction that arose from the interaction of an ensemble of IMC crystals.

Relation between dark-field images derived using X-Ray Talbot–Lau interferometer and carbon fiber distribution in CFRP

This study proposes a model that relates the carbon fiber arrangement and orientation in CFRP to the dark-field images captured by X-ray Talbot-Lau interferometer (TLI). X-ray TLI visualizes X-ray phase contrast, which is more sensitive to light elements such as carbon, than conventional X-ray absorption contrast. By using TLI, novel non-destructive inspection (NDI) technique for CFRP reinforced by distributed discontinuous carbon fibers, which precisely evaluates local orientation and distribution of fibers in large area, can be developed. The model proposed in this study forms the basis of such NDI technique. In this paper, the model is proposed first, and material parameters needed for the model are then identified from the TLI dark-field images of the multi-fiber composite (MFC) specimens. The proposed model is validated by comparing the dark-field images simulated by the model to those experimentally measured by TLI.

Quantitative conversion of biomass in giant DNA virus infection

Bioconversion of organic materials is the foundation of many applications in chemical engineering, microbiology and biochemistry. Herein, we introduce a new methodology to quantitatively determine conversion of biomass in viral infections while simultaneously imaging morphological changes of the host cell. As proof of concept, the viral replication of an unidentified giant DNA virus and the cellular response of an amoebal host are studied using soft X-ray microscopy, titration dilution measurements and thermal gravimetric analysis. We find that virions produced inside the cell are visible from 18 h post infection and their numbers increase gradually to a burst size of 280–660 virions. Due to the large size of the virion and its strong X-ray absorption contrast, we estimate that the burst size corresponds to a conversion of 6–12% of carbonaceous biomass from amoebal host to virus. The occurrence of virion production correlates with the appearance of a possible viral factory and morphological changes in the phagosomes and contractile vacuole complex of the amoeba, whereas the nucleus and nucleolus appear unaffected throughout most of the replication cycle.

Synchrotron X-ray induced acoustic imaging

X-ray induced acoustic imaging (XAI) is an emerging biomedical imaging technique that can visualize X-ray absorption contrast at ultrasound resolution with less ionizing radiation exposure than conventional X-ray computed tomography. So far, medical linear accelerators or industrial portable X-ray tubes have been explored as X-ray excitation sources for XAI. Here, we demonstrate the first feasible synchrotron XAI (sXAI). The synchrotron generates X-rays, with a dominant energy of 4 to 30 keV, a pulse-width of 30 ps, a pulse-repetition period of 2 ns, and a bunch-repetition period of 940 ns. The X-ray induced acoustic (XA) signals are processed in the Fourier domain by matching the signal frequency with the bunch-repetition frequency. We successfully obtained two-dimensional XA images of various lead targets. This novel sXAI tool could complement conventional synchrotron applications.

Method of single exposure phase contrast imaging without analyser grating

X-ray differential phase contrast imaging technology can reveal the weakly absorbing fine structure which cannot be observed by the conventional X-ray absorption contrast imaging. Hence, it has potential applications in many fields such as medical science, and material science. But in the traditional X-ray grating differential phase contrast imaging system, the analyser grating is used as a spatial filter, and needs to be phase stepped, then multiple exposures are required for information extraction. Thus this leads to high-dose radiation exposure and low efficiency of X-ray utilization. All these disadvantages limit its application in various disciplines. In order to cope with the above issues, a new algorithm based on single-shot grating differential phase contrast imaging system without analyzer grating is proposed. In such a system the absorption, refraction and scattering information can be obtained from one projective image of the sample acquired by a high-resolution detector. The reliability of this new algorithm is confirmed by numerical simulation. Compared with the phase stepping algorithm, the proposed algorithm can provide very accurate and reliable information extraction results without requiring the grating period to match with detector pixel size. It facilitates the reduction of the radiation damage to sample. We emphasize that this method is highly compatible with the future X-ray phase contrast imaging clinical applications.

X-Ray-Induced Acoustic Computed Tomography (XACT): Initial Experiment on Bone Sample.

X-ray-induced acoustic computed tomography (XACT) is a unique hybrid imaging modality that combines high X-ray absorption contrast with high ultrasonic resolution. X-ray radiography and computerized tomography (CT) are currently the gold standards for 2-D and 3-D imaging of skeletal tissues though there are important properties of bone, such as elasticity and speed of sound (SOS), that these techniques cannot measure. Ultrasound is capable of measuring such properties though current clinical ultrasound scanners cannot be used to image the interior morphology of bones because they fail to address the complicated physics involved for exact image reconstruction; bone is heterogeneous and composed of layers of both cortical and trabecular bone, which violates assumptions in conventional ultrasound imaging of uniform SOS. XACT, in conjunction with the time-reversal algorithm, is capable of generating precise reconstructions, and by combining elements of both X-ray and ultrasound imaging, XACT is potentially capable of obtaining more information than any single of these techniques at low radiation dose. This article highlights X-ray-induced acoustic detection through linear scanning of an ultrasound transducer and the time-reversal algorithm to produce the first-ever XACT image of a bone sample. The results of this study should prove to enhance the potential of XACT imaging in the evaluation of bone diseases for future clinical use.

