Low Energy X-ray Imaging Research Articles

Nondestructive Detection of Stem Content in Tobacco Strips Using X-Ray Imaging Analysis

Summary For tobacco strips used in cigarette production, the stem content is an important quality index to assess the impurity level of the cut leaves. The presented work developed a nondestructive detection method of stems in cut leaf agricultural products by the low energy X-ray imaging. The algorithm of stem image processing and weight calculation principle was established, and then a machine vision system with X-ray imaging and image analysis was set up to verify the quantitative detection method. The results showed that the relative error of the detection method ranged from −3.64% to 2.76%. The determination of stems with a different morphology, such as the thick stem, were also realized based on the image analysis. The accuracy of determining thick stem and long stem was 94.67% and 99.33%, respectively. The developed method is superior to the current ISO detection method of tobacco stem in leaves under the same testing conditions in terms of accuracy and efficiency, which could be applied as an effective online detection method to monitor the quality of processed leaf for cigarette production.

In-vivo imaging of a mouse by detecting bremsstrahlung X-rays from 14C using a La-GPS imaging system

ABSTRACT Imaging of 14C outside of the subject is considered to be difficult because it is a radionuclide that emits only low-energy beta particles. However, we found that bremsstrahlung X-rays form 14C could be imaged from outside of subjects and is thus applicable to in vivo small animal imaging. We developed a high-resolution low-energy X-ray imaging system using a (Gd, La)2Si2O7:Ce(La-GPS) plate combined with a flat panel photomultiplier tube (FP-PMT) for in vivo imaging of a mouse to detect the X-rays from a 14C solution administered. Without using a parallel hole collimator, accumulated 14C in the mouse’s abdomen was imaged in 1 min and dynamic in vivo imaging was possible although the spatial resolution was moderate. With a parallel hole collimator, 14C in the abdomen was obtained with a higher spatial resolution with a 60-min acquisition time. We conclude that in vivo imaging of 14C is possible by using the developed high-resolution La-GPS imaging system and may be promising for molecular imaging research.

Imaging and range estimations of prompt X-rays using YAP(Ce) camera during particle-ion irradiation to phantoms with air cavities

Low-energy X-ray imaging of prompt secondary electron bremsstrahlung X-rays (prompt X-rays) emitted during particle-ion irradiation is a promising method for range estimation. However, measurements have so far been conducted mainly for uniform phantoms of water or an acrylic block. Prompt X-ray imaging for phantoms with air cavities has not yet been extensively measured or evaluated with realistic conditions. Consequently, we conducted imaging of prompt X-rays using a pinhole YAP(Ce) camera during irradiation by protons as well as carbon ions to non-uniform acrylic phantoms with small cavities and then evaluated the images and estimated the ranges from the measured prompt X-ray images. The non-uniform acrylic phantom used for imaging had a cylindrical cavity with a 20-mm or 10-mm diameter in the phantom. During irradiation by protons or carbon ions, imaging of one of the phantoms was conducted using the pinhole YAP(Ce) camera with an air cavity as well as filling the cavity with an acrylic rod. For the phantom with a 20-mm-diameter cavity, the prompt X-ray images measured for both protons and carbon ions showed the shape of the cavity in the images, and the ranges could be estimated from the images. For the phantom with a 10-mm-diameter hole, although the shape of the hole could not be clearly observed, the ranges could also be estimated from the images. Furthermore, Monte Carlo simulated prompt X-ray images with different spatial resolution of the X-ray camera showed similar images to the measured images. We confirmed that prompt X-ray imaging of phantoms with air cavities using the pinhole YAP(Ce) cameras was possible and that prompt X-ray imaging is a promising approach for estimating the ranges for both protons and carbon ions, even for phantoms with air cavities.

Quantitative non-destructive evaluation of drilling defects in SiCf/SiC composites using low-energy X-ray imaging technique

Qualitative and quantitative non-destructive testing and evaluation (QNDT&E) of drilling defects in SiCf/SiC composites are crucial to the manufacture of hot-section components of aero-engines. A new technique for the QNDT&E of drilling defects was established based on grayscale (G) variation caused by attenuation of the relative energy (ΔE) of incident X-rays in SiCf/SiC composites. Specimens with artificial defects and actual SiCf/SiC composite components were used as test specimens. An industrial X-ray imaging system was constructed, the changes in ΔE were analysed, and the G value distribution was studied experimentally. A series of experiments on the detectability and QNDT&E of drilling defects was conducted. The results show that different drilling defects can be detected using the G value distribution and changes in the digital X-ray imaging characteristics of the SiCf/SiC composites. Plane defects, like micro-cracks with opening of 0.1 mm, can be detected. The minimum and maximum absolute deviation between the measured and designed defect sizes was close to 0.0 mm and 0.1 mm, respectively, for a Φ 0.3 mm microdefect.

Sensitivity improvement of YAP(Ce) cameras for imaging of secondary electron bremsstrahlung x-rays emitted during carbon-ion irradiation: problem and solution

Low-energy x-ray imaging of secondary electron bremsstrahlung x-rays emitted during carbon-ion irradiation is a promising method for range estimation and could be used for imaging with almost clinical dose levels of carbon ion. However, the number of counts in images with clinical dose levels is relatively small, making it difficult to obtain precise range estimations. Since improving the sensitivity of the x-ray camera may solve this issue, we developed two new types of x-ray cameras. One uses a 1 mm thick, 40 mm × 40 mm cerium-doped yttrium aluminum perovskite (YA1O3: YAP(Ce)) scintillator plate combined with a 2 inch square flat panel photomultiplier tube (FP-PMT) contained in a 2 cm thick tungsten shield with a pinhole collimator positioned 50 mm from the scintillator; the other uses a 0.5 mm thick, 20 mm × 20 mm YAP(Ce) scintillator plate combined with a 1 inch square position sensitive photomultiplier tube (PSPMT) contained in the same tungsten shield with a pinhole collimator, but with the scintillator positioned closer (30 mm) to the pinhole collimator to obtain a similar field of view. For both cameras, we used a wider angle (∼55°) pinhole collimator to measure the phantom closer to improve sensitivity. Although the 40 mm × 40 mm YAP(Ce) camera had high system spatial resolution, the background count fractions were high and produced a high count area at the center of the images due to the pulse pileup of the signals. With the 20 mm × 20 mm YAP(Ce) camera, we obtained x-ray images with low background counts without a high count area at the image center. By smoothing the measured images, we were able to estimate the ranges even for clinical dose levels. We therefore confirmed that one of our newly developed YAP(Ce) cameras had high sensitivity and is promising for the imaging of secondary electron bremsstrahlung x-rays during irradiation of carbon ions in clinical conditions.

Development of a YAP(Ce) camera for the imaging of secondary electron bremsstrahlung x-ray emitted during carbon-ion irradiation toward the use of clinical conditions

Low-energy x-ray imaging of the secondary electron bremsstrahlung (SEB) x-ray emitted during carbon-ion irradiation is a promising method for range estimation. However, it remains unclear whether the method can be used for imaging with the clinical dose levels of carbon-ion and whether the bremsstrahlung x-ray can be detected from the deeper part of the body. To clarify these points, we developed a new high resolution low-energy x-ray camera and conducted imaging of the SEB x-ray during the irradiation of carbon-ions of different energies and intensities. Imaging was also tried with an x-ray camera using a human-head-sized, 17 cm diameter cylindrical phantom. To develop a high resolution imaging detector for a low-energy x-ray, we used a 20 × 20 × 0.5 mm thick cerium-doped yttrium aluminum perovskite, YA1O3 (YAP(Ce)) scintillator plate, which was optically coupled to a 25 mm square high quantum efficiency (HQE) type position sensitive photomultiplier tube (PSPMT). The imaging detector was encased in a 2 cm thick tungsten container and a pinhole collimator was attached to its camera head. After evaluating the camera’s performance, SEB x-ray imaging was tried during irradiation of the carbon-ion and compared the results with a Monte Carlo simulation. We imaged the beam tracks by the SEB x-ray in real-time during irradiation of the carbon-ion and imaging and range estimation were possible even with near clinical dose level of 7.5 × 108 particles of carbon-ion. Clear images of a SEB x-ray were also obtained for a 17 cm diameter cylindrical phantom. The measured images were good agreement with the Monte Carlo simulation. We confirmed that our developed YAP(Ce) camera is promising for imaging SEB x-rays during irradiation of carbon-ions even near clinical conditions.

Upscaling the Production of High Temperature Polymer Electrolyte Membrