Conventional X-ray Source Research Articles

T staging esophageal tumors with x rays.

With histopathology results typically taking several days, the ability to stage tumors during interventions could provide a step change in various cancer interventions. X-ray technology has advanced significantly in recent years with the introduction of phase-based imaging methods. These have been adapted for use in standard labs rather than specialized facilities such as synchrotrons, and approaches that enable fast 3D scans with conventional x-ray sources have been developed. This opens the possibility to produce 3D images with enhanced soft tissue contrast at a level of detail comparable to histopathology, in times sufficiently short to be compatible with use during surgical interventions. In this paper we discuss the application of one such approach to human esophagi obtained from esophagectomy interventions. We demonstrate that the image quality is sufficiently high to enable tumor staging based on the x-ray datasets alone. Alongside detection of involved margins with potentially life-saving implications, staging tumors intra-operatively has the potential to change patient pathways, facilitating optimization of therapeutic interventions during the procedure itself. Besides a prospective intra-operative use, the availability of high-quality 3D images of entire esophageal tumors can support histopathological characterization, from enabling "right slice first time" approaches to understanding the histopathology in the full 3D context of the surrounding tumor environment.

Detection of gastrointestinal foreign bodies in pets using single-grid-based dark-field X-ray imaging

Gastrointestinal foreign bodies (GI-FBs) occur when pets consume non-digestible items that do not readily pass through the stomach or intestines. While some GI-FBs pass through, many become lodged along the gastrointestinal tract and cause discomfort, often leading to sickness. Conventional absorption-based radiography is widely used to detect GI-FBs in pets. However, detecting low-density FBs, such as wood, plastic, clothing, and sticks, is typically difficult using conventional radiography. This study presents a novel approach for detecting low-density GI-FBs in pets by using single-grid-based dark-field X-ray imaging (SG-DFXI). It obtains microstructural information from small-angle X-ray scattering (SAXS) of the sample using a conventional X-ray source and grid. SG-DFXI requires minimal exposure and system setup and is specifically utilized to detect low-density materials that are invisible when using conventional radiography. To validate the efficacy of the proposed method, an experiment was conducted on a mouse phantom attached to a wooden chopstick as a low-density GI-FB. Quantitative evaluation was performed using image quality metrics of the contrast-to-noise ratio (CNR) and relative contrast gain (RCG). The CNR value measured in the dark-field image obtained with an autocorrelation length of ξG = 294 nm was 4.59, approximately 5.4 times larger than that of the absorption image obtained in the same imaging setup. In addition, the RCG characteristics improved as the autocorrelation length of the system increased; the RCG value for ξG = 294 nm was 5.4, approximately 3.2 times larger than that for ξG = 194 nm. Thus, increasing the autocorrelation length of the system is critical to improve its ability to detect low-density FBs. Consequently, SG-DFXI appears to be a promising method that can be used effectively and easily to detect GI-FBs in pets, which are barely visible in absorption images.

Bottom-up Gold Filling of Trenches in Curved Wafers

A Bi3+ -stimulated Au electrodeposition process in slightly alkaline Na3AuSO32+Na2SO3 electrolytes has been previously demonstrated for void-free extreme bottom-up filling of high aspect ratio trenches in gratings that are key to advanced X-ray imaging technologies. Effective use of the full area of the gratings with conventional X-ray sources requires they have a finite radius of curvature to align the high aspect ratio Au-filled trenches with divergent X-rays. With that in mind, this work demonstrates bottom-up Au filling in gratings that are attached to curved holders. Contactless mapping of the Au-filled gratings captures residual curvature that is retained after their release from the curved holders (i.e., intrinsic curvature). X-ray diffraction captures the elastic strains in the Si underlying the Au-filled trenches of the grating. Complementary measurements on the surfaces of unpatterned Si wafers mounted on curved holders capture the actual curvatures and strains imposed in the mounted gratings. The gratings, either intrinsically curved or re-bent, provide high visibility across the entire field of view of an X-ray phase contrast imaging system with elastic strains substantially below those in planar gratings bent to the same radius.

Stability of electrons and X-rays generated in a pyroelectric accelerator

Conventional X-ray sources are far too bulky and require a high-power DC voltage. The pyroelectric X-ray generator technology has enabled us to develop portable, low-power X-ray sources for use in materials analysis, imaging, and other applications. Changing the temperature of single crystal lithium tantalate (LiTaO3) at moderate vacuum conditions gives an attractive possibility to generate and accelerate electron up to 100 keV. The electrons are ejected either from the crystal or from the target (depending on polarity). The electrons then generate X-rays via bremsstrahlung and characteristic X-ray emission processes. The aim of this experimental investigation is to explore the interesting feature of the pyroelectric accelerator that generates a monoenergetic electron flux with a stable value of peak energy for a long time. Here we present studies of features of electron flux in pyroelectric accelerator depending on the pressure of residual gas and the distance between the crystal and the target-collimator. We examine the correlation between monoenergetic electron production and avalanche discharge. We also studied outgassing from some accelerator components. The pyroelectric X-ray generator technology is currently being developed is a reliable, compact, stable, and reproducible X-ray source with controllable parameters, which does not require a high-power DC voltage or the use of hazardous (radioactive) materials.

Development and characterization of a versatile mini-beam collimator for pre-clinical photon beam irradiation.

Interest in spatial fractionation radiotherapy has exponentially increased over the last decade as a significant reduction of healthy tissue toxicity was observed by mini-beam irradiation. Published studies, however, mostly use rigid mini-beam collimators dedicated to their exact experimental arrangement such that changing the setup or testing new mini-beam collimator configurations becomes challenging andexpensive. In this work, a versatile, low-cost mini-beam collimator was designed and manufactured for pre-clinical applications with X-ray beams. The mini-beam collimator enables variability of the full width at half maximum (FWHM), the center-to-center distance (ctc), the peak-to-valley dose ratio (PVDR), and the source-to-collimator distance (SCD). The mini-beam collimator is an in-house development, which was constructed of 10× 40mm2 tungsten or brass plates. These metal plates were combined with 3D-printed plastic plates that can be stacked together in the desired order. A standard X-ray source was used for the dosimetric characterization of four different configurations of the collimator, including a combination of plastic plates of 0.5, 1, or 2mm width, assembled with 1 or 2mm thick metal plates. Irradiations were done at three different SCDs for characterizing the performance of the collimator. For the SCDs closer to the radiation source, the plastic plates were 3D-printed with a dedicated angle to compensate for the X-ray beam divergence, making it possible to study ultra-high dose rates of around 40Gy/s. All dosimetric quantifications were performed using EBT-XD films. Additionally, in vitro studies with H460 cells were carriedout. Characteristic mini-beam dose distributions were obtained with the developed collimator using a conventional X-ray source. With the exchangeable 3D-printed plates, FWHM and ctc from 0.52 to 2.11mm, and from 1.77 to 4.61mm were achieved, with uncertainties ranging from 0.01% to 8.98%, respectively. The FWHM and ctc obtained with the EBT-XD films are in agreement with the design of each mini-beam collimator configuration. For dose rates in the order of several Gy/min, the highest PVDR of 10.09 ± 1.08 was achieved with a collimator configuration of 0.5mm thick plastic plates and 2mm thick metal plates. Exchanging the tungsten plates with the lower-density metal brass reduced the PVDR by approximately 50%. Also, increasing the dose rate to ultra-high dose rates was feasible with the mini-beam collimator, where a PVDR of 24.26 ± 2.10 was achieved. Finally, it was possible to deliver and quantify mini-beam dose distribution patterns in vitro. With the developed collimator, we achieved various mini-beam dose distributions that can be adjusted according to the needs of the user in regards to FWHM, ctc, PVDR and SCD, while accounting for beam divergence. Therefore, the designed mini-beam collimator may enable low-cost and versatile pre-clinical research on mini-beamirradiation.

Growth Dynamics of Ultrathin Films of Benzo[1,2-b:4,5-b’]dithiophene Derivatives on Au(111): A Photoelectron Spectroscopy Investigation

Ultrathin films of a stereoisomeric mixture of benzo[1,2-b:4,5-b']dithiophene derivatives were grown by thermal evaporation in vacuum on Au(111), and they were studied in situ by photoelectron spectroscopy. X-ray photons from a non-monochromatic Mg Kα conventional X-ray source and UV photons from a He I discharge lamp equipped with a linear polarizer were used. He I photoemission results were compared with density functional theory (DFT) calculations: density of states (DOS) and 3D molecular orbital density distribution. Au 4f, C 1s, O 1s, and S 2p core-level components suggest a surface rearrangement as a function of film nominal thickness, with the variation of the molecular orientation, from flat-laying at the initial deposition to tilted toward the surface normal at coverages exceeding 2 nm. Eventually, the DFT results were exploited in assigning of the valence band experimental structures. Moreover, polarization-dependent photoemission confirmed the tilted arrangement of the molecules, starting at 2 nm. A variation of the work function of 1.4 eV with respect to the clean substrate was measured, together with a valence band offset of 1.3 eV between the organic layer and gold.

Virtual differential phase-contrast and dark-field imaging of x-ray absorption images via deep learning.

Weak absorption contrast in biological tissues has hindered x-ray computed tomography from accessing biological structures. Recently, grating-based imaging has emerged as a promising solution to biological low-contrast imaging, providing complementary and previously unavailable structural information of the specimen. Although it has been successfully applied to work with conventional x-ray sources, grating-based imaging is time-consuming and requires a sophisticated experimental setup. In this work, we demonstrate that a deep convolutional neural network trained with a generative adversarial network can directly convert x-ray absorption images into differential phase-contrast and dark-field images that are comparable to those obtained at both a synchrotron beamline and a laboratory facility. By smearing back all of the virtual projections, high-quality tomographic images of biological test specimens deliver the differential phase-contrast- and dark-field-like contrast and quantitative information, broadening the horizon of x-ray image contrast generation.

Optimization of the visibility of a tunable dual-phase x-ray grating interferometer

Dual-phase x-ray grating interferometry (DP-XGI) is a recently developed imaging technique that can retrieve structural information in the sub-micro scale over areas in the millimeter range. This is performed by use of the scattering signal, which is sensitive to structures that lie below the intrinsic spatial resolution of the imaging system. A quantitative understanding of the microstructure is possible when the scattering signal is retrieved within a range of auto-correlation lengths of the features of interest. High visibility of fringes in this length range is desirable, but no straightforward framework exists for choosing design parameters of the imaging system for such optimization. The purpose of this work is to present an optimization protocol for DP-XGI based on a Fresnel propagation simulation framework which evaluates different parameters of the optical system, utilizing the mean visibility of the fringes at the detector plane as a figure of merit to optimize the DP-XGI for a conventional lab x-ray source. The performance of the numerical simulation with realistic component parameters is validated with the experimental results obtained at a lab-based setup. The results of the validation confirm the robustness of the model for the evaluation of the different components of the interferometer and its optimization at low and high energies.

Visualization of temporomandibular joint articular cartilage using synchrotron-radiation X-ray phase-contrast imaging

X-ray phase-contrast imaging using synchrotron radiation was applied to visualize non-invasively the fine structures of articular cartilage of temporomandibular joint (TMJ). Among various X-ray phase-contrast imaging methods, we chose diffraction enhanced imaging (DEI) and carried out experiments using synchrotron radiation, aiming to visualize TMJ articular cartilage of rats and to identify the optimum X-ray energy. For comparison, the same sample was observed by a conventional laboratory X-ray source and X-ray micro-CT apparatus. DEI was able to visualize the articular cartilage of the mandibular condyle, which was not possible with the conventional laboratory X-ray source and X-ray micro-CT apparatus. DEI could also visualize the fibrous and proliferative layers in the articular cartilage of the mandibular condyle. We found that the optimum imaging energy was 20 keV for our sample. It was shown that DEI is a promising method for non-invasive visualization of TMJ articular cartilage. Our findings will open up new possibilities for applications of DEI with synchrotron radiation for basic medical and preclinical research.

Low-density foreign body detection in food products using single-shot grid-based dark-field X-ray imaging

This study presents a novel approach for detecting low-density foreign bodies (FBs) in food products using single-shot grid-based dark-field X-ray imaging (SG-DFXI). SG-DFXI obtains information related to the sample's small-angle X-ray scattering using a conventional X-ray source and grid. It is specifically utilized to detect low-density materials that are invisible when using conventional techniques. To demonstrate its efficacy, an experiment was conducted with food samples containing low-density FBs such as wood, Styrofoam, pencil lead, and soft plastic. A quantitative evaluation was conducted based on the contrast-to-noise ratio (CNR) and relative contrast gain (RCG). The proposed method detected low-density FBs barely visible in absorption images. Additionally, the CNR values measured in dark-field images were approximately 2.8–10.5 times larger than those in the absorption images, indicating that the proposed approach significantly improved the ability to detect low-density FBs in food samples. The RCG characteristic was improved as the system's autocorrelation length ( ξ G ) increased; the RCG value for ξ G = 453 nm was approximately 2.5 times larger than that for ξ G = 171 nm. • Method detecting low-density foreign bodies (FBs) in food products is proposed. • Single-shot grid-based dark-field X-ray imaging (SG-DFXI) method is used. • SG-DFXI obtains information related to samples' small-angle X-ray scattering. • The experiment used food samples with FBs like wood, Styrofoam, soft plastic, etc. • CNR and relative contrast gain (RCG) were used for quantitative evaluation.

X-ray Phase Contrast Imaging from Synchrotron to Conventional Sources: A Review of the Existing Techniques for Biological Applications

Since the seminal work of Roentgen, X-ray imaging mainly uses the same physical phenomenon: the absorption of light by matter. Thanks to third-generation synchrotrons that provide a high flux of quasi-coherent X-rays, we have seen in recent years new imaging concepts such as phase contrast or dark-field imaging that were later adapted to conventional X-ray sources. These innovative imaging techniques are particularly suitable for visualizing soft matter, such as biological tissues. After a brief introduction to the physical foundations of these two techniques, we present the different experimental set-ups that are now available to produce such contrasts: propagation, analyzer-based, grating interferometry and non-interferometric methods, such as coded aperture and modulation techniques. We present a comprehensive review of their principles; associated data processing; and finally, their requirements for their transfer outside of synchrotrons. In conclusion, gratings interferometry, coded aperture and modulation techniques seem to be the best candidates for the widespread use of phase contrast and dark-field imaging on low-cost X-ray sources.

Numerical evaluation of high-energy, laser-Compton x-ray sources for contrast enhancement and dose reduction in clinical imaging via gadolinium-based K-edge subtraction.

Conventional x-ray sources for medical imaging utilize bremsstrahlung radiation. These sources generate large bandwidth (BW) x-ray spectra with large fractions of photons that impart a dose, but do not contribute to image production. X-ray sources based on laser-Compton scattering can have inherently small energy BWs and can be tuned to low dose-imparting energies, allowing them to take advantage of atomic K-edge contrast enhancement. This paper investigates the use of gadolinium-based K-edge subtraction imaging in the context of mammography using a laser-Compton source through simulations quantifying contrast and dose in such imaging systems as a function of laser-Compton source parameters. Our simulations indicate that a K-edge subtraction image generated with a 0.5% BW (FWHM) laser-Compton x-ray source can obtain an equal contrast to a bremsstrahlung image with only 3% of the dose.

X-ray grating interferometry design for the 4D GRAPH-X system

The 4D GRAPH-X (Dynamic GRAting-based PHase contrast x-ray imaging) project aims at developing a prototype of an x-ray grating-based phase-contrast imaging scanner in a laboratory setting, which is based on the Moirè single-shot acquisition method in order to be optimized for analysing moving objects (in the specific case, a dynamic thorax phantom), that could evolve into a suitable tool for biomedical applications although it can be extended to other application fields. When designing an x-ray Talbot-Lau interferometer, high visibility and sensitivity are two important figures of merit, strictly related to the performance of the system in obtaining high quality phase contrast and dark-field images. Wave field simulations are performed to optimize the setup specifications and construct a high-resolution and high-sensitivity imaging system. In this work, the design of a dynamic imaging setup using a conventional milli-focus x-ray source is presented. Optimization by wave front simulations leads to a symmetric configuration with 5.25 μm pitch at third Talbot order and 45 keV design energy. The simulated visibility is about 22%. Results from GATE based Monte Carlo simulations show a 19% transmission percentage of the incoming beam into the detector after passing through all the gratings and the sample. Such results are promising in view of building a system optimized for dynamic imaging.

Fluence adaptation for contrast-based dose optimization in x-ray phase-contrast imaging.

X-ray phase-contrast imaging (XPCI) can provide multiple contrasts with great potentials for clinical and industrial applications, including conventional attenuation, phase contrast, and dark field. Grating-based imaging (GBI) and edge-illumination (EI) are two promising types of XPCI as the conventional x-ray sources can be directly utilized. For the GBI and EI systems, the phase-stepping acquisition with multiple exposures at a constant fluence is usually adopted in the literature.This work, however, attempts to challenge such a constant fluence concept during the phase-stepping process and proposes a fluence adaptation mechanism for dosereduction. Given the importance of patient radiation dose for clinical applications, numerous studies have tried to reduce patient dose in XPCI by altering imaging system designs, data acquisition, and information retrieval. Recently, analytic multiorder moment analysis has been proposed to improve the computing efficiency. In these algorithms, multiple contrasts can be calculated by summing together the weighted phase-stepping curves (PSCs) with some kernel functions, which suggests us that the raw data at different steps have different contributions for the noise in retrieved contrasts. Therefore, it is possible to improve the noise performance by adjusting the fluence distribution during the phase-stepping process directly. Based on analytic retrieval formulas and the Gaussian noise model for detected signals, we derived an optimal adaptive fluence distribution, which is proportional to the absolute weighting kernel functions and the root of original sample PSCs acquired under the constant fluence. Considering that the original sample PSC might be unavailable, we proposed two practical forms for the GBI and EI systems, which are also able to reduce the contrast noise when comparing with the constant fluence distribution. Since the kernel functions are target contrast-dependent, our proposed fluence adaptation mechanism provides a way of realizing a contrast-based dose optimization while keeping the same noiselevel. To validate our analyses, simulations and experiments are conducted for the GBI and EI systems. Simulated results demonstrate that the dose reduction ratio between our proposed fluence distributions and the typical constant one can be about 20% for the phase contrast, which is consistent with our theoretical predictions. Although the experimental noise reduction ratios are a little smaller than the theoretical ones, low-dose experiments observe better noise performance by our proposed method. Our simulated results also give out the effective ranges of the parameters of the PSCs, such as the visibility in the GBI, the standard deviation, and the mean value in the EI, providing a guidance for the use of our proposed approach inpractice. In this paper, we propose a fluence adaptation mechanism for contrast-based dose optimization in XPCI, which can be applied to the GBI and EI systems. Our proposed method explores a new direction for dose reduction, and may also be further extended to other types of XPCI systems and information retrievalalgorithms.

Self-Assembly of Angiotensin-Converting Enzyme Inhibitors Captopril and Lisinopril and Their Crystal Structures.

The peptide angiotensin-converting enzyme inhibitors captopril and lisinopril are unexpectedly shown to exhibit critical aggregation concentration (CAC) behavior through measurements of surface tension, electrical conductivity, and dye probe fluorescence. These three measurements provide similar values for the CAC, and there is also evidence from circular dichroism spectroscopy for a possible conformational change in the peptides at the same concentration. Cryogenic transmission electron microscopy indicates the formation of micelle-like aggregates above the CAC, which can thus be considered a critical micelle concentration, and the formation of aggregates with a hydrodynamic radius of ∼6–7 nm is also evidenced by dynamic light scattering. We also used synchrotron radiation X-ray diffraction to determine the single-crystal structure of captopril and lisinopril. Our results improve the accuracy of previous data reported in the literature, obtained using conventional X-ray sources. We also studied the structure of aqueous solutions containing captopril or lisinopril at high concentrations. The aggregation may be driven by intermolecular interactions between the proline moiety of captopril molecules or between the phenylalanine moiety of lisinopril molecules.

A type of X-ray diffractometer with adaptive X-ray spot sizes

In order to realize micron scale to millimeter scale phase structure analysis, as well as accurate phase structure analysis of surface uneven samples, X-ray diffractometer named Hawk-II, which can adaptively adjust the diameter of irradiated X-ray beam spot according to the diameter of internal tangential circle at the measured point, is developed by combining X-ray diffraction technology, CCD camera imaging technology and slightly-focusing ploycapillary X-ray control technology. The X-ray source system, six-dimensional linkage motion system, CCD camera, detection system and control system based on LabVIEW are the main components of the Hawk-II. Compared with the 3°–5° divergence of the conventional X-ray source, the divergence of the X-ray emitted by the slightly-focusing polycapillary X-ray optics is only about 0.15° and also the intensity within the beam spot range is dozens of times stronger. Therefore, the shift of peak position will not appear due to the pores, curvature or uneven surface of the sample, when Hawk-II is used to analyze the samples with irregular surface. The diffraction pattern of the uneven Ren Min Bi five-cent coin are collected in the Hawk-II and PANalytical X-Pert Pro MPD conventional X-ray diffractometer respectively. By comparing the analysis results, it is found that the diffraction peaks measured by the X-Pert Pro MPD are shifted seriously, with a maximum deviation angle of 0.52°. While the diffraction peaks detected by the Hawk-II are basically consistent with the data from the standard PDF card, which verifies the advantages of the analysis of irregular samples by the Hawk-II. In order to explore the difference between different beam spots used for analysis at the same point, red and green porcelain fired in Qing dynasty and GaAs-based Cu and Fe plated films are analyzed by the Hawk-II. It is found that when the samples are relatively uniform, the intensities of diffraction peaks of different beam spots are relatively close, while when the samples are not uniform, the diffraction peaks vary greatly. Especially, some microcrystalline phases can be detected only with large beam spots. In addition, to verify the adaptive functionality of the Hawk-II, a bronze from the Western Han Dynasty, with different rust spots on it, is tested. It is found that the Hawk-II can adjust the beam spot size according to the different corrosion points, making the irradiation area coincide with the area to be analysed and the phase structure detected more accurately. Therefore, the Hawk-II is a general purpose X-ray diffractometer, which has the analytical capability from micron scale to millimeter scale and the energy dispersive X-ray fluorescence analysis function. Moreover, it has the advantages of the accurate analysis of irregular samples, fast detection speed, simple operation, etc. Based on the above analysis, the Hawk-II will be widely used in different fields.

Design and Performance of a Full Functional Electrochemical Cell for Lab Scale in-Situ GI-XRD Instruments

In-situ XRD may support electrochemical measurements by delivering analytical information about electrochemical processes. Since structural changes at the electrode/electrolyte interface are of specific interest, measurements are done usually in small angle reflection mode geometry. The surface sensitive grazing incidence – XRD (GI-XRD) in-situ technique allows the detection of short-lived electrode reaction products or products sensitive to ambient atmosphere exposure. This method finds applications for quite a number of investigations of electrochemical processes including corrosion, film growth and deposition, reconstruction of superficial regions, ion insertion battery materials, etc. The common cell designs for lab scale XRD equipment use thin electrolyte layers to avoid unacceptable beam intensity loss through water. The use of synchrotron radiation would reduce this shortcoming to some extent but is much less accessible.In 1986, Fleischmann et al. presented an in-situ XRD thin layer cell in reflection as well as in transmission mode, where a X-ray transparent Mylar foil was used as window material [1]. However, this geometry restricts the positioning of counter and reference electrodes and therefore has unfavorable current density distribution, has very small electrolyte volume, is vulnerable to side reactions with gas evolution and does not allow high flow rates for the solution. Thus, the general applicability is limited.In our proposed in-situ cell design for GI-XRD, the electrochemical cell is fully functional, avoiding all of the above mentioned drawbacks [2]. The solution of this issue is the "backside-illumination" (or "inverse" illumination) of a thin film working electrode applied on a thin polymer foil as a support by the X-ray beam at a small incident angle. On the opposite side a conventional electrochemical cell with reference electrode and counter electrode and sufficient solution volume can be used. The big advantage of this design is that the X-ray only has to penetrate the foil and the thin layer of electrode material resulting in high signals from the region of interest. It is used with a conventional laboratory X-ray source and does not need high intensity synchrotron radiation. With this cell design, problems with bulk solution resistance, inhomogeneous current-density distribution, insufficient bath agitation or gas evolution as side reaction are eliminated.In this contribution, details of the cell design, analysis of current density distribution within the thin current collector and the electrochemical cell, results of calibration measurements and measurements on copper as an example for a galvanic deposition/dissolution process are presented.[1] M. Fleischmann, A. Oliver, and J. Robinson, ‘In Situ X-ray diffraction studies of electrode solution interfaces’, Electrochimica Acta, vol. 31, no. 8, pp. 899–906, (1986)[2] S. Reither, W. Artner, A. Eder, S. Larisegger, M. Nelhiebel, C. Eisenmenger-Sittner, G. Fafilek, ‘On the In-Situ Grazing Incidence X-Ray Diffraction of Electrochemically Formed Thin Films’, ECS Transactions, 80 (10) 1231-1238, (2017) 10.1149/08010.1231ecst Figure 1

Electron Density and Effective Atomic Number Measurement by Using a Newly Developing Photon Counting CT System

We developed the photon counting CT system by using a conventional laboratory X-ray source and a CdTe line sensor. Attenuation coefficients were obtained from the measured CT image data. Our suggested method for deriving the electron density and effective atomic number from the measured attenuation coefficients was tested experimentally. The accuracy of the electron densities and effective atomic numbers are about <5 % (the averages of absolute values are 2.6 % and 3.1 %, respectively) for material of 6< Z and Zeff <13. Our suggested simple method, in which we do not need the exact source X-ray spectrum and detector response function, achieves comparable accuracy to the previous reports.

Single spectrum three-material decomposition with grating-based x-ray phase-contrast CT

Grating-based x-ray phase-contrast imaging provides three simultaneous image channels originating from a single image acquisition. While the phase signal provides direct access to the electron density in tomography, there is additional information on sub-resolutional structural information which is called dark-field signal in analogy to optical microscopy. The additional availability of the conventional attenuation image qualifies the method for implementation into existing diagnostic routines. The simultaneous access to the attenuation coefficient and the electron density allows for quantitative two-material discrimination as demonstrated lately for measurements at a quasi-monochromatic compact synchrotron source. Here, we investigate the transfer of the method to conventional polychromatic x-ray sources and the additional inclusion of the dark-field signal for three-material decomposition. We evaluate the future potential of grating-based x-ray phase-contrast CT for quantitative three-material discrimination for the specific case of early stroke diagnosis at conventional polychromatic x-ray sources. Compared to conventional CT, the method has the potential to discriminate coagulated blood directly from contrast agent extravasation within a single CT acquisition. Additionally, the dark-field information allows for the clear identification of hydroxyapatite clusters due to their micro-structure despite a similar attenuation as the applied contrast agent. This information on materials with sub-resolutional microstructures is considered to comprise advantages relevant for various pathologies.

Simulations of single-shot X-ray phase-contrast tomography based on edge illumination

Single-shot X-ray phase-contrast imaging can simplify acquisition processes and reduce the dose delivered to a patient, and also reduce the imaging time, which increases the usability of the system for computed tomography (CT) and dynamic planar imaging. Edge illumination (EI) is a promising method of X-ray phase-contrast imaging that is expected to be implemented in compact devices using conventional X-ray sources. EI-based single-shot X-ray phase-contrast tomography (XPCT) has attracted much attention in recent years. Although single-shot XPCT is possible, further studies are needed before this method is translated into real-world applications. In this paper, a simulation model was built to study EI-baesd single-shot XPCT, including the main hardware conditions (such as the source, mask, detector, objects, and geometric conditions) and some key factors (such as photon statistics, X-ray spectrum, pixel crosstalk, and X-ray absorption). The extraction of information and reconstruction in the absorption, phase, and differential phase signals were implemented, and the effects of pixel crosstalk, photon statistics, and mask thickness on the imaging results were studied. The results suggest that XPCT has significant potential for improving imaging quality and reducing the radiation dose compared to traditional absorption-based CT techniques. The effects of pixel crosstalk are negligible when σc, the standard deviation of the Gaussian function, is much smaller than the detector pixel as a considerable top width remains in the pixel point spread function. Besides, a mask of considerable thickness is required to ensure the reconstruction accuracy of the quantitative information.