X-ray Attenuation Coefficients Research Articles

Ion Leakage Current Control for Polycrystalline Metal Halide Perovskite Direct X-ray Detectors.

Metal halide perovskites have emerged as promising materials for X-ray detection due to their high X-ray attenuation coefficients, defect tolerance, and suitability for large-area, low-temperature fabrication. However, the intrinsic high ion conductivity of these materials presents challenges, such as high dark current density and current drift, which impair the stability and sensitivity of perovskite X-ray detectors. This study introduces an approach to mitigating these issues by incorporating 2,2,3,3,3-pentafluoropropylamine hydrochloride (PFH) into polycrystalline MAPbI3-xClx films using a one-step blade-coating method. PFH aggregates at grain boundaries, raising local vacuum energy levels and passivating surface defects, thereby reducing ion conductivity without affecting electron conductivity. As a result, this approach significantly reduces the dark current and enhances sensitivity, achieving a low detection limit of 14.7 nGyair/s. Additionally, it improves signal stability, consistency, and response speed of the detector. These findings suggest that PFH is a promising additive for advancing the performance and practical application of polycrystalline metal halide perovskite-based X-ray detectors.

Multiphase distribution in partly saturated hierarchical nonwoven fibre networks under applied load using X-ray computed tomography

In many industrial applications, nonwoven fibre networks are facilitated to operate under partly saturated conditions, allowing for filtration, liquid absorption and liquid transport. Resolving the governing liquid distribution in loaded polyamide-6 (PA6) fibre networks using X-ray computed micro-tomography is a challenge due to the similar X-ray attenuation coefficients of water and PA6 and limitations in using background subtraction techniques if the network is deformed, which will be the case if subjected to compression. In this work, we developed a method using a potassium iodide solution in water to enhance the liquid’s attenuation coefficient without modifying the water’s rheological properties. Therefore, we studied the evolving liquid distribution in loaded and partly saturated PA6 fibre networks on the microscale. Increasing the external load applied to the network, we observed an exponential decrease in air content while the liquid content was constant, increasing the overall saturation with increasing network strain. Furthermore, the microstructural properties created by the punch-needle process in the manufacturing of the network significantly influenced the out-of-plane liquid distribution. The method has been proven helpful in understanding the results of adaptions in both the fibre network design and manufacturing process, allowing for investigating the resulting liquid distribution on a microscale.

Gram-Scale Synthesis of Renal-Clearable Tantalum Nanodots with High Water Solubility for Computed Tomography Imaging In Vivo.

Tantalum (Ta) emerges as a promising element for advanced computed tomography (CT) imaging probes owing to its high X-ray attenuation coefficient and excellent biocompatibility. Nevertheless, the synthesis of renally clear Ta-based imaging probes through simple methods remains a significant challenge. Herein, we introduce a simple and gram-scale approach for the synthesis of renal-clearable Ta nanodots with high water solubility for CT imaging in vivo. The Ta nanodots, coordination polymers, are fabricated via coordination reactions involving Ta(OH)5, citric acid (CA), and hydrogen peroxide. The Ta nanodots exhibit an ultrasmall hydrodynamic diameter (2.8 nm), high water solubility (1.88 g/mL, 688 mg Ta/mL), superior X-ray absorption capacity, gram-scale production capability (>10 g in lab synthesis), renal-clearable ability, and good biocompatibility. The Ta nanodots possess superior CT imaging efficacy across diverse tube voltages, enabling highly sensitive gastrointestinal CT imaging, renal CT imaging, and CT angiography (CTA). Moreover, Ta nanodots maintain robust CT imaging capabilities even at high X-ray energies, and Ta nanodots-based spectral CT achieves metallic artifacts-minimized CTA. The proposed Ta nanodots present substantial potential as a potent CT imaging probe for diagnosing various diseases.

Computed Tomography Imaging Guided Microenvironment-Responsive Ir@WO3-x Dual-Catalytic Nanoreactor for Selective Radiosensitization.

Radiotherapy (RT) is often administered, either alone or in combination with other therapies, for most malignancies. However, the degree of tumor oxygenation, damage to adjacent healthy tissues, and inaccurate guidance remain issues that result in discontinuation or failure of RT. Here, a multifunctional therapeutic platform based on Ir@WO3-x is developed which simultaneously addresses these critical issues above for precision radiosensitization. Ir@WO3-x nanoreactors exhibit strong absorption of X-ray, acting as radiosensitizers. Moreover, ultrasmall Ir enzyme-mimic nanocrystals (NCs) are decorated onto the surface of the nanoreactor, where NCs have catalyst-like activity and are sensitive to H2O2 in the tumor microenvironment (TME) under near infrared-II (NIR-II) light stimulation. They efficiently catalyze the conversion of H2O2 to O2, thereby ameliorating hypoxia, inhibiting the expression of HIF-1α, and enhancing RT-induced DNA damage in cancerous tissue, further improving the efficiency of RT. Additionally, in response to high H2O2 levels in TME, the Ir@WO3-x nanoreactor also exerts peroxidase-like activity, boosting exogenous ROS, which increases oxidative damage and enhances ROS-dependent death signaling. Furthermore, Ir@WO3-x can serve as a high-quality computed tomography contrast agent due to its high X-ray attenuation coefficient and generation of pronounced tumor-tissue contrast. This report highlights the potential of advanced health materials to enhance precision therapeutic modalities.

Thermal insulation and X-ray attenuation properties of fired clay-perlite composites

In this work, the expanded perlite (EP) was used as an additive in local Hang Dong (HDC) and San Kham Phang (SPC) clays from Chiang Mai province, Thailand, for wall tile manufacturing and its influence on various properties were investigated. All samples were fabricated by drying and sintering the mixtures at 1100 °C for 8 h. Fired bulk density, shrinkage, water absorption and modulus of rupture were measured. With increasing perlite content, the density showed a decreasing trend (2.16–1.62 g/cm3 for HDC clay and 2.13 to 1.37 g/cm3 for SPC clay) with the corresponding reduction in the modulus of rupture. Both types of clays showed higher water absorbability when more perlite was added, indicating the hygroscopic properties of porous perlite particles. Phase and chemical composition indicated the uniform distribution of pea-pod-like perlite structure in clay matrix with strong interfacial bonding due to chemical reaction between perlite additive and clay matrix. X-ray attenuation coefficient was found to decrease in correspondence with the decreasing trend in density values. The thermal conductivity of perlite-added Hang Dong clay exhibited at least 10 times reduction compared to pure clay, suggesting the excellent insulation behavior. The HDC with 100 and 200 cm3 perlite showed good performance in terms of rupture strength, water absorbability, X-ray attenuation with additional insulation properties. Based on this perlite-clay composite study, the sample could be further optimized for its X-ray shielding application by infiltration with elemental or alloy particles.

Halide perovskite x-ray detectors: Fundamentals, progress, and outlook

Halide perovskites have demonstrated great potential in x-ray detectors, due to their high x-ray attenuation coefficient, large bulk resistance, ultralong carrier diffusion length, and adjustable bandgap. Moreover, their abundant raw materials and simple processing combined with excellent compatibility with integrated circuits make them ideal for cost-efficient and high-efficiency real-world imaging applications. Herein, we comprehensively reviewed advances and progress in x-ray detection devices based on halide perovskites. We expound on the fundamental mechanisms of interactions between x rays and matter as background and indicate different parameters for different types of x-ray detectors, which guides the basic requirements on how to select and design suitable materials for active layers. After emphasizing the superb properties of halide perovskites through the shortcomings of commercial materials, we evaluate the latest advancements and ongoing progress in halide perovskites with different dimensions and structures for both direct and indirect x-ray detectors, and discuss the effect of dimensional varieties on the device performance. We also highlight current challenges in the area of perovskite x-ray detectors and propose corresponding solutions to optimize halide perovskites and optimize x-ray detectors for next-generation imaging applications.

Cu2WS4-PEG Nanozyme as Multifunctional Sensitizers for Enhancing Immuno-Radiotherapy by Inducing Ferroptosis.

Unavoidable damage to normal tissues and tumor microenvironment (TME) resistance make it challenging to eradicate breast carcinoma through radiotherapy. Therefore, it is urgent to develop radiotherapy sensitizers that can effectively reduce radiation doses and reverse the suppressive TME. Here, a novel biomimetic PEGylated Cu2WS4 nanozyme (CWP) with multiple enzymatic activities is synthesized by the sacrificing template method to have physical radiosensitization and biocatalyzer-responsive effects on the TME. Experiment results show that CWP can improve the damage efficiency of radiotherapy on breast cancer cell 4T1 through its large X-ray attenuation coefficient of tungsten and nucleus-penetrating capacity. CWP also exhibit strong Fenton-like reactions that produced abundant ROS and GSH oxidase-like activity decreasing GSH. This destruction of redox balance further promotes the effectiveness of radiotherapy. Transcriptome sequencing reveals that CWP induced ferroptosis by regulating the KEAP1/NRF2/HMOX1/GPX4 molecules. Therefore, owing to its multiple enzymatic activities, high-atomic W elements, nucleus-penetrating, and ferroptosis-inducing capacities, CWP effectively improves the efficiency of radiotherapy for breast carcinoma in vitro and in vivo. Furthermore, CWP-mediated radiosensitization can trigger immunogenic cell death (ICD) to improve the anti-PD-L1 treatments to inhibit the growth of primary and distant tumors effectively. These results indicate that CWP is a multifunctional nano-sensitizers for radiotherapy and immunotherapy.

Optical and scintillation properties of hybrid manganese(II) bromides with formamidinium and acetamidinium cations.

In recent years, hybrid manganese(II) halides (HMHs) have attracted wide attention due to their impressive optical properties, low toxicity, and facile synthetic processibility. Being effective reabsorption-free phosphors, these compounds demonstrate the potential to be used as low-cost solution-processable scintillators. However, most of the HMHs studied to date contain bulk organic cations and, as a result, are characterized by low density and low X-ray stopping power. For this reason, we studied manganese(II) bromides with compact organic cations such as formamidinium (FA+) and acetamidinium (AcA+). In particular, we synthesized four new phases, two of which are characterized by octahedral coordination of manganese ions ((FA)MnBr3 and (AcA)MnBr3) and red emission, whereas the other two have tetrahedrally coordinated Mn2+ ions ((FA)3MnBr5 and (AcA)2MnBr4) and green emission. Photoluminescence (PL) and radioluminescence measurements demonstrated high PL quantum yields and reasonable scintillation light yields of acetamidinium-based compounds. In addition, unlike most known HMH-based scintillators, the discovered materials have a relatively high density due to the small fraction of the volume occupied by organic cations, so their X-ray attenuation coefficients are comparable to the well-known oxide scintillators.

Calculation of X-ray attenuation coefficients for normal and cancerous breast tissues

The study was carried out by numerical integration based on the diffraction properties and elemental composition. The elemental compositions of breast tissues in the literature were tested. The photon attenuation coefficients calculated using the recent elemental composition were found within 0.2˗16% for adipose tissue and within 0.04˗17% for glandular tissue with the experimental reference data. The attenuation coefficients of cancerous breast tissue calculated according to the elemental content previously measured in breast cancer patients were found within 0˗17% with experimental data in the literature. The attenuation coefficients are of great interest to medical research. To calculate realistic attenuation coefficients, the characteristic coherent scatter, which is most intense at small angles, must be considered. For this reason, experimentally measured form factor data were reviewed, and the most compatible one with the theoretical form factor data produced in this study was used at low momentum transfer x (0 < x ≤ 8 nm−1). The differential linear coherent scattering distributions were calculated for an energy value of 17.44 keV and compared with their experimental counterparts.

Heavy Metal-Based Nanoparticles as High-Performance X-ray Computed Tomography Contrast Agents.

X-ray computed tomography (CT) contrast agents offer extremely valuable tools and techniques in diagnostics via contrast enhancements. Heavy metal-based nanoparticles (NPs) can provide high contrast in CT images due to the high density of heavy metal atoms with high X-ray attenuation coefficients that exceed that of iodine (I), which is currently used in hydrophilic organic CT contrast agents. Nontoxicity and colloidal stability are vital characteristics in designing heavy metal-based NPs as CT contrast agents. In addition, a small particle size is desirable for in vivo renal excretion. In vitro phantom imaging studies have been performed to obtain X-ray attenuation efficiency, which is a critical parameter for CT contrast agents, and the imaging performance of CT contrast agents has been demonstrated via in vivo experiments. In this review, we focus on the in vitro and in vivo studies of various heavy metal-based NPs in pure metallic or chemical forms, including Au, Pt, Pd, Ag, Ce, Gd, Dy, Ho, Yb, Ta, W, and Bi, and provide an outlook on their use as high-performance CT contrast agents.

Phase segmentation in X-ray CT images of concrete with implications for mesoscale modeling

X-ray computed tomography (XRCT) is a valuable tool for characterizing the microstructure of concrete and for developing 3D mesoscale numerical models directly from experimental data. However, the results of imaging and subsequent modeling are reliable only if individual phases can be identified and segmented accurately. Siliceous aggregates and cement paste are difficult to separate in XRCT images because of their similar X-ray attenuation coefficients. This work examines the quality of aggregate phase segmentation in XRCT images using (1) a standard deviation thresholding approach and (2) a random forest classification. Both approaches were validated with ground truth data for concrete samples with different aggregate volume fractions. Our findings show that either approach may successfully be used to segment aggregate phases if appropriate post-processing is performed. However, our results emphasize the critical need to preserve both aggregate size and shape during post-processing as illustrated through mesoscale modeling.

SIMPLE PHYSICAL PRINCIPLES AND MEDICAL USES OF COMPUTED TOMOGRAPHY (CT) SCAN A NEW ASSESSMENT

The development of X-ray computed tomography (CT) has been founded on the discovery of X-rays, the inception of the Radon transform, and the growth of X-ray digital data acquisition systems and computer knowledge. Dissimilar conventional X-ray imaging (general radiography), CT reconstructs cross-sectional anatomical images of the internal structures according to X-ray attenuation co-efficients (approximate tissue density) for almost every region in the body. This articleappraisals the essential physical principles and practical aspects of the CT scanner, including numerous notable evolutions in CT technology that resulted in the appearance of helical, multidetector, cone beam, portable, dual-energy, and phase-contrast CT, in integrated imaging modalities, such as positronemission- tomography一CT and single-photon-emission-computed-tomography-CT, and in clinical applications, including image acquisition parameters, CT angiography, image adjustment, versatile image visualizations, volumetric/surface rendering on a computer workstation, radiation treatment planning, and target localization in radiotherapy. The understanding of CT characteristics will provide more effective and accurate patient care in the fields of diagnostics and radiotherapy, and can lead to the improvement of image quality and the optimization of exposure doses.

Accurate measurement of effective atomic number and electron density with X-ray attenuation coefficient spectrum

Energy spectra of X-ray attenuation coefficients, μ(E)s, are measured using a system comprising a laboratory X-ray source and a photon-counting-type detector with an accuracy of 3% or less. We propose a method to derive the electron density (ρe) and effective atomic number (Zeff) of an object from measured μ(E) values. The method is based on a simple approximation in which an atomic cross-section of attenuation is expressed by a linear equation of Z4 and experimental calibration using standard materials. The μ(E) values of aqueous ethanol and acetic acid aqueous solutions are measured to get the ρes and Zeffs. The proposed method yielded a ρe value with an accuracy of 1.4% despite the use of standard materials, whereas it yielded a Zeff value with an accuracy of 1.1% for standard materials whose values of Z are similar to that of the sample.

Significant sensitivity enhancement of single crystal CdSe x-ray detector by liquid nitrogen cooling

Owing to the large x-ray attenuation coefficient, appropriate bandgap, high resistivity, and high mobility-lifetime (μτ) product, binary II–VI semiconductor CdSe is a promising x-ray detection material and it has exhibited excellent x-ray detection at room temperature (RT). For further improving the characteristics of CdSe x-ray detectors, the electrical properties of CdSe single crystals (SCs) grown through the pressure-assisted vertical Bridgman method and their x-ray detection performance have been investigated at RT and liquid nitrogen temperature (LNT), respectively. The significantly enhanced x-ray photocurrent and the prolonged response time of the devices operating at LNT indicate the photogenerated carrier lifetime could be increased by the enhanced trapping–detrapping effect obviously, and the μτ product of CdSe SCs increases from 1.39 × 10−5 to 5.34 × 10−4 cm2 V−1 with temperature lowering from RT to LNT. Meanwhile, an ultrahigh sensitivity of 5.24 × 106μC Gyair−1 cm−2 and an extremely low detection limit of 3.68 nGyair s−1 have been acquired by the CdSe SC based x-ray detectors at LNT, which is 140 times higher and 5.8 times lower than it has been at RT. Compared with conventional semiconductor x-ray detectors, the ultra-high sensitivity and extremely low detection limit of CdSe SC based detectors make their application prospects very promising.

Ultrasound-Assisted Crystallization Enables Large-Area Perovskite Quasi-Monocrystalline Film for High-Sensitive X-ray Detection and Imaging.

In recent years, halide perovskites have shown great application potential in X-ray detection due to their superior optoelectronic properties and high X-ray attenuation coefficient. However, large-area perovskite fabrication for high performance X-ray detectors remains extremely challenging. Herein, ultrasound-assisted crystallization combined with the hot-pressing method is proposed to prepare large-area (10cm × 10cm) and high-quality quasi-monocrystalline thick film of a mixed-cation perovskite MA0.42 FA0.58 PbI3 . The rapid ultrasound-assisted crystallization provides more homogeneous nucleation, which is essential to the fabrication of large-area and uniform perovskite microcrystalline film. Furthermore, the post hot-pressing treatment is implemented to fuse the crystal boundaries, rearrange the crystal grains, and eliminate the voids between crystals, resulting in a quasi-monocrystalline film. After the hot-pressing treatment, the carrier mobility and the carrier mobility-lifetime product increased about 13-fold (from 1.8 to 23.5 cm2 s-1 V-1 ) and 18 times (from 8.4 × 10-6 to 1.5 × 10-4 cm2 V-1 ), respectively. As a result, a high-performance MA0.42 FA0.58 PbI3 quasi-monocrystalline X-ray detector is achieved with an impressively high sensitivity (1.16 × 106 µC Gyair -1 cm-2 ) and low detection limit (37.4 nGyair s-1 ), demonstrating the potential of the ultrasound-assisted crystallization and hot-pressing strategy from an industrial perspective.

Two-dimensional layered nanomaterials for tumor diagnosis and treatment.

With the evolution of nanomedicine, the past decades witnessed diversified nanomaterials as marvelous anti-tumor tools ushering in a new era of tumor diagnosis and treatment. Among them, two-dimensional layered nanomaterial as an emerging class of nanomaterials has one dimension less than 100 nm, showing a high specific area and the thinnest sheet-like structure (Liu S, Pan X, Liu H. Twodimensional nanomaterials for photothermal therapy. Angew Chem Int Ed 2020;59:5890-900). The discovery of graphene drove the exploration of various new two-dimensional layered nanomaterials for tumor diagnosis and treatment including graphene-based nanomaterials, black phosphorus (BP), transition metal dichalcogenides (TMDs), layered double hydroxides (LDHs), and bismuth oxyhalides (BiOX, X=F, Cl, Br, I) (Ma H, Xue MQ. Recent advances in the photothermal applications of two-dimensional nanomaterial: photothermal therapy and beyond. J Mater Chem 2021;9:17569). On the one hand, they exhibit strong near-infrared (NIR) absorption and the capacity of optimizing corresponding properties by adjusting the crystal structure. On the other hand, they own unique strengths such as fantastic physicochemical properties (graphene-based nanomaterials), high loading capacity (BP), distinct phase-dependent optical properties (TMDs), a specific chemical response to the tumor microenvironment (LDHs), and large X-ray attenuation coefficient (BiOX). Herein, we briefly introduce three typical two-dimensional layered nanomaterials, their prospects and future research priorities in tumor diagnosis and treatment are concluded.

A review of bismuth-based nanoparticles and their applications in radiosensitising and dose enhancement for cancer radiation therapy.

About 50% of cancer patients receive radiation therapy. Despite the therapeutic benefits of this method, the toxicity of radiation in the normal tissues is unavoidable To improve the quality of radiation therapy, in addition to other methods such as IMRT, IGRT, and high radiation dose, nanoparticles have shown excellent potential when ionising radiation is applied to the target volume. Recently, bismuth-based nanoparticles (BiNPs) have become particularly popular in radiation therapy due to their high atomic numbers (Z), high X-ray attenuation coefficient, low toxicity, and low cost. Moreover, it is easy to synthesise in a variety of sizes and shapes. This study aimed to review the effects of the bismuth-based NP and its combination with other compounds, and their potential synergies in radiotherapy, discussed based on their physical, chemical, and biological interactions. Targeted and non-targeted bismuth-based NPs used in radiotherapy as radiosensitizers and dose enhancement effects are described. The results reported in the literature were categorised into various groups. Also, this review has highlighted theimportance of bismuth-based NPs in different forms of cancer treatment to find the highest efficiency for applying them as a suitable candidate for various cancer therapy and future clinical applications.

Layered BiOI single crystals capable of detecting low dose rates of X-rays

Detecting low dose rates of X-rays is critical for making safer radiology instruments, but is limited by the absorber materials available. Here, we develop bismuth oxyiodide (BiOI) single crystals into effective X-ray detectors. BiOI features complex lattice dynamics, owing to the ionic character of the lattice and weak van der Waals interactions between layers. Through use of ultrafast spectroscopy, first-principles computations and detailed optical and structural characterisation, we show that photoexcited charge-carriers in BiOI couple to intralayer breathing phonon modes, forming large polarons, thus enabling longer drift lengths for the photoexcited carriers than would be expected if self-trapping occurred. This, combined with the low and stable dark currents and high linear X-ray attenuation coefficients, leads to strong detector performance. High sensitivities reaching 1.1 × 103 μC Gyair−1 cm−2 are achieved, and the lowest dose rate directly measured by the detectors was 22 nGyair s−1. The photophysical principles discussed herein offer new design avenues for novel materials with heavy elements and low-dimensional electronic structures for (opto)electronic applications.

Multiple in-situ reactions induced by biodegradable iodides: A synergistically chemodynamic-photothermal therapy platform

Integrating multifunctional nanostructures and effectively modulating the tumor microenvironment (TME) is a need for precision nanotherapy. In this work, cuprous iodide-palladium iodides (CPIs) nanoenzymes were designed for infrared thermal (IR) and computed tomography (CT) imaging-guided synergistic chemodynamic-photothermal therapy (CDT and PTT) of tumor. CPIs act as peroxidase (POD)-like enzymes to catalyze the generation of hydroxyl radicals (OH) from endogenous H2O2, and also reduce the excess glutathione (GSH) in the TME to relieve tumor antioxidant ability, which enhance the effect of CDT. More importantly, due to the promoted non-radiative recombination of carries, the CPIs shift the light absorption range to the near-infrared region and confer higher photothermal conversion efficiency (47.72%), which improves the photothermal therapeutic effect and accelerate the generation rate of OH. Furthermore, the CT images exhibited by CPIs can help guide synergistic CDT/PTT treatment due to the high X-ray attenuation coefficient of the I-element. Finally, based on the dual oxidation of Cu(Ⅰ) and I(Ⅰ), the CPIs can be degraded to avoid long-term toxicity after inhibiting tumor growth. All in all, this nanotherapeutic platform constructed by iodides provide a possibility to simultaneously meet the biodegradability and imaging-guided synergistic chemodynamic-photothermal therapy.

Dual Nanozyme-Driven PtSn Bimetallic Nanoclusters for Metal-Enhanced Tumor Photothermal and Catalytic Therapy.

Specific generation of reactive oxygen species (ROS) within tumors in situ catalyzed by nanozymes is a promising strategy for cancer therapeutics. However, it remains a significant challenge to fabricate highly efficient nanozymes acting in the tumor microenvironment. Herein, we develop a bimetallic nanozyme (Pt50Sn50) with the photothermal enhancement of dual enzymatic activities for tumor catalytic therapy. The structures and activities of PtSn bimetallic nanoclusters (BNCs) with different Sn content are explored and evaluated systematically. Experimental comparisons show that the Pt50Sn50 BNCs exhibit the highest activities among all those investigated, including enzymatic activity and photothermal property, due to the generation of SnO2-x with oxygen vacancy (Ovac) sites on the surface of Pt50Sn50 BNCs. Specifically, the Pt50Sn50 BNCs exhibit photothermal-enhanced peroxidase-like and catalase-like activities, as well as a significantly enhanced anticancer efficacy in both multicellular tumor spheroids and in vivo experiments. Due to the high X-ray attenuation coefficient and excellent light absorption property, the Pt50Sn50 BNCs also show dual-mode imaging capacity of computed tomography and photoacoustic imaging, which could achieve in vivo real-time monitoring of the therapeutic process. Therefore, this work will advance the development of noble-metal nanozymes with optimal composition for efficient tumor catalytic therapy.