X-ray Tube Source Research Articles

X-ray absorption spectroscopy combined with deep learning for auto and rapid illicit drug detection

ABSTRACT Background: X-ray absorption spectroscopy (XAS) is a widely used substance analysis technique. It bases on the different absorption coefficients at different energy level to achieve material identification. Additionally, the combination of spectral technology and deep learning can achieve auto detection and high accuracy in material identification. Objectives: Current methods are difficult to identify drugs quickly and nondestructively. Therefore, we explore a novel approach utilizing XAS for the detection of prohibited drugs with common X-ray tube source and photon-counting (PC) detector. Method: To achieve automatic, rapid, and accurate detection of drugs. A CdTe detector and a common X-ray source were used to collect data, then dividing the data into training and testing sets. Finally, the improved transformer encoder model was used for classification. LSTM and ResU-net models are selected for comparation. Result: Fifty substances, which are isomers or compounds with similar molecular formulas of drugs, were selected for experiment substances. The results showed that the improved transformer model achieving 1.4 hours for training time and 96.73% for accuracy, which is better than the LSTM (2.6 hours and 65%) and ResU-net (1.5 hours and 92.7%). Conclusion: It can be concluded that the attention mechanism is more accurate for spectral material identification. XAS combined with deep learning can achieve efficient and accurate drug identification, offering promising application in clinical drug testing and drug enforcement.

Optimization of contrast and dose in x-ray phase-contrast tomography with a Talbot-Lau interferometer

X-ray phase-contrast imaging has become a valuable tool for biomedical research due to its improved contrast abilities over regular attenuation-based imaging. The recently emerged Talbot-Lau interferometer can provide quantitative attenuation, phase-contrast and dark-field image data, even with low-brilliance x-ray tube sources. Thus, it has become a valid option for clinical environments. In this study, we analyze the effects of x-ray tube voltage and total number of images on the contrast-to-noise ratio (CNR) and dose-weighted CNR (CNRD) calculated from tomographic transmission and phase-contrast data of a phantom sample. Constant counting statistics regardless of the voltage was ensured by adjusting the image exposure time for each voltage setting. The results indicate that the x-ray tube voltage has a clear effect on both image contrast and noise. This effect is amplified in the case of phase-contrast images, which is explained by the polychromatic x-ray spectrum and the dependence of interferometer visibility on the spectrum. CNRD is additionally affected by the total imaging time. While submerging the sample into a water container effectively reduces image artefacts and improves the CNR, the additional attenuation of the water must be compensated with a longer exposure time. This reduces dose efficiency. Both the CNR and CNRD are higher in the phase-contrast images compared to transmission images. For transmission images, and phase-contrast images without the water container, CNRD can be increased by using higher tube voltages (in combination with a lower exposure time). For phase-contrast images with the water container, CNRD is increased with lower tube voltages. In general, the CNRD does not strongly depend on the number of tomographic angles or phase steps used.

Size characterization of x-ray tube source with sphere encoded imaging method.

In x-ray imaging, the size of the x-ray tube light source significantly impacts image quality. However, existing methods for characterizing the size of the x-ray tube light source do not meet measurement requirements due to limitations in processing accuracy and mechanical precision. In this study, we introduce a novel method for accurately characterizing the size of the x-ray tube light source using spherical encoded imaging technology. This method effectively mitigates blurring caused by system tilting, making system alignment and assembly more manageable. We employ the Richardson-Lucy algorithm to iteratively deconvolve the image and recover spatial information about the x-ray tube source. Unlike traditional coded imaging methods, spherical coded imaging employs high-Z material spheres as coding elements, replacing the coded holes used in traditional approaches. This innovation effectively mitigates blurring caused by system tilting, making system alignment and assembly more manageable. In addition, the mean square error is reduced to 0.008. Our results demonstrate that spherical encoded imaging technology accurately characterizes the size of the x-ray tube light source. This method holds significant promise for enhancing image quality in x-ray imaging.

High spatial resolution direct conversion amorphous selenium X-ray detectors with monolithically integrated CMOS readout

Recent progress in the field of micron-scale spatial resolution direct conversion X-ray detectors for high-energy synchrotron light sources serve applications ranging from nondestructive and noninvasive microscopy techniques which provide insight into the structure and morphology of crystals, to medical diagnostic measurement devices. Amorphous selenium (a-Se) as a wide-bandgap thermally evaporated photoconductor exhibits ultra-low thermal generation rates for dark carriers and has been extensively used in X-ray medical imaging. Being an amorphous material, it can further be deposited over large areas at room temperatures and at substantially lower costs as compared to crystalline semiconductors. To address the demands for a high-energy and high spatial resolution X-ray detector for synchrotron light source applications, we have thermally evaporated a-Se on a Mixed-Mode Pixel Array Detector (MM-PAD) Application Specific Integrated Circuit (ASIC). The ASIC format consists of 128 × 128 square pixels each 150 μm on a side. A 200 μm a-Se layer was directly deposited on the ASIC followed by a metal top electrode. The completed detector assembly was tested with 45 kV Ag and 23 kV Cu X-ray tube sources. The detector fabrication, performances, Modulation Transfer Function (MTF) measurements, and simulations are reported.

Laboratory-scale X-ray absorption spectrometer with a cylindrical Johansson crystal analyzer

X-ray absorption fine structure spectroscopy (XAFS) can accurately provide information on the local structure and chemical state of matter and is an important method in material research. XAFS experiments are performed at a synchrotron radiation facility. However, owing to the limited access to these oversubscribed beamtimes, it is difficult to access such large facilities for routine but important experiments. In this study, we present a laboratory-scale X-ray absorption spectrometer for XAFS measurements. The spectrometer comprises a homemade cylindrical Johansson crystal analyzer, conventional X-ray tube source, silicon drift detector, and precision Rowland circle scanning mechanism. The use of a cylindrical Johansson crystal analyzer enables the spectrometer to obtain higher energy resolution compared to a Johann-type spherically bent crystal analyzer. To demonstrate the performance of the laboratory-scale X-ray absorption spectrometer, we further measured the XAFS of 10μm thick copper foil and 5μm thick nickel, and the results were consistent with those obtained from synchrotron radiation measurements. Our results highlight that the X-ray absorption spectrometer can achieve sufficient energy resolution even at a low Bragg angle, which implies that there is no need to replace the crystal analyzers when measuring the XAFS of different samples.

Monochromatic computed tomography using laboratory-scale setup

In this article, we demonstrate the viability of highly monochromatic full-field X-ray absorption near edge structure based tomography using a laboratory-scale Johann-type X-ray absorption spectrometer utilising a conventional X-ray tube source. In this proof-of-concept, by using a phantom embedded with elemental Se, Na_2SeO_3, and Na_2SeO_4, we show that the three-dimensional distributions of Se in different oxidation states can be mapped and distinguished from the phantom matrix and each other with absorption edge contrast tomography. The presented method allows for volumetric analyses of chemical speciation in mm-scale samples using low-brilliance X-ray sources, and represents a new analytic tool for materials engineering and research in many fields including biology and chemistry.

Materials Separation via the Matrix Method Employing Energy-Discriminating X-ray Detection

The majority of lab-based X-ray sources are polychromatic and are not easily tunable, which can make the 3D quantitative analysis of multi-component samples challenging. The lack of effective materials separation when using conventional X-ray tube sources has motivated the development of a number of potential solutions including the application of dual-energy X-ray computed tomography (CT) as well as the use of X-ray filters. Here, we demonstrate the simultaneous decomposition of two low-density materials via inversion of the linear attenuation matrices using data from the energy-discriminating PiXirad detector. A key application for this method is soft-tissue differentiation which is widely used in biological and medical imaging. We assess the effectiveness of this approach using both simulation and experiment noting that none of the materials investigated here incorporate any contrast enhancing agents. By exploiting the energy discriminating properties of the detector, narrow energy bands are created resulting in multiple quasi-monochromatic images being formed using a broadband polychromatic source. Optimization of the key parameters for materials separation is first demonstrated in simulation followed by experimental validation using a phantom test sample in 2D and a small-animal model in 3D.

An achromatic X-ray lens

Diffractive and refractive optical elements have become an integral part of most high-resolution X-ray microscopes. However, they suffer from inherent chromatic aberration. This has to date restricted their use to narrow-bandwidth radiation, essentially limiting such high-resolution X-ray microscopes to high-brightness synchrotron sources. Similar to visible light optics, one way to tackle chromatic aberration is by combining a focusing and a defocusing optic with different dispersive powers. Here, we present the first successful experimental realisation of an X-ray achromat, consisting of a focusing diffractive Fresnel zone plate (FZP) and a defocusing refractive lens (RL). Using scanning transmission X-ray microscopy (STXM) and ptychography, we demonstrate sub-micrometre achromatic focusing over a wide energy range without any focal adjustment. This type of X-ray achromat will overcome previous limitations set by the chromatic aberration of diffractive and refractive optics and paves the way for new applications in spectroscopy and microscopy at broadband X-ray tube sources.

Reduction of Compton Background Noise for X-ray Fluorescence Computed Tomography with Deep Learning

For bench-top X-ray fluorescence computed tomography (XFCT), the X-ray tube source will bring extreme Compton background noise, resulting in a low signal-to-noise ratio and low contrast detection limit. In this paper, a noise2noise denoising algorithm based on the UNet deep learning network is proposed. The network can use noise image learning to convert the noise image into a clean image. Two sets of phantoms (high concentration Gd phantom and low concentration Bi phantom) are used for scanning to simulate the imaging process under different noise levels and generate the required data set. Additionally, the data set is generated by Geant4 simulation. In the training process, the L1 loss function is used for its good convergence. The image quality is evaluated according to CNR and pixel profile, which shows that our algorithm is better than BM3D, both visually and quantitatively.

Development and assessment of an x-ray tube-based multi-beam x-ray scatter projection imaging system.

Coherent scatter x-ray imaging systems are sensitive to material structure and chemical composition, and generate soft-material images with contrast superior to conventional transmission x-ray imaging. For practicality in medical or security applications, the image data acquisition time should be <10 min. Our approach is a multi-beam projection imaging design. Previously, as a development stage, we implemented a synchrotron-based system with five coplanar pencil beams and continuous motion of the object. In the work reported here, we developed a more practical coherent scatter projection imaging system using a conventional x-ray tube source. The object is irradiated by an array of up to three rows by five columns of pencil beams, and motorized stages translate the object through the beams for step-and-shoot acquisition. For the same tube loading, broad spectrum beams, such as 110 kVp filtered with 2.25 mm Al, were found to provide a higher signal-difference-to-noise ratio between soft materials in scatter images than lower kVp, more heavily filtered beams that have a narrower, lower intensity spectrum. The shortest acquisition time for a 6.0 × 10.0 cm2 object with 6000 pixels was 8.8 min. The width of a sharp edge in the scatter image was consistent with the pencil beam diameter. Contrast-detail performance was similar to our synchrotron-based system. In this first x-ray tube-based system, for simplicity, the transmitted x rays are measured through attenuators using the same flat-panel detector that measures scattered x rays. As a result, the primary image quality was reduced.

Development of a hard X-ray detector for measuring continuous spectra generated by runaway electrons in VEST

A hard X-ray measurement system is developed to observe the activities of runaway electrons in versatile experiment spherical torus (VEST) at Seoul National University. The detection system provides information on the generation of runaway electrons by detecting hard X-rays from its bremsstrahlung radiation. To acquire such information, the X-ray spectrum at several tens to hundreds of keV at the maximum is reconstructed using signals from four thin scintillation detectors with different energy sensitivities, and the spectrum is converted to the original X-ray energy. The unfolding process is implemented by an artificial neural network model trained using a measured X-ray spectrum generated by an X-ray tube source at 50 to 320 keV. The system would reveal the generation mechanism of runaway electrons during plasma discharges with various MHD activities in VEST to mitigate and suppress runaway electrons.

Valence-to-core X-ray emission spectroscopy of titanium compounds using energy dispersive detectors.

X-ray emission spectroscopy (XES) of transition metal compounds is a powerful tool for investigating the spin and oxidation state of the metal centers. Valence-to-core (vtc) XES is of special interest, as it contains information on the ligand nature, hybridization, and protonation. To date, most vtc-XES studies have been performed with high-brightness sources, such as synchrotrons, due to the weak fluorescence lines from vtc transitions. Here, we present a systematic study of the vtc-XES for different titanium compounds in a laboratory setting using an X-ray tube source and energy dispersive microcalorimeter sensors. With a full-width at half-maximum energy resolution of approximately 4 eV at the Ti Kβ lines, we measure the XES features of different titanium compounds and compare our results for the vtc line shapes and energies to previously published and newly acquired synchrotron data as well as to new theoretical calculations. Finally, we report simulations of the feasibility of performing time-resolved vtc-XES studies with a laser-based plasma source in a laboratory setting. Our results show that microcalorimeter sensors can already perform high-quality measurements of vtc-XES features in a laboratory setting under static conditions and that dynamic measurements will be possible in the future after reasonable technological developments.

Assessment of Backscattered Radiation Dose at Exposed Object’s Level during X-Ray Examinations

This paper estimates backscattered radiation doses at patient’s positioning level (exposed object) using different X-ray tubes. The effects of different exposure sittings (X-ray tube voltage, exposure intensity, exposed area, dosimeter position, and distance between X-ray tube and imaged object surface) on backscattered radiation doses are estimated using different dosimeters and x-ray units. The quantity of recorded backscattered radiation dose -which reflects from patient’s table or bucky to image receptor and exposed patient - is determined by the position of dosimeter between exposed object’s table or bucky and X-ray tube according to backscatter angle, at higher backscattered angle, the dosimeter records more backscattered dose. The results showed that, increase in kVp, exposure intensity, and exposed area led to a concomitant increase in the quantity of backscattered radiation, whereas the Increase in distanc e between X-ray tube (source) and imaged object surface reduces the amount of backscattered radiation dose. As well as, there is no remarkable difference in recorded backscattered dose due to the position of X-ray tube or the direction of incident X-ray photons.

Simple and fast scattering information in X-ray grating-based phase-contrast imaging

X-ray grating-based phase-contrast imaging is a potential imaging method with pre-clinical and clinical applications because it has the possibility of a large field of view and is compatible with X-ray tube sources. However, in X-ray grating-based phase-contrast imaging extraction methods have great importance to retrieve and separate information enabling high acquisition speed, reduced exposure dose and improved mechanical stability. Phase-stepping is a widely used extraction method in X-ray grating-based phase-contrast imaging. However, its discontinuous mode of acquisition leads to worse mechanical stability, exposure dose is generally high, which limits clinical applications significantly. In this work, the integrating bucket method is translated from visible light to X-ray regime, to extract scattering information of the investigated object. Both theoretical derivations with numerical simulation and experiments were performed to confirm the veracity and feasibility of the proposed method. In addition, we present the advantages of the proposed method over the phase-stepping method.

Design of X-ray units for inspection applications (review)

A review of the structural elements (individual components, printed circuit boards, etc.) of X-ray systems intended for inspection of electronic products is presented. The basic principles of constructing such systems and typical composition of the equipment capable of providing the minimum necessary functionality are considered. Among the main technical characteristics an emphasis is made on the resolution power, which depends on the pixel size and thickness of the scintillator layer of the X-ray detector, as well as on the size of the effective focal spot of the X-ray tube. Comparative analysis of the advantages and shortcomings of clastic (open type) and sealed (closed type) X-ray tubes – one of the main nodes of such systems-is carried out. A structural diagram of a clastic X-ray tube is presented along with and the characteristics of domestic and foreign developments. The main disadvantages of the systems based on clastic tubes are considered. Large dimensions, large weight, relative complexity of the construction, presence of the vacuum-tight collapsible connections, the necessity of using a pumping system providing high vacuum, the necessity of high-voltage training of the tube assemblies after their replacement, and high cost are noted separately. The design of sealed off BS microfocus X-ray tube and radiation sources on their base which can be used in the development of domestic X-ray systems are briefly described. The diameter and length of the metal-glass cylinder tube are 75 and 315 mm, and the diameter and length of the copper anode tube 10 and 100 mm, respectively. A tungsten target is deposited on a beryllium substrate (X-ray tube exit window) with a thickness of 0.2 mm. The minimum focal length during x-ray photography is 0.5 mm. A comparative analysis of the characteristics of a clastic (collapsible) X-ray tube with continuous pumping and an X-ray tube sealed from an exhaust cart revealed the possibility of successful use of sealed tubes in modern X-ray systems used for inspection applications.

4D spatiotemporal evolution of liquid spray using kilohertz-rate x-ray computed tomography.

Four-dimensional (x,y,z,t) x-ray computed tomography was demonstrated in an optically complex spray using an imaging system consisting of three x-ray sources and three high-speed detectors. The x-ray sources consisted of high-flux rotating anode x-ray tube sources that illuminated the spray from three lines of sight. The absorption, along each absorption path, was collected using a CsI phosphor plate and imaged by a high-speed intensified CMOS camera at 20kHz. The radiographs were converted to a quantitative equivalent path length (EPL) of liquid using a variable attenuation coefficient to account for beam hardening. The EPL data were then reconstructed using the algebraic reconstruction technique into high-speed time sequences of the three-dimensional liquid mass distribution.

A detector system for a high-energy phase-contrast human computed tomography experimental device

Abstract A detector system is designed for a high-energy phase-contrast computed tomography (CT) experimental device with an X-ray tube voltage of 80 kV. The spot size of the X-ray tube is 0.4 mm*0.7 mm. The Gd2O2S scintillator detector is adopted in our design, which is characterized by a high detection efficiency and high light yield. This system contains 2304 channels and the corresponding high-density read-out electronics. Considering the influence of the large spot size of the X-ray tube source, a detector pixel size of 0.75 mm*1 mm is adopted to obtain sufficient spatial resolution. Because the light intensity fluctuation caused by the phase shift is very weak, a 20bit ADC is used to achieve sufficient efficient resolution (ER). The electronics test shows that the SNR can reach 72. Compared to a commercial detector board, the detector system has better resolution for the sample used in the phase-contrast imaging experiment.

Ex Situ and Operando Characterization of Energy Storage Materials By Benchtop XAFS and XES

Advanced x-ray spectroscopies permit the interrogation of a material’s local electronic structure in an element-specific manner. In particular, these techniques reveal the speciation and ligand environment of an electroactive element and can provide direct insight into the state-of-charge and state-of-health of a battery. Despite their utility, the scientific impact of advanced x-ray spectroscopies is necessarily constrained by the availability of instrumentation. For x-ray absorption fine structure (XAFS) and x-ray emission spectroscopy (XES), studies are traditionally performed at synchrotron x-ray facilities. These facilities frequently serve to push the forefront of science and, as a result, necessarily operate under an access model which excludes projects which require routine analytical characterization, rapid feedback, or regular access. Over the last four years, our group at the University of Washington has developed several families of laboratory-based instruments to expand the accessibility of advanced x-ray spectroscopies. For the study of transition metal chemistry, we have constructed two Rowland circle spectrometers based upon related designs. Both spectrometers provide energy resolutions comparable to that observed at a synchrotron endstation. Their designs are also highly efficient, allowing studies to be completed with commercial x-ray tube sources in time scales relevant for materials research programs. For many such studies, the instrumentation can generate satisfactory spectra in a matter of minutes, permitting operando studies of battery materials at charge rates in excess of 1C. From the standpoint of instrumentation, a brief review of the present designs is presented with emphasis on recent advances in extended-XAFS capabilities. Differences between the spectrometer designs and the advantages of each will also be highlighted. Regarding materials inquiry, a survey of the above instrument’s application to energy storage research is provided. This will include XAFS analyses of two systems of nanoparticle compounds which were engineered to be catalysts or pseudocapacitors. These results will facilitate a review of the information attainable from the underlying technique. The rich electronic structure of vanadyl phosphate cathode materials, as well a suite of vanadium oxides, is probed via valence-to-core XES (VTC-XES). Finally, operando x-ray absorption near-edge structure (XANES) results obtained from a pouch cell containing a nickel-rich NMC cathode at a variety of charge rates are presented.

Johann-type laboratory-scale x-ray absorption spectrometer with versatile detection modes.

We present a low-cost laboratory X-ray absorption spectrometer that uses a conventional X-ray tube source and bent Johann-type crystal monochromators. The instrument is designed for X-ray absorption spectroscopy studies in the 4-20 keV range which covers most K edges of 3d transition metals and L edges of 5d transition metals and actinides. The energy resolution is typically in the range of 1-5 eV at 10 keV depending on the crystal analyser and the Bragg angle. Measurements can be performed in transmission, fluorescence, and imaging modes. Due to its simple and modular design, the spectrometer can be modified to accommodate additional equipment and complex sample environments required for in situ studies. A showcase of various applications is presented.

Advantages of Al based GEM detector aimed at plasma soft−semi hard X-ray radiation imaging

Development of gaseous detectors, more specifically Gas Electron Multiplier (GEM) based detectors, for application at tokamak plasma radiation monitoring/imaging in Soft−Semi Hard X-ray (S−SH) region is an ongoing research activity aiming to deliver valuable information on plasma shape, magnetic configuration, non-axisymmetry phenomena of the plasma, etc. Wide radiation range and brightness of plasma radiation impose some restrictions on choice of materials in the detecting chamber, as their interaction with the incident radiation may disrupt original signals.This work proposes usage of aluminum as GEM foils electrodes for the first time. The detector based on these foils was constructed and examined. The operational characteristics and spectral capabilities of such detector were compared with the ones based on the standard (commonly used) copper GEM foils. The laboratory tests were performed using X-ray tube and 55Fe sources to examine detectors’ capabilities in energy-resolved imaging. Additionally, simulations of origin and number of the generated electrons, which determine the detector signal, were performed for Al and Cu GEM foils for a wide energy range of incident photons. The experimental and modelling data demonstrated that Cu based GEM detector produces higher parasitic signal than Al one necessitating total elimination of copper from detector’s chamber.