Direct X-ray Research Articles

XCT and DLW: Synergies of Two Techniques at Sub-Micrometer Resolution

Direct Laser Writing (DLW) and X-ray computed tomography (XCT) both offer unique possibilities in their respective fields. DLW produces full three-dimensional (3D) polymer structures on the microscale with resolutions below 100 nm. The fabricated structures can be analysed by XCT or X-ray microscopy (XRM), which incorporates additional X-ray lenses, in three dimensions down to a minimal basic spatial resolution of about 500 nm or 50 nm, respectively. In this work, two different DLW structures are analysed via XCT. Internal defects are detected and analysed for the purpose of quality control. Defects and structures with sizes down to 1.5 µm are successfully analysed. A 3D reconstruction and internal, hidden features of the fabricated structures are shown and discussed. In a first-of-its-kind study, we demonstrate the detectability of a single-voxel line inside a fabricated structure that would not be detectable with SEM or light microscopy. Furthermore, the direct fabrication on a PET substrate is shown to overcome the high X-ray absorbance of commonly used glass substrates. Attenuation spectra of SZ2080 and glass substrates are compared to a fabrication route direct on a 170 µm PET foil. The practical aspects of XCT measurements for DLW structures on different substrates will be discussed.

A review on BiI3 perovskites and composites for direct X-ray detection

Bismuth-triiodide has received remarkable attention because of its properties like low toxicity, wide band gap, high density, high attenuation coefficient, and defect tolerance for direct X-ray detection applications. The material has demonstrated promising X-ray detection results in polycrystalline films and single-crystal detectors. However, the inherent defects and voids in the structure of BiI 3 create recombination centers and decrease the charge collection in the detector. Over the last few years, BiI 3 -polymer composites and BiI 3 -based perovskites have been investigated for the defect tolerance to deliver high sensitivity, high SNR, and low detection limit. These composites and perovskites tailor the trap density in the BiI 3 and increase the density of shallow defects, which helps to improve the charge collection. In this review, we summarize the properties and limitations of BiI 3 and the role of deep and shallow defects in charge carriers’ transportation. The highlights of the recent developments in BiI 3 -based composites and perovskites to address these challenges to yield high material performance for direct X-ray detection applications.

Can American Orthopaedic Foot and Ankle Society (AOFAS) score prevent unnecessary MRI in isolated ankle ligament injuries?

Ankle injuries are the most common musculoskeletal injuries. Its incidence is also high among sports injuries. Direct X-ray, ultrasound and MRI can be requested after the history and physical examination in the patient who presents with ankle ligament injury. Some classifications are used for requesting direct X-ray after ankle injury. Since clear limits are not specified in the literature for MRI, the rate of unnecessary MRI examinations is high. We argue that the decision can be made according to the AOFAS score to be checked before MR is requested, and thus unnecessary MR requests can be reduced. Ankle MRI images of patients who underwent ankle MRI due to ankle trauma between January 2018 and December 2020 were scanned. 328 patients who met the criteria were included in the study. Patients with AOFAS scores in their outpatient clinic records were identified. AOFAS scores of patients with at least one ligament injury and those with normal MR images were statistically compared. Sensitivity and specificity were determined for the AOFAS score using ROC analysis. Patients with ligament damage as a result of MRI examination were 21.3% (n=70), and patients without any ligament damage were 78.7% (n=258). There was a statistically significant difference in terms of AOFAS between the group with ligament damage and the group without ligament damage (p< 0.05). In the ROC analysis, the AOFAS threshold value for MR request was determined as 80.5 (84.3% sensitivity and 72.3% specificity). Based on the determined threshold value, 73 patients who had unnecessary MRI would have been eliminated, thus reducing the number of MRIs by 42.6%. The AOFAS scores of patients with ligament damage were statistically significantly lower than those of patients without ligament pathology. Unnecessary MRI can be significantly prevented by using the AOFAS score in ankle traumas without bone fractures.

Laparoscopic transperitoneal ureterolithotomy is an effective and safe method for >15 mm impacted ureteral stones in elderly patients: single center 10-year experience.

The aim of our study is to investigate the efficacy and safety of laparoscopic ureterolithotomy operation in elderly patients with large and impacted ureteral stones. Between January 2011 and July 2021, 66 elderly patients with impacted, > 15 mm upper and middle ureteral stones underwent laparoscopic ureterolithotomy in our center. The data for all patients were evaluated retrospectively. The mean age of the patients was 65 ± 5.43 years. The mean stone size was 20.2 ± 2.5 mm. The mean operation time was 93.6 ± 13.2 minutes. Among patients, 16 (24.2%) had history of unsuccessful shock wave lithotripsy and 12 (18.1%) patients had history of ureterorenoscopy. Stone-free rate was 95.4% in all patients. Modified Clavien grade 1 complications were seen in 18 patients (27.2%), but no significant perioperative and postoperative complications were observed. Urinary extravasation lasting 5, 7 and 9 days was observed in 5 patients (7.5%) who were treated conservatively. The mean hospital stay was 3.4 ± 1.52 days. The patients were asymptomatic at the 6th week post-op follow-up, and no stones were seen on direct X-ray and abdominal ultrasonography. Intravenous urography and non-contrast tomography (NCCT) taken 3 months later did not show any obstruction or stenosis in the ureter. Laparoscopic ureterolithotomy can be considered as the first treatment option for elderly patients with impacted and large ureteral stones, thanks to its high success and acceptable complication rates.

Direct X-Ray Detection of the Spin Hall Effect in CuBi

The spin Hall effect and its inverse are important spin-charge conversion mechanisms. The direct spin Hall effect induces a surface spin accumulation from a transverse charge current due to spin orbit coupling even in non-magnetic conductors. However, most detection schemes involve additional interfaces, leading to large scattering in reported data. Here we perform interface free x-ray spectroscopy measurements at the Cu L_{3,2} absorption edges of highly Bi-doped Cu (Cu_{95}Bi_{5}). The detected X-ray magnetic circular dichroism (XMCD) signal corresponds to an induced magnetic moment of (2.7 +/- 0.5) x 10-12 {\mu}_{B} A^{-1} cm^{2} per Cu atom averaged over the probing depth, which is of the same order as for Pt measured by magneto-optics. The results highlight the importance of interface free measurements to assess material parameters and the potential of CuBi for spin-charge conversion applications.

Comparative Analysis of Multilayer Lead Oxide-Based X-ray Detector Prototypes.

Lead oxide (PbO) photoconductors are proposed as X-ray-to-charge transducers for the next generation of direct conversion digital X-ray detectors. Optimized PbO-based detectors have potential for utilization in high-energy and dynamic applications of medical X-ray imaging. Two polymorphs of PbO have been considered so far for imaging applications: polycrystalline lead oxide (poly-PbO) and amorphous lead oxide (a-PbO). Here, we provide the comparative analysis of two PbO-based single-pixel X-ray detector prototypes: one prototype employs only a layer of a-PbO as the photoconductor while the other has a combination of a-PbO and poly-PbO, forming a photoconductive bilayer structure of the same overall thickness as in the first prototype. We characterize the performance of these prototypes in terms of electron–hole creation energy (W±) and signal lag—major properties that define a material’s suitability for low-dose real-time imaging. The results demonstrate that both X-ray photoconductive structures have an adequate temporal response suitable for real-time X-ray imaging, combined with high intrinsic sensitivity. These results are discussed in the context of structural and morphological properties of PbO to better understand the preparation–fabrication–property relationships of this material.

Direct Conversion X-ray Detector with Micron-Scale Pixel Pitch for Edge-Illumination and Propagation-Based X-ray Phase-Contrast Imaging.

In this work, we investigate the potential of employing a direct conversion integration mode X-ray detector with micron-scale pixels in two different X-ray phase-contrast imaging (XPCi) configurations, propagation-based (PB) and edge illumination (EI). Both PB-XPCi and EI-XPCi implementations are evaluated through a wave optics model—numerically simulated in MATLAB—and are compared based on their contrast, edge-enhancement, visibility, and dose efficiency characteristics. The EI-XPCi configuration, in general, demonstrates higher performance compared to PB-XPCi, considering a setup with the same X-ray source and detector. However, absorption masks quality (thickness of X-ray absorption material) and environmental vibration effect are two potential challenges for EI-XPCi employing a detector with micron-scale pixels. Simulation results confirm that the behavior of an EI-XPCi system employing a high-resolution detector is susceptible to its absorption masks thickness and misalignment. This work demonstrates the potential and feasibility of employing a high-resolution direct conversion detector for phase-contrast imaging applications where higher dose efficiency, higher contrast images, and a more compact imaging system are of interest.

Dark Current Modeling for a Polyimide-Amorphous Lead Oxide-Based Direct Conversion X-ray Detector.

The reduction of the dark current (DC) to a tolerable level in amorphous selenium (a-Se) X-ray photoconductors was one of the key factors that led to the successful commercialization of a-Se-based direct conversion flat panel X-ray imagers (FPXIs) and their widespread clinical use. Here, we discuss the origin of DC in another X-ray photoconductive structure that utilizes amorphous lead oxide (a-PbO) as an X-ray-to-charge transducer and polyimide (PI) as a blocking layer. The transient DC in a PI/a-PbO detector is measured at different applied electric fields (5–20 V/μm). The experimental results are used to develop a theoretical model describing the electric field-dependent transient behavior of DC. The results of the DC kinetics modeling show that the DC, shortly after the bias application, is primarily controlled by the injection of holes from the positively biased electrode and gradually decays with time to a steady-state value. DC decays by the overarching mechanism of an electric field redistribution, caused by the accumulation of trapped holes in deep localized states within the bulk of PI. Thermal generation and subsequent multiple-trapping (MT) controlled transport of holes within the a-PbO layer governs the steady-state value at all the applied fields investigated here, except for the largest applied field of 20 V/μm. This suggests that a thicker layer of PI would be more optimal to suppress DC in the PI/a-PbO detector presented here. The model can be used to find an approximate optimal thickness of PI for future iterations of PI/a-PbO detectors without the need for time and labor-intensive experimental trial and error. In addition, we show that accounting for the field-induced charge carrier release from traps, enhanced by charge hopping transitions between the traps, yields an excellent fit between the experimental and simulated results, thus, clarifying the dynamic process of reaching a steady-state occupancy level of the deep localized states in the PI. Practically, the electric field redistribution causes the internal field to increase in magnitude in the a-PbO layer, thus improving charge collection efficiency and temporal performance over time, as confirmed by experimental results. The electric field redistribution can be implemented as a warm-up time for a-PbO-based detectors.

Modes of Occurrence of Critical Metal Elements (Li, REEs and Other Critical Elements) in Low-Grade Bauxite from Southern Shanxi Province, China

The low-grade bauxite in southern Shanxi Province, China is enriched in multiple critical metal elements, including Li, Ga, V, Se, and rare earth elements (REEs), which have reached the standard of comprehensive utilization as independent deposits or associated resources. Even more importantly, identifying the modes of occurrence of these critical elements is essential for designing technologies to extract critical metals from bauxite ores. This study used a combination of direct (X-ray diffraction, scanning electron microscopy–energy dispersive X-ray spectroscopy, and micro-X-ray fluorescence spectrometer), and indirect (size sieving method, float-sink experiment, and correlation analysis) methods to effectively reveal the distribution of critical elements in the different identified mineral phases. The results regarding the low-grade bauxite are as follows: Li was mainly hosted in cookeite as an independent mineral; Ga was mainly associated with diaspore; anatase is the main carrier mineral for V; REEs were present in the low-grade bauxite in multiples modes of occurrence, the most common of which were goyazite, and to a lesser extent, florencite; Se primarily occurs in sulfides. This study contributes to the development and utilization of these essential metal resources in bauxite by providing a useful reference.

The eROSITA view of the Abell 3391/95 field: Case study from the Magneticum cosmological simulation

Context.Clusters of galaxies reside at the nodes of the cosmic web, interconnected by filamentary structures that contain tenuous diffuse gas, especially in the warm-hot phase. Galaxy clusters grow by mergers of smaller objects and gas that are mainly accreted through these large-scale filaments. For the first time, the large-scale cosmic structure and a long gas-emission filament have been captured by eROSITA on board the Spectrum-Roentgen-Gamma mission in a direct X-ray observation of the A3391/95 field.Aims.We investigate the assembly history of an A3391/95-like system of clusters and the thermo-chemical properties of the diffuse gas in it by connecting simulation predictions to the eROSITA observations with the aim to constrain the origin and nature of the gas in the pair-interconnecting bridge.Methods.We analysed the properties of a system resembling A3391/95, extracted from the (352h−1cMpc)3volume of the Magneticum Pathfinder cosmological simulations atz= 0.07. We tracked the main progenitors of the pair clusters and of surrounding groups back in time to study the assembly history of the system and its evolution.Results.Similarly to the observed A3391/95 system, the simulated cluster pair is embedded in a complex network of gas filaments, with structures aligned over more than 20 projected Mpc, and the whole region collapses towards the central overdense node. The spheres of influence (3 ×R200) of the two main clusters already overlap atz= 0.07, but their virial boundaries are still physically separated. The diffuse gas located in the interconnecting bridge closely reflects the warm-hot intergalactic medium, with a typical temperature of ~1 keV and an overdensityδ ~100 with respect to the mean baryon density of the Universe, and a lower enrichment level compared to the intra-cluster medium in clusters. We find that most of the bridge gas collapsed from directions roughly orthogonal to the intra-cluster gas accretion directions, and its origin is mostly unrelated to the two cluster progenitors. We find clear signatures in the surrounding groups of infall motion towards the pair, such as significant radial velocities and a slowdown of gas compared to dark matter. These findings further support the hypothesis that the Northern Clump (MCXC J0621.7-5242) cluster infalls along a cosmic gas filament towards Abell 3391 and might be merging with it.Conclusions.We conclude that in this configuration, the pair clusters of the A3391/95-like system are in a pre-merger phase and have not yet interacted. The diffuse gas in the interconnecting bridge is mostly warm filament gas and not tidally stripped cluster gas.

Polymer-BiI3 composites for high-performance, room-temperature, direct X-ray detectors.

Low-energy X-rays have a predominant role in medical diagnostic applications, grown tremendously during recent Covid-19 pandemic times. Synthesis of stable, PMMA/polystyrene-BiI3 composites has been done through a facile, low-cost, dry-tumble mixing technique for direct X-ray detector applications. Comparative analysis of structural, optical, and photocurrent responses upon irradiation with low-energy X-rays (30 and 60 kV) ensue that PS-BiI3 demonstrates high SNR 3300, sensitivity 189 µC Gy−1 cm−3 and fast response time 30 ms, at dose rate 1.68 mGy s−1, affirming the composite to be prospective candidate for low-energy, room-temperature, direct X-ray detectors under low bias conditions.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1557/s43579-022-00185-6.

Sensitive direct x-ray detectors based on the In–Ga–Zn–O/perovskite heterojunction phototransistor

Direct x-ray detectors are essential in many applications including medical tomography, security inspection, nondestructive testing, crystallography and astronomy. Despite the rapid advances in recent years, the currently available direct x-ray detectors are still limited by the insufficient photon-to-charge conversion, compromising the detection sensitivity, ease of fabrication, cost and flexibility. Here we demonstrate a device concept of heterojunction phototransistor with high internal-gain effect to realize the sensitive x-ray direct detection. Specifically, the heterojunction phototransistors are mainly composed of an industrially available In–Ga–Zn–O channel and all-inorganic perovskite nanocrystals used as x-ray photoconductor. In contrast to the conventional diode-based x-ray detectors, phototransistor allows both electrical gating and photodoping effect for efficient carrier density modulation, leading to the low dark-current and high photoconductive gain. The introduction of such high-gain mechanism into x-ray detectors can offer internal signal amplification for photogenerated currents without the increment of noise, thereby leading to the high sensitivity over 106 μC Gyair −1 cm−2 and detection limit down to 3 μGyair s−1. These results suggest that the heterojunction x-ray phototransistor can provide the most promising platform to achieve high-performance direct x-ray detectors with both high sensitivity, light weight, flexibility and low cost.

Quasi-2D Perovskite Crystalline Layers for Printable Direct Conversion X-Ray Imaging.

Polycrystalline perovskite film-based X-ray detector is an appealing technology for assembling large scale imager by printing methods. However, thick crystalline layer without trap and solvent residual is challenging to fabricate. Here, the authors report a solution method to produce high quality quasi-2D perovskite crystalline layers and detectors that are suitable for X-ray imaging. By introducing n-butylamine iodide into methylammonium lead iodide precursor and coating at elevated temperatures, compact and crystalline layers with exceptional uniformity are obtained on both rigid and flexible substrates. Photodiodes built with the quasi-2D layers exhibit a low dark current and stable operation under constant electrical field over 96 h in dark, and over 15 h under X-ray irradiation. The detector responds sensitively under X-ray, delivering a high sensitivity of 1214µCGyair -1 cm-2 and a sensitivity gain is observed when operated under higher fields. Finally, high resolution images are demonstrated using a single pixel device that can resolve 80-200µm features. This work paves the path for printable direct conversion X-ray imager development.

X-ray protective materials from barium sulfate/amorphous cellulose/natural rubber composites

In this study, barium sulfate/amorphous cellulose (Ba/AC) was incorporated into natural rubber to produce X-ray shielding materials. Ba/AC was prepared by in-situ regeneration of amorphous cellulose from eucalyptus pulp and office waste paper with barium chloride. The shielding sheets were prepared by mixing vulcanized natural rubber with Ba/AC using both office waste paper (NR-W) and purified eucalyptus pulp (NR-E) and were compared to barium sulfate powder (NR-P) used as a conventional material. NR-W and NR-E exhibited a predominant attenuation property compared to that of NR-P. The amorphous cellulose surrounded by barium sulfate is essential in distributing and reducing the aggregation of barium sulfate particles. This behavior results in most incident X-ray beams being effectively absorbed. Subsequently, prototypes were fabricated using NR-W and NR-E with a thickness of 0.25-mm Pb in accordance with the quality standards of medical diagnostic X-ray machines in Thailand. The head, thyroid, and breast shields were produced to protect from direct X-ray beams. Additionally, a lab coat was prepared to block scattered beams. Finally, the fabricated X-ray shielding prototypes are eco-friendly, cost-effective, and nontoxic.

Functional dynamics of G-protein-coupled receptor shown by femtosecond X-ray scattering

The development of ultrafast X-ray free-electron lasers (XFELs) gives a new avenue to experimentally investigate protein dynamics in the picosecond and femtosecond time regimes. For G-protein-coupled receptors (GPCRs) like rhodopsin, an important question is how the rapid local dynamics of the ligand initiate the functional protein transitions. However, structural evidence is lacking because until now the extreme reaction speed has precluded direct X-ray diffraction approaches. Here we show how solution X-ray scattering combined with molecular simulations informs the functional dynamics of membrane proteins in ways that could previously only be imagined.

Direct x-ray detection using thin-film pentacene Schottky diodes

Direct x-ray detectors using thermally evaporated pentacene thin-films are fabricated in Schottky and coplanar configurations and are analysed for low x-ray dose rates. In both configurations, the x-ray induced photocurrent is found to be five orders of magnitude greater than the theoretically evaluated threshold value that may reflect possible internal gain mechanism. Coplanar detectors showed unstable x-ray photocurrent characteristics; on the other hand, Schottky photodiode structure showed stable response and thus allowed to proceed for x-ray sensitivity measurements. Pentacene-based Schottky detector presented a decent volume sensitivity of 162.3 μC/mGy/cm3. The high x-ray sensitivity of pentacene Schottky detector can be due to the complete depletion of the thin-film at the operating reverse bias, revealed by transfer characteristics of fabricated pentacene MESFET. Such a reasonably good x-ray photoconversion in low-Z organic semiconducting materials uncovers the possibility of implementing them in x-ray medical dosimetry applications and in wearable electronic technology.

Остеотомія за Weil при хірургічному лікуванні метатарзалгії

Проаналізовані результати хірургічного лікування 9 пацієнтів (17 плеснофалангових суглобів) із застосуванням остеотомії за Weil. В усіх випадках було діагностовано метатарзалгію та відсутність плеснової параболи за прямою рентгенограмою. Результати оцінювали за схемою AOFAS та візуальною аналоговою шкалою в строки 6–27 місяців (у середньому 18,4 ± 4,5 місяця). Значимість різниці між середніми оцінена за допомогою двовибіркового t-тесту (α = 0,05). Функція стопи до та після операції становила 50,3 ± 5,7/82,8 ± 2,9 бала (p < 0,001), рівень болю — 6,5 ± 0,4/1,3 ± 0,1 см (p < 0,001). Остеотомія за Weil є ефективною хірургічною операцією, що сприяє суттєвому зменшенню больового синдрому та покращенню функції стопи.

Direct conversion X-ray detectors with 70 pA cm−2 dark currents coated from an alcohol-based perovskite ink

A poly(methyl methacrylate) blocking layer was found to reduce the dark current density in CH3NH3PbI3-based direct-conversion X-ray detectors to as low as 70 pA cm−2.

Photon-Counting Detector CT: Key Points Radiologists Should Know.

Photon-counting detector (PCD) CT is a new CT technology utilizing a direct conversion X-ray detector, where incident X-ray photon energies are directly recorded as electronical signals. The design of the photon-counting detector itself facilitates improvements in spatial resolution (via smaller detector pixel design) and iodine signal (via count weighting) while still permitting multi-energy imaging. PCD-CT can eliminate electronic noise and reduce artifacts due to the use of energy thresholds. Improved dose efficiency is important for low dose CT and pediatric imaging. The ultra-high spatial resolution of PCD-CT design permits lower dose scanning for all body regions and is particularly helpful in identifying important imaging findings in thoracic and musculoskeletal CT. Improved iodine signal may be helpful for low contrast tasks in abdominal imaging. Virtual monoenergetic images and material classification will assist with numerous diagnostic tasks in abdominal, musculoskeletal, and cardiovascular imaging. Dual-source PCD-CT permits multi-energy CT images of the heart and coronary arteries at high temporal resolution. In this special review article, we review the clinical benefits of this technology across a wide variety of radiological subspecialties.

Direct Conversion X-Ray Detectors with High Sensitivity at Low Dose Rate Based on All-Inorganic Lead-Free Perovskite Wafers

Direct Conversion X-Ray Detectors with High Sensitivity at Low Dose Rate Based on All-Inorganic Lead-Free Perovskite Wafers