3-D X-Ray-Induced Acoustic Computed Tomography With a Spherical Array: A Simulation Study on Bone Imaging.

X-ray-induced acoustic computed tomography (XACT) is a promising imaging modality combining high X-ray absorption contrast with the 3-D propagation advantages provided by high-resolution ultrasound waves. The purpose of this study was to optimize the configuration of a 3-D XACT imaging system for bone imaging. A 280 ultrasonic sensors with peak frequency of 10 MHz was designed to distribute on a spherical surface to optimize the 3-D volumetric imaging capability. We performed both theoretical calculations and simulations of this optimized XACT imaging configuration on a mouse-sized digital phantom containing various X-ray absorption coefficients. Iteration algorithm based on total variation has been used for 3-D XACT image reconstruction. The spatial resolution of imaging was estimated to about [Formula: see text] along both axial and lateral directions. We simulate XACT imaging of bone microstructures using digital phantoms generated from micro-CT images of real biological samples, showing that XACT imaging can provide high-resolution imaging of the mouse paw. Results of this study will greatly enhance the potential of XACT imaging in the evaluation of bone diseases for future clinical use.

Coating Distribution Analysis on Gas Diffusion Layers for Polymer Electrolyte Fuel Cells by Neutron and X-ray High-Resolution Tomography.

Coating load and distribution in gas diffusion layers (GDLs) for polymer electrolyte fuel cells (PEFCs) have a major influence on mass transport losses. To be able to optimize the coating distribution and get more accurate data about the influence of the coating on the PEFC performance, better characterization techniques are necessary. Common analysis techniques are limited to selected sections of the material, or they are not sensitive to small amounts of coating. We propose a new methodology to get a complete description of the coating distribution and the GDL structure by combining high-resolution X-ray tomography with high-resolution neutron tomography. Using an isotopic gadolinium staining method to enhance the neutron and X-ray absorption contrast, lower quantities of coating can be detected. The combination of both imaging techniques allows for a more detailed analysis of the coating distribution.

Provenance of uranium particulate contained within Fukushima Daiichi Nuclear Power Plant Unit 1 ejecta material

Here we report the results of multiple analytical techniques on sub-mm particulate material derived from Unit 1 of the Fukushima Daiichi Nuclear Power Plant to provide a better understanding of the events that occurred and the environmental legacy. Through combined x-ray fluorescence and absorption contrast micro-focused x-ray tomography, entrapped U particulate are observed to exist around the exterior circumference of the highly porous Si-based particle. Further synchrotron radiation analysis of a number of these entrapped particles shows them to exist as UO2—identical to reactor fuel, with confirmation of their nuclear origin shown via mass spectrometry analysis. While unlikely to represent an environmental or health hazard, such assertions would likely change should break-up of the Si-containing bulk particle occur. However, more important to the long-term decommissioning of the reactors at the FDNPP (and environmental clean-upon), is the knowledge that core integrity of reactor Unit 1 was compromised with nuclear material existing outside of the reactors primary containment.

Hard and soft X-ray imaging to resolve human ovarian cortical structures.

Laboratory and synchrotron X-ray tomography are powerful tools for non-invasive studies of biological samples at micrometric resolution. In particular, the development of phase contrast imaging is enabling the visualization of sample details with a small range of attenuation coefficients, thus allowing in-depth analyses of anatomical and histological structures. Reproductive medicine is starting to profit from these techniques, mainly applied to animal models. This study reports the first imaging of human ovarian tissue where the samples consisted of surgically obtained millimetre fragments, properly fixed, stained with osmium tetroxide and included in epoxydic resin. Samples were imaged by the use of propagation phase contrast synchrotron radiation micro-computed tomography (microCT), obtained at the SYRMEP beamline of Elettra light source (Trieste, Italy), and X-ray absorption microCT at the Theoretical Biology MicroCT Imaging Laboratory in Vienna, Austria. The reconstructed microCT images were compared with the soft X-ray absorption and phase contrast images acquired at the TwinMic beamline of Elettra in order to help with the identification of structures. The resulting images allow the regions of the cortex and medulla of the ovary to be distinguished, identifying early-stage follicles and visualizing the distribution of blood vessels. The study opens to further application of micro-resolved 3D imaging to improve the understanding of human ovary's structure and support diagnostics as well as advances in reproductive technologies.

Simulated grating-based x-ray phase contrast images of CFRP-like objects

Because of their microstructure, carbon fibre reinforced polymers outperform conventional materials in many aspects. These materials are, given the low x-ray absorption contrast they provide, ideally suited for phase contrast x-ray computed tomography. For system prototyping and for benchmarking and testing acquisition and reconstruction procedures, computer simulations are a valuable tool. In this paper, we propose the application of an alternative simulation strategy that unites Monte Carlo simulations with numerical wave optics and involves detailed modelling of the internal carbon fibre reinforced polymer structure down to the individual fibre scale.

Fast X-ray Differential Phase Contrast Imaging with One Exposure and without Movements

Grating interferometry X-ray differential phase contrast imaging (GI-XDPCI) has provided enhanced imaging contrast and attracted more and more interests. Currently the low imaging efficiency and increased dose remain to be the bottlenecks in the engineering applications of GI-XDPCI. Different from the widely-used X-ray absorption contrast imaging (XACI) found in hospitals and factories, GI-XDPCI involves a grating stepping procedure that is time-consuming and leads to a significantly increased X-ray exposure time. In this paper, we report a fast GI-XDPCI method without movements by designing a new absorption grating. There is no grating stepping in this approach, and all components remain stationary during the imaging. Three kinds of imaging contrasts are provided with greatly reduced time. This work is comprised of a numerical study of the method and its verification using a sub-set of the dataset measured with a standard GI-XDPCI system at the beam line BL13W1 of the Shanghai Synchrotron Radiation Facility (SSRF). These results have validated the presented method.

Evaluation of Usability on Mobile Detector X-ray Absorption, scattering, and Phased Image Phantom

Existing X-ray medical imaging acquired the image data of X-ray absorption difference using the difference in density of the subject tissue. X-ray scattering and phase contrast imaging technology is a technology that dramatically increases boundary information between homogeneous materials of similar density using scattering and phase contrast information. To acquire and evaluate absorption, scattering, and phase contrast images, using the phantom made of polyethylene, on a round rod with a diameter of 3×1cm, a hole with a diameter of 0.5cm was drilled on 5 round rods, and the medical phantom was produced by sealing with sodium chloride, neon, calcium, phosphorus, and selenium powder. At a distance of 40cm from the focus, the distribution of absorbed doses have shown 1, 277 ± 0.31μGy in the center area. The measurement dose in the anode side direction was 110.1 ± 0.35μGy and the cathode side direction was 117.7 ± 0.77μGy. It has shown dose inequality that depends on the geometry of the target. It has shown similar tendency in 60cm and 80cm Compared with absorption images in graphite materials, it was confirmed that scattering and phase contrast images were showing relatively high image information. These results are expected to be utilized as an important basic data for reducing medical exposure dose and acquiring, evaluating and utilizing X-ray absorption, scattering and phase contrast images.

Virtual subpixel approach for single-mask phase-contrast imaging using Timepix3

X-ray phase contrast imaging provides a method to distinguish materials with similar density and effective atomic number, which otherwise would be difficult using conventional X-ray absorption contrast. In recent years, multiple methods have been developed to acquire X-ray phase contrast images using incoherent laboratory sources. The single mask edge illumination setup has been demonstrated as a possible candidate for large scale applications due to its relaxed restrictions on longitudinal coherence and mask alignment, and for its ability to do bi-directional phase contrast images in a single sample exposure. Unfortunately, the single mask edge illumination setup's refraction sensitivity, and thereby signal to noise, is limited by detector artifacts. Furthermore, it requires multiple exposures to perform dark-field imaging, a method that enables imaging of micro-structures smaller than the image resolution. We propose using an Advapix detector with Timepix3 pixel-readout chip in a single mask imaging setup to improve signal to noise ratio in phase contrast images. This is achieved using the Timepix3 chip's ability to simultaneously acquire fast time of arrival and time over threshold measurement of single photon events, which enables sub-pixel identification of individual photons. In this paper, we demonstrate that signal to noise ratio can be improved by at least 67± 5 % using subpixel identification of single photons compared to conventional acquisitions methods. Thereby the required sample dose can be reduced considerably. This shows that there is a great potential in using Timepix3 chip to improve x-ray phase contrast imaging. Further, the results indicate the possibility for dark field imaging in a single sample exposure using Timepix3 in a single mask edge illumination setup.

Visualizing the 3D cytoarchitecture of the human cochlea in an intact temporal bone using synchrotron radiation phase contrast imaging.

The gold standard method for visualizing the pathologies underlying human sensorineural hearing loss has remained post-mortem histology for over 125 years, despite awareness that histological preparation induces severe artifacts in biological tissue. Historically, the transition from post-mortem assessment to non-invasive clinical biomedical imaging in living humans has revolutionized diagnosis and treatment of disease; however, innovation in non-invasive techniques for cellular-level intracochlear imaging in humans has been difficult due to the cochlea's small size, complex 3D configuration, fragility, and deep encasement within bone. Here we investigate the ability of synchrotron radiation-facilitated X-ray absorption and phase contrast imaging to enable visualization of sensory cells and nerve fibers in the cochlea's sensory epithelium in situ in 3D intact, non-decalcified, unstained human temporal bones. Our findings show that this imaging technique resolves the bone-encased sensory epithelium's cytoarchitecture with unprecedented levels of cellular detail for an intact, unstained specimen, and is capable of distinguishing between healthy and damaged epithelium. All analyses were performed using commercially available software that quickly reconstructs and facilitates 3D manipulation of massive data sets. Results suggest that synchrotron radiation phase contrast imaging has the future potential to replace histology as a gold standard for evaluating intracochlear structural integrity in human specimens, and motivate further optimization for translation to the clinic.