Characterization of Pt-coated twin paraboloidal laboratory capillary high energy X-ray optics.

Novel focusing optics composed of twin paraboloidal capillaries coated with Pt, for laboratory X-ray sources are presented and characterized. The optics are designed to focus the X-rays, resulting in an achromatic focused beam with photon energies up to 40 keV. The performance of the optics under different operational conditions is studied by comparing the energy-photon count spectra of the direct and focused beams. Based on these analyses, the optics gain and efficiency as a function of photon energy are determined. A focal spot of 8.5 µm with a divergence angle of 0.59° is observed. The obtained characteristics are discussed and related to theoretical considerations. Moreover, the suitability and advantages of the present optics for X-ray microdiffraction is demonstrated using polycrystalline aluminium. Finally, possibilities for further developments are suggested.

Micro X-ray fluorescence reveals pore space details and spatially-resolved porosity of rock-based microfluidic devices.

Characterization of microscopic details of the fabric of mudstones and shales (i.e., structure and composition) is important to understand their storage and transport properties. Current characterization methods struggle to probe reliably multiple scales of interest (e.g., pore and fracture) and measure properties at the finest resolution under representative in situ conditions. Micro X-ray fluorescence (µXRF) is a high-performance imaging technique that produces elemental images at sub-10 µm spatial resolution and could offer insight into a diversity of shale properties, such as mineral composition, porosity, and in situ pressure gradients. This study designed and carried out a porosity mapping protocol using model and real-rock microfluidic devices and contrast fluids. Etched silicon micromodels with real-rock pore network patterns served as ideal models to establish a proof of concept. Measurements were performed on a novel µXRF microscope not powered by synchrotron radiation. We registered the µXRF datasets with the binary rock masks used for micromodel fabrication and applied segmentation algorithms to compare porosities. We assessed expected advantages and limitations through a sensitivity analysis and beam study. µXRF is an important new imaging technique for microfluidic applications.

In situ visualization of multicomponents coevolution in a battery pouch cell.

Lithium-ion battery (LIB) is a broadly adopted technology for energy storage. With increasing demands to improve the rate capability, cyclability, energy density, safety, and cost efficiency, it is crucial to establish an in-depth understanding of the detailed structural evolution and cell-degradation mechanisms during battery operation. Here, we present a laboratory-based high-resolution and high-throughput X-ray micro-computed laminography approach, which is capable of in situ visualizing of an industry-relevant lithium-ion (Li-ion) pouch cell with superior detection fidelity, resolution, and reliability. This technique enables imaging of the pouch cell at a spatial resolution of 0.5 µm in a laboratory system and permits the identification of submicron features within cathode and anode electrodes. We also demonstrate direct visualization of the lithium plating in the imaged pouch cell, which is an important phenomenon relevant to battery fast charging and low-temperature cycling. Our development presents an avenue toward a thorough understanding of the correlation among multiscale structures, chemomechanical degradation, and electrochemical behavior of industry-scale battery pouch cells.

High-resolution multicontrast tomography with an X-ray microarray anode-structured target source.

Multicontrast X-ray imaging with high resolution and sensitivity using Talbot-Lau interferometry (TLI) offers unique imaging capabilities that are important to a wide range of applications, including the study of morphological features with different physical properties in biological specimens. The conventional X-ray TLI approach relies on an absorption grating to create an array of micrometer-sized X-ray sources, posing numerous limitations, including technical challenges associated with grating fabrication for high-energy operations. We overcome these limitations by developing a TLI system with a microarray anode-structured target (MAAST) source. The MAAST features an array of precisely controlled microstructured metal inserts embedded in a diamond substrate. Using this TLI system, tomography of a Drum fish tooth with high resolution and tri-contrast (absorption, phase, and scattering) reveals useful complementary structural information that is inaccessible otherwise. The results highlight the exceptional capability of high-resolution multicontrast X-ray tomography empowered by the MAAST-based TLI method in biomedical applications.

Metrology of a Focusing Capillary Using Optical Ptychography.

The focusing property of an ellipsoidal monocapillary has been characterized using the ptychography method with a 405 nm laser beam. The recovered wavefront gives a 12.5×10.4µm2 focus. The reconstructed phase profile of the focused beam can be used to estimate the height error of the capillary surface. The obtained height error shows a Gaussian distribution with a standard deviation of 1.3 µm. This approach can be used as a quantitative tool for evaluating the inner functional surfaces of reflective optics, complementary to conventional metrology methods.

Quantitative analysis of a micro array anode structured target for hard x-ray grating interferometry.

Talbot-Lau interferometry (TLI) provides additional contrast modes for x-ray imaging that are complementary to conventional absorption radiography. TLI is particularly interesting because it is one of the few practical methods for realizing phase contrast with x-rays that is compatible with large-spot high power x-ray sources. A novel micro array anode structured target (MAAST) x-ray source offers several advantages for TLI over the conventional combination of an extended x-ray source coupled with an absorption grating including higher flux and larger field of view, and these advantages become more pronounced for x-ray energies in excess of 30 keV. A Monte Carlo simulation was performed to determine the optimal parameters for a MAAST source for use with TLI. It was found that the both spatial distribution of x-ray production and the number of x-ray produced in the MAAST have a strong dependence on the incidence angle of the electron beam.

Design optimization of a periodic microstructured array anode for hard x-ray grating interferometry.

Talbot-Lau grating interferometer (TLGI) has great advantages in x-ray imaging contrasts, especially for low-Z materials, over conventional absorption contrast. A microstructured array anode target (MAAT) source offers significantly higher imaging throughput than the combination of an extended x-ray source paired with an absorption grating (also known as source grating). The performance of the MAAT source can be optimized with respect to the areal density, dimensions, and choice of material for the microstructured metal inserts (MMI) and the substrate in which they are embedded. In this paper, we analyze the x-ray generation efficiency per incident electron, relative fraction of x-rays generated by MMI and substrate, x-ray spectrum, and angular distribution via Monte Carlo simulation. Based on the simulation results, the optimal parameters are obtained for a MAAT with incident electron energies from 30 keV to 120 keV. The corresponding temperature distribution within the MAAT is also simulated for the optimal set of the parameters via finite element analysis. As demonstrated by the thermal analysis data, the maximum allowable electron-beam power loading was derived that allows a stable operation of the transmission MAAT.

A mixed reality approach for stereo-tomographic quantification of lung nodules.

To reduce the radiation dose and the equipment cost associated with lung CT screening, in this paper we propose a mixed reality based nodule measurement method with an active shutter stereo imaging system. Without involving hundreds of projection views and subsequent image reconstruction, we generated two projections of an iteratively placed ellipsoidal volume in the field of view and merging these synthetic projections with two original CT projections. We then demonstrated the feasibility of measuring the position and size of a nodule by observing whether projections of an ellipsoidal volume and the nodule are overlapped from a human observer's visual perception through the active shutter 3D vision glasses. The average errors of measured nodule parameters are less than 1 mm in the simulated experiment with 8 viewers. Hence, it could measure real nodules accurately in the experiments with physically measured projections.

Mineral density volume gradients in normal and diseased human tissues.

Clinical computed tomography provides a single mineral density (MD) value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca) to phosphorus (P) and Ca to zinc (Zn) elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT) benchtop unit were correlated with elemental mapping obtained from a microprobe X-ray fluorescence (XRF) using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males) contained significant mineral density variations (enamel: 2820-3095 mg/cc, bone: 570-1415 mg/cc, cementum: 1240-1340 mg/cc, dentin: 1480-1590 mg/cc, cementum affected by periodontitis: 1100-1220 mg/cc, hypomineralized carious dentin: 345-1450 mg/cc, hypermineralized carious dentin: 1815-2740 mg/cc, and dental calculus: 1290-1770 mg/cc). A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49), hypomineralized dentin (0.32-0.46), cementum (1.51), and bone (1.68) were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765) and in cementum (595-990), highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations.

Scattering imaging method in transmission x-ray microscopy.

We present a x-ray microscopy technique based on structured illumination in a microscope that characterizes the size of the subresolution-limit features. The technique is effective for characterizing fine structures substantially beyond the Rayleigh resolution of the microscope. We carried out optical experiments to demonstrate the basic principle of this new technique. Experimental results show good agreement with theoretical predictions. This technique should find a wide range of important imaging applications with a feature size down to nanometer scale, such as oil and gas reservoir rocks, advanced composites, and functional nanodevices and materials.

Advantages of intermediate X-ray energies in Zernike phase contrast X-ray microscopy.

Understanding the hierarchical organizations of molecules and organelles within the interior of large eukaryotic cells is a challenge of fundamental interest in cell biology. Light microscopy is a powerful tool for observations of the dynamics of live cells, its resolution attainable is limited and insufficient. While electron microscopy can produce images with astonishing resolution and clarity of ultra-thin (<1 µm thick) sections of biological specimens, many questions involve the three-dimensional organization of a cell or the interconnectivity of cells. X-ray microscopy offers superior imaging resolution compared to light microscopy, and unique capability of nondestructive three-dimensional imaging of hydrated unstained biological cells, complementary to existing light and electron microscopy. Until now, X-ray microscopes operating in the "water window" energy range between carbon and oxygen k-shell absorption edges have produced outstanding 3D images of cryo-preserved cells. The relatively low X-ray energy (<540 eV) of the water window imposes two important limitations: limited penetration (<10 µm) not suitable for imaging larger cells or tissues, and small depth of focus (DoF) for high resolution 3D imaging (e.g., ~1 µm DoF for 20 nm resolution). An X-ray microscope operating at intermediate energy around 2.5 keV using Zernike phase contrast can overcome the above limitations and reduces radiation dose to the specimen. Using a hydrated model cell with an average chemical composition reported in literature, we calculated the image contrast and the radiation dose for absorption and Zernike phase contrast, respectively. The results show that an X-ray microscope operating at ~2.5 keV using Zernike phase contrast offers substantial advantages in terms of specimen size, radiation dose and depth-of-focus.

A 30 nm-resolution hard X-ray microscope with X-ray fluorescence mapping capability at BSRF.

A full-field transmission X-ray microscope (TXM) operating continuously from 5 keV to 12 keV with fluorescence mapping capability has been designed and constructed at the Beijing Synchrotron Radiation Facility, a first-generation synchrotron radiation facility operating at 2.5 GeV. Spatial resolution better than 30 nm has been demonstrated using a Siemens star pattern in both absorption mode and Zernike phase-contrast mode. A scanning-probe mode fluorescence mapping capability integrated with the TXM has been shown to provide 50 p.p.m. sensitivity for trace elements with a spatial resolution (limited by probing beam spot size) of 20 µm. The optics design, testing of spatial resolution and fluorescence sensitivity are presented here, including performance measurement results.

Nanoscale X-ray microscopic imaging of mammalian mineralized tissue.

A novel hard transmission X-ray microscope (TXM) at the Stanford Synchrotron Radiation Lightsource operating from 5 to 15 keV X-ray energy with 14 to 30 microm2 field of view has been used for high-resolution (30-40 nm) imaging and density quantification of mineralized tissue. TXM is uniquely suited for imaging of internal cellular structures and networks in mammalian mineralized tissues using relatively thick (50 microm), untreated samples that preserve tissue micro- and nanostructure. To test this method we performed Zernike phase contrast and absorption contrast imaging of mouse cancellous bone prepared under different conditions of in vivo loading, fixation, and contrast agents. In addition, the three-dimensional structure was examined using tomography. Individual osteocytic lacunae were observed embedded within trabeculae in cancellous bone. Extensive canalicular networks were evident and included processes with diameters near the 30-40 nm instrument resolution that have not been reported previously. Trabecular density was quantified relative to rod-like crystalline apatite, and rod-like trabecular struts were found to have 51-54% of pure crystal density and plate-like areas had 44-53% of crystal density. The nanometer resolution of TXM enables future studies for visualization and quantification of ultrastructural changes in bone tissue resulting from osteoporosis, dental disease, and other pathologies.

Structure, chemical composition and mechanical properties of coronal cementum in human deciduous molars.

OBJECTIVES: It was hypothesized that the coronal cementum containing collagen forms a weak junction with enamel unlike the well integrated DEJ and CDJ. METHODS: The hypothesis was investigated in two parts: (1) evaluate the structure, chemical composition and mechanical properties of coronal cementum and its junction with enamel using scanning electron microscopy, micro-X-ray computed tomography, and atomic force microscopy. The chemical composition and mechanical properties were determined by evaluating the spatial variations of inorganic (PO(4)(3-)nu(1) mode at 960 cm(-1)) and organic (C-H deformation at 1452 cm(-1); C-H stretch at 2940 cm(-1)) contents using Raman microspectroscopy and elastic modulus and hardness values using nanoindentation. (2) Estimate the strength and evaluate the microstructure of coronal cementum interface with enamel using SEM and MicroXCT. RESULTS AND CONCLUSIONS: Coronal cementum is heterogeneous because it is a combination of laminar acellular afibrillar cementum and acellular extrinsic fiber cementum with relatively higher organic content. It integrates micromechanically via a scallop-like weak interface with enamel unlike the biomechanically efficient DEJ and CDJ and is continuous with primary root cementum. A single tooth could exhibit all three types of cementum enamel junctions; an overlap, butt and a gap depending on the sectioning plane. The elastic modulus of coronal cementum (11.0+/-5.8 GPa) is significantly lower (p<0.05; Student's t-test with 95% confidence interval) than primary cementum (15.8+/-5.3 GPa).

Structure, chemical composition and mechanical properties of human and rat cementum and its interface with root dentin.

This work seeks to establish comparisons of the physical properties of rat and human cementum, root dentin and their interface, including the cementum-dentin junction (CDJ), as a basis for future studies of the entire periodontal complex using rats as animal models. In this study the structure, site-specific chemical composition and mechanical properties of cementum and its interface with root dentin taken from 9- to 12-month-old rats were compared to the physiologically equivalent 40- to 55-year-old human age group using qualitative and quantitative characterization techniques, including histology, atomic force microscopy (AFM), micro-X-ray computed tomography, Raman microspectroscopy and AFM-based nanoindentation. Based on results from this study, cementum taken from the apical third of the respective species can be represented as a woven fabric with radially and circumferentially oriented collagen fibers. In both species the attachment of cementum to root dentin is defined by a stiffness-graded interface (CDJ/cementum-dentin interface). However, it was concluded that cementum and the cementum-dentin interface from a 9- to 12-month-old rat could be more mineralized, resulting in noticeably decreased collagen fiber hydration and significantly higher modulus values under wet conditions for cementum and CDJ (E(rat-cementum)=12.7+/-2.6 GPa; E(rat-CDJ)=11.6+/-3.2 GPa) compared to a 40- to 55-year-old human (E(human-cementum)=3.73+/-1.8 GPa; E(human-CDJ)=1.5+/-0.7 GPa). The resulting data illustrated that the extensions of observations made from animal models to humans should be justified with substantial and equivalent comparison of data across age ranges (life spans) of mammalian species.

High resolution hard x-ray microscope on a second generation synchrotron source.

A full-field, transmission x-ray microscope (TXM) operating in the energy range of 7-11 keV has been installed at the U7A beamline at the National Synchrotron Radiation Laboratory, a second generation synchrotron source operating at 0.8 GeV. Although the photon flux at sample position in the operating energy range is significantly low due to its relatively large emittance, the TXM can get high quality x-ray images with a spatial resolution down to 50 nm with acceptable exposure time. This TXM operates in either absorption or Zernike phase contrast mode with similar resolution. This TXM is a powerful analytical tool for a wide range of scientific areas, especially studies on nanoscale phenomena and structural imaging in biology, materials science, and environmental science. We present here the property of the x-ray source, beamline design, and the operation and key optical components of the x-ray TXM. Plans to improve the throughput of the TXM will be discussed.

Ellipsoidal and parabolic glass capillaries as condensers for x-ray microscopes.

Single-bounce ellipsoidal and paraboloidal glass capillary focusing optics have been fabricated for use as condenser lenses for both synchrotron and tabletop x-ray microscopes in the x-ray energy range of 2.5-18 keV. The condenser numerical apertures (NAs) of these devices are designed to match the NA of x-ray zone plate objectives, which gives them a great advantage over zone plate condensers in laboratory microscopes. The fabricated condensers have slope errors as low as 20 murad rms. These capillaries provide a uniform hollow-cone illumination with almost full focusing efficiency, which is much higher than what is available with zone plate condensers. Sub-50 nm resolution at 8 keV x-ray energy was achieved by utilizing this high-efficiency condenser in a laboratory microscope based on a rotating anode generator.

Achromatic Fresnel optics for wideband extreme-ultraviolet and X-ray imaging.

Advances in extreme-ultraviolet (EUV) and X-ray optics are providing powerful new capabilities in high-resolution imaging and trace-element analysis of microscopic specimens, and the potential for fabricating devices of smaller critical dimensions in next-generation integrated circuit lithography. However, achieving the highest resolution with such optics usually requires the illuminating EUV or X-ray beam to be highly monochromatic. It would therefore be highly desirable to have large-field-of-view, sub-100-nm resolution optics that are achromatic to a significant degree, allowing more light to be utilized from broader bandwidth sources such as laser-produced plasmas. Here we report an achromatic Fresnel optical system for EUV or X-ray radiation that combines a Fresnel zone plate with a refractive lens with opposite chromatic aberration. We use the large anomalous dispersion property of the refractive lens material near an absorption edge to make its fabrication practical. The resulting structure can deliver a resolution comparable to that of the Fresnel zone plates that have achieved the highest resolution (25 nm; ref. 3) in the entire electromagnetic spectrum, but with an improvement of two or more orders of magnitude in spectral bandwidth.

The direct mapping of the uptake of platinum anticancer agents in individual human ovarian adenocarcinoma cells using a hard X-ray microprobe.

Uptake of platinum-based anticancer compounds into individual human ovarian andenocarcinoma cells was measured using an X-ray microprobe. The uptake of cisplatin, a platinum-based compound, in drug-resistant cells is decreased by approximately 50% after 24 h, compared with the uptake of the drug in nonresistant cells over the same time period. The Pt103 derivative of the drug, in contrast, showed an increased uptake by an order of magnitude in resistant cells over the same time period. Increased uptake appears to allow Pt103 to overcome the resistance mechanism developed by the cell. This work additionally shows that the X-ray microprobe is able to directly quantify Pt drug uptake on a subcellular level and can measure the mass of Pt down to a detectable limit of 20 attograms of Pt (2 x 10(-17) grams or 6 x 10(4) Pt atoms) in 1 s. Such exquisite elemental sensitivity combined with high spatial resolution paves the way for quantitative submicron three-dimensional mapping of elemental distributions within individual cells.