BACKGROUND:X-ray fluorescence (XRF) imaging is a promising modality for quantitative molecular imaging that allows for the in vivo biodistribution detection of specific elements within biological systems. Despite its potential, challenges such as detection limit and scan time have hindered its widespread adoption in preclinical in vivo imaging. PURPOSE:This study aims to address these challenges by developing a benchtop 2D multi-pinhole XRF imaging system with an up-to-date cadmium zinc telluride (CZT) detector system without tomographic reconstruction. METHODS:The benchtop 2D multi-pinhole XRF imaging system was implemented by integrating a High Energy x-ray Imaging Technology (HEXITEC) 2 × 2 CZT detector system with a lead collimator containing four tungsten pinholes. 140 kV fan beam x-rays irradiated a small-animal-sized polymethyl methacrylate (PMMA) phantom filled with gold nanoparticle (GNP) solutions at concentrations of 0.156, 0.313, 0.625, 1.25, 2.5, and 5.0 mg/mL. A GNP-loaded phantom with varying concentrations was used to establish a calibration curve relating GNP concentrations to K-shell XRF photon counts and to evaluate the detection limit of the system. RESULTS:The multi-pinhole collimator generated four well-aligned, nonoverlapping projections, each centered on a CZT module, resulting in a fourfold increase in photon detection efficiency compared with a single-pinhole collimator. The detector exhibited excellent spectral performance with an energy resolution of 1.38 ± 0.32 keV full width at half maximum (FWHM) at 59.5 keV. As a result, two gold K α ${K_\alpha }$ XRF peaks (67.0 and 68.8 keV) were well resolved. Reconstructed XRF images, generated by combining four projections using the maximum likelihood expectation maximization algorithm, showed a strong linear relationship between GNP concentrations and XRF photon counts (R2 > 0.99). The benchtop 2D multi-pinhole XRF imaging system demonstrated in this study achieved a detection limit of 0.105 mg/mL with a scan time of 10 min and an imaging dose of 51.5 cGy. CONCLUSIONS:By successfully integrating a multi-pinhole collimator with the HEXITEC 2 × 2 CZT detector system, the benchtop 2D multi-pinhole XRF imaging system substantially improved system sensitivity, achieving a detection limit of 0.1 mg/mL for GNPs, a biologically relevant concentration, in a small-animal-sized phantom. This detection limit was attained with a 10-min scan time and an imaging dose of 51.5 cGy, both within the acceptable range for in vivo imaging applications. These results highlight the potential of the benchtop 2D multi-pinhole XRF imaging system for preclinical in vivo applications.

The development of fourth-generation synchrotrons, including the Diamond-II upgrade, promises 10-100× flux increases, reaching up to 1012 photons s-1 mm-2 at the detector, across a broad range of energies from 20 to 100 keV. To exploit fully these impressive photon fluxes and high X-ray energies, readout chips must achieve high frame rates and dynamic ranges, while the use of high-Z sensor materials is essential. To address these challenges, the UK's Science and Technology Facilities Council has developed DynamiX, a test structure for a novel two-stage charge cancellation circuit on a 65 nm CMOS process with a dynamic range from single photon(s) per pixel per frame to >9000 photons per pixel per frame (1011-1012 photons s-1 mm-2) at 20 keV photon energy. The application-specific integrated circuit has 16 ×16 pixels on 110 µm pitch and is hybridized with 2 mm thick Redlen high-flux cadmium zinc telluride (HF-CdZnTe). Data are read out at 534000 frames per second over a 14 Gbps serialiser and frames are assembled and saved with a custom data acquisition system. Measurements were made on the Diamond Light Source (DLS) B16 Test Beamline using monochromatic X-ray beams of different sizes and energies to evaluate the detector performance. A sub-pixel beam of size ∼60 µm × ∼15 µm was used to probe pixels to measure single photons with a noise performance of σ = 5.7 ± 0.1 keV. These single photons are used to calibrate the test pulse and pixel cancellation packet sizes. The linearity of the detector response under increasing flux was measured from <1 photon per pixel per frame to ∼109 photons s-1 mm-2 at 20 keV with an r.m.s. linearity of 6.2%. A polychromatic X-ray set was used to reach higher fluxes of ∼3 × 1010 photons s-1 mm-2 (20 keV equivalent), yielding an r.m.s. linearity of 3.2%. Finally, the full sensor area was used to image a rotating slitted disc at 534000 frames per second.

Irregular Li heterostructure growth at the interphase between the solid electrolyte and anode reduces solid-state Li metal battery (SSLMB) performance, but the fundamental cause is still elusive. Measuring and imaging Li ^+ ion diffusion in operando inside an SSLMB using a commercially standard cell configuration are extremely challenging because the ultra-light Li element exhibits a minute signal-to-noise ratio using most x-ray-related characterization methods, and the weak x-ray signals of Li ^+ are buried by strong signals of other heavy transition metal elements in the cathode and battery enclosure. Here, we pioneer novel operando correlative imaging of coupling x-ray Compton scattering with computed tomography (XCS-CT), which is able to quantify the interplay between spatially resolved Li ^+ ion diffusion kinetics and Li ^0 metal structure growth at the interphases of both the anode and cathode sides inside a full-cell SSLMB using a solid polymer electrolyte (SPE) and commercially standard cell configuration during (dis)charging. We show a 61% increase in the efficiency of extracting Li ^+ ions from the cathode LiNi _0.6 Mn _0.2 Co _0.2 O _2 to the anode during charging at 0.1 C compared with at 1 C due to restricted Li ^+ ion diffusion at the higher rate inside SSLMB. However, this led to the formation of a more irregular interfacial morphology, consisting not only of Li ^0 dendrites, but also sub-surface pore formation at the anode/SPE interphase. We find that surprisingly, the irregular Li ^0 structure initiation and growth are accelerated during the first Li stripping step, not the Li plating step, and the root cause is the onset imbalance of Li ^+ ion diffusion and redox reactions between the anode and cathode. These insights highlight the benefits of asymmetric charging and discharging rates as a promising solution to improving SSLMB performance with SPEs. The operando correlative XCS-CT imaging technique has the potential to study the relationship between active ion concentrations and buried morphological changes for a variety of battery chemistries.

Fe-rich intermetallic compounds (IMCs) are a persistent challenge in the recirculation of secondary aluminium alloys. Despite significant research effort, largely via post-solidification studies, the mechanisms governing IMC phase selection in higher-Fe (> 1 wt.%), recycled Al alloys and how they can be controlled to facilitate more benign IMC species and/or morphologies remain poorly understood. This creates barriers to compositional and process design for more Fe-tolerant alloys. In this paper, we present a systematic real-time investigation of IMC formation, phase selection and morphological evolution in recycled 3xx series Al alloys with elevated Fe concentrations (up to 2.5 wt%), using in situ synchrotron X-ray radiography. Coupled with thermodynamic simulations, we develop a method to reliably estimate the formation temperatures of primary alpha-AlFeSi and beta-AlFeSi IMCs, and show direct insights into their formation sequence and kinetics. Contrary to widely held assumptions based on low Fe-containing (<0.6 wt%) primary alloys, we show that in recycled alloys containing higher Fe concentrations, increased cooling rate significantly promotes the formation of the more anisotropic beta-AlFeSi (over the more compact alpha-AlFeSi), which however can be fully suppressed at slow cooling. We propose how a solute-suppression mechanism kinetically controls the a//1 IMC phase evolution. Further, we reveal and quantify a faceted-to-non-faceted morphological transition of alpha-AlFeSi from a faceted polyhedral to non-faceted near-equiaxed dendritic morphology. This transition is governed by an interplay between solidification velocity and liquid undercooling at the local IMC/liquid interfaces. This study provides insights into how solidification conditions may be leveraged to improve microstructural control in high Fe-containing recycled alloys.

There is a rising interest in Single Photon Emission Computed Tomography (SPECT) imaging systems with improved energy resolution to facilitate multi-functional molecular imaging applications, such as alpha-emitter radiopharmaceutical therapy (α-RPT). In this paper, we report the design and evaluation of the Alpha-SPECT-Mini system that offers an ultrahigh energy resolution and high sensitivity for small animal studies. The Alpha-SPECT-Mini system is constructed based on small-pixel CdTe detectors that offers sub-1keV Full-Width-Half-Maximum (FWHM) energy resolution for single pixel events and an average ~2.5keV energy resolution at 122 keV and ~3.5 keV at 218 keV over 153600 pixels in the system. This allows to easily identify X- and gamma-ray contributions in densely populated spectra, such as from the Ac-225 decay chain. The system uses a 96-loft-hole collimator and six stationary detection panels in a full ring geometry. Finally, the system performance is demonstrated using Tc-99m- and Ac-225-filled resolution and image quality (IQ) phantoms. We have experimentally demonstrated that the Alpha-SPECT-Mini is a high-performance imaging system capable of imaging alpha-emitters in preclinical applications.

Lead-free perovskite-inspired materials have emerged as promising candidates for direct X-ray detection. However, in the early exploration of emerging materials, the focus was on large single crystals. Herein, we report a facile, scalable, single-step synthesis of high-quality Cs3Bi2I9 nanocrystals (NCs) directly from their precursor powders through an ultrasonication approach. The large-scale synthesis of the NCs allowed for the production of 0.78 cm2 pellets used in the fabrication of X-ray detection devices, which exhibit a high bulk resistivity of 1 × 1011 Ω cm and a low dark current density of 3.3 nA cm-2 under an applied bias of 50 V (357 V cm-1 electric field). These devices achieve a limit detection of 108 nGyair s-1, an order of magnitude improvement over the a-Se used in commercial medical imaging, along with stable current under continuous X-ray exposure with a peak energy of 35 keVp. Finally, we demonstrate the scale-up of these detectors by producing thick films 9 cm2 in area, achieving a performance comparable to that of the detectors based on pellets.

The advent of metal-based drugs and metal nanoparticles as therapeutic agents in anti-tumor treatment has motivated the advancement of X-ray fluorescence computed tomography (XFCT) techniques. An XFCT imaging modality can detect, quantify, and image the biodistribution of metal elements using the X-ray fluorescence signal emitted upon X-ray irradiation. However, the majority of XFCT imaging systems and instrumentation developed so far rely on a single or a small number of detectors. This work introduces the first full-ring benchtop X-ray fluorescence emission tomography (XFET) system equipped with 24 solid-state detectors arranged in a hexagonal geometry and a 96-pinhole compound-eye collimator. We experimentally demonstrate the system’s sensitivity and its capability of multi-element detection and quantification by performing imaging studies on an animal-sized phantom. In our preliminary studies, the phantom was irradiated with a pencil beam of X-rays produced using a low-powered polychromatic X-ray source (90kVp and 60W max power). This investigation shows a significant enhancement in the detection limit of gadolinium to as low as 0.1 mg/mL concentration. The results also illustrate the unique capabilities of the XFET system to simultaneously determine the spatial distribution and accurately quantify the concentrations of multiple metal elements.

Perovskite single crystal-based self-powered direct X-ray detectors demonstrate promising performances that rival those of commercial technologies in terms of sensitivity and detection limit. However, surface defects, particularly those induced via post-polishing, detrimentally limit the performance of direct X-ray detectors. In this study, we synthesized perovskite single crystal with composition of $\mathrm{FA}_{0.85} \mathrm{MA}_{0.1} \mathrm{Cs}_{0.05} \mathrm{~Pb}\left(\mathrm{I}_{0.85} \mathrm{Br}_{0.15}\right)_{3}$ and implemented a chemical passivation approach to mitigate defects and improved detector performances. We employed a double-side passivation strategy, wherein we deposited a reactive organic salt of phenethylammonium iodide. This salt exhibits reactivity specifically towards the defective perovskite sites, facilitating the formation of lower-dimensional perovskite layers on both the bottom and top surfaces of the crystal. Chemical passivation leads to a significant reduction in defects, resulting in low dark current with high sensitivity of $3.7 \times 10^{3} \mu \mathrm{C} / \mathrm{Gy} \mathrm{cm}^{2}$ to X-ray responses in the X-ray detector. The detector shows an indicative response for single-photon gamma-ray detection. These findings highlight the practical applications of chemically passivating defects in perovskite single crystals for high performance $\mathrm{X} / \gamma$-ray detectors.

In this paper, results are presented from the characterisation of Redlen Technologies high-flux-capable Cadmium Zinc Telluride (HF-CZT) hybridised to the HEXITECMHz ASIC, a novel 1 MHz continuous X-ray imaging system. A 2 mm thick HF-CZT HEXITECMHz detector was characterised on the B16 Test Beamline at the Diamond Light Source and displayed an average FWHM of 850 eV for monochromatic X-rays of energy 20 keV. Measurements revealed a shift in the baseline of irradiated pixels that results in a movement of the entire spectrum to higher ADU values. Datasets taken to analyse the effect's dynamics showed it to be highly localised and flux-dependent, with the excess leakage current generated equivalent to per-pixel shifts of similar to 543 pA (8.68 nA mm(-2)) at a flux of 1.26x10(7) ph s(-1) mm(-2). Comparison to results from a p-type Si HEXITECMHz device indicate this `excess leakage-current' effect is unique to HF-CZT and it is hypothesised that it originates from trapping at the electrode-CZT interface and a temporary modification of the potential barrier between the CZT and metal electrode.

Understanding the correlation between chemical and microstructural properties is critical for unraveling the fundamental relationship between materials chemistry and physical structures that can benefit materials science and engineering. Here, we demonstrate novel in situ correlative imaging of the X-ray Compton scattering computed tomography (XCS-CT) technique for studying this fundamental relationship. XCS-CT can image light elements that do not usually exhibit strong signals using other X-ray characterization techniques. This paper describes the XCS-CT setup and data analysis method for calculating the valence electron momentum density and lithium-ion concentration, and provides two examples of spatially and temporally resolved chemical properties inside batteries in 3D. XCS-CT was applied to study two types of rechargeable lithium batteries in standard coin cell casings: (1) a lithium-ion battery containing a cathode of bespoke microstructure and liquid electrolyte, and (2) a solid-state battery containing a solid-polymer electrolyte. The XCS-CT technique is beneficial to a wide variety of materials and systems to map chemical composition changes in 3D structures.

The formation of heterogeneous Li structures at the anode/solid polymer electrolyte (SPE) membrane interphase of solid-state Li-metal batteries (SSLMBs) is one of the key factors that impede SSLMB performance. The relationship between Li+-ion transport kinetics and Li0 structural evolution at the buried interphase is critical but challenging to characterize. Here, we report an operando correlative X-ray Compton scattering and computed tomography imaging technique that quantifies the changes of Li+-ion concentrations in the bulk cathode, SPE membrane, and anode of the SSLMB full cell using a commercially standard configuration. We then visualize Li+-ion concentration distributions as well as Li0 microstructures at the buried anode/SPE interphase. Mechanistic analyses show that the Li-stripping step forms more irregular interfacial Li morphologies at the expense of bulk anode volume shrinkage compared to the Li-plating step during the first cycle.

Spectroscopic X-ray imaging techniques including Compton X-ray Imaging, X-ray Fluorescence Imaging and Hyperspectral X-ray Tomography require energy-resolving detectors capable of operating at high incident X-ray fluxes to make time resolved measurements. HEXITECMHz, operates at a continuous 1 MHz frame rate and can make fully spectroscopic measurements at >10(6) ph s(-1) mm(-2). This is enabled by an integrating Front End, in-pixel digitisation and high-speed serialisers. A 300 mu m thick p-type Si HEXITECMHz detector was characterised on the B16 Test Beamline at the Diamond Light Source and are the first measurements taken at a 1 MHz frame rate. At 10 keV and 15 keV) the device displayed average FWHM of 656 eV and 682 eV respectively, with minimal changes in spectroscopic performance over similar to 8 h. Analysis of charge-sharing events show low charge loss and a linear energy-signal response. Higher-flux measurements illustrated the capability of the ASIC to operate as a photon-counting device.

Online proton range verification is a rapidly emerging field characterised by its ability to reduce the error margins during proton beam therapy, as it is patient-specific and in vivo. In particular, secondary prompt gamma detection is a promising tool to monitor the dose delivery. The present research evaluates the capability of a HEXITEC detector to identify the prompt gammas produced during proton beam therapy, and assesses its potential for online range verification. To achieve this, the detector is placed at one side of a water phantom, which is irradiated at different proton energies in the University College London Hospital Proton Centre. For further analysis, Monte Carlo simulations are performed using Geant4 and the same geometry as the experiment. The results show that HEXITEC has the potential to be part of a detection system that could identify secondary prompt gammas within the secondary field produced inside the target, allowing for the in-detector discrimination of these particles via cluster size analysis. The comparison between data sets shows that there is a high level of accuracy between the model and the experimental measurements in terms of secondary flux and charge diffusion inside the detector, which poses the model as a fundamental tool for future optimisation studies.

The HEXITEC MHz ASIC is the next generation of the STFC's High Energy X-ray Imaging Technology (HEXITEC). With a ×100 increase in the camera frame rate to 1 MHz, the new ASIC is capable of delivering fully spectroscopic X-ray imaging at photon fluxes of 2×10 6 photons s -1 mm -2 . The improved flux capability ensures the relevance of the technology at a new generation of difraction-limited storage ring (DLSR) synchrotrons as well as enabeling dynamic spectroscopic imaging with sub-keV energy resolution to be carried out on millisecond timescales. In this paper preliminary results from X-ray testing of a 0.3 mm thick p-type Si sensor and 2.0 mm thick HF-CdZnTe sensor at the Diamond Light Source Synchrotron are presented for the first time. Each module consists of 80 × 80 pixels on a 250 μm pixel pitch operated at a temperature of 20°C and a frame rate of 1 MHz. For these preliminary measurements, testing was completed using a prototype test system which limited readout to a portion of the 1 MHz output sampled over an SPI test interface at ∼50 Hz. Despite this limitation these measurements allow the spectroscopic performance of the ASIC to be characterised ahead of the full DAQ system. The prototype detectors were characterised using monochromatic X-rays with energies 12–35 keV at fluxes of (0.6 – 2.5) × 10 6 photons s -1 mm -2 . At an X-ray energy of 12 keV, the energy resolution of the p-type Si and HF-CdZnTe detectors were measured to be 1.0 keV and 1.1 keV respectively. At the higher energies of 20 keV and 35 keV the energy resolution in the HF-CdZnTe was measured to be 1.2 keV and 1.4 keV respectively.

Increasing electrode thickness is gaining more attention as a potential route to increase energy density for Li ion batteries although the realizable capacity and rate capability are usually limited by Li+ ion diffusion during (dis)charge, especially at increased (dis)charge rates. It remains challenging to visualize and quantify the low atomic number Li+ chemical stoichiometry distribution inside the electrode within commercially standard battery geometry, e.g. coin cells with stainless steel casings. Here, we map the distribution of Li + chemical stoichiometry in the electrode microstructure inside a working coin cell battery to show the amount of electrode materials contributing to energy storage performance using innovative in situ correlative full -field X-ray Compton scattering imaging (XCS-I) and X-ray computed tomography (XCT). We design and fabricate an ultra-thick (-1 mm) cathode of LiNi0.8Mn0.1Co0.1O2 with a microstructure containing vertically oriented pore arrays using a directional ice templating method. This novel technique paves a new way to map low atomic number elements in 3D structures and study how the microstructure improves Li + ion diffusivity and energy storage performance.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

A Monte Carlo model was developed to simulate the response of a pixelated hyperspectral CdZnTe (CZT) X-ray detector. The first part of the simulation was carried out using Geant4 to obtain a list of energy depositions inside the CZT crystal. The second part of the simulation used charge transport equations to calculate the size of the electron charge cloud, as it drifts under the influence of an electric field to be read out. Experimentally acquired data from an Am-241 source with the high energy X-ray imaging technology (HEXITEC) detector were compared to simulated data, and good agreement was found. The model was used to investigate the energy dependence of fluorescence and charge-sharing effects. The probability of producing an escaped fluorescence photon was quantified as a function of primary photon energy. As expected, at primary photon energies just above the K-edge of Cd, there was a greater chance of producing an escaped fluorescence photon, and this probability decreased as the primary photon energy increased. The probability of an event being shared across multiple pixels as a function of primary photon energy was quantified. It was found that as the primary photon energy was increased, there was a greater chance of producing an event shared across multiple pixels. The detector response to a Bremsstrahlung spectrum was simulated. Using previous results, fluorescence and charge-sharing effects were corrected for, giving a corrected spectrum in good agreement with the input spectrum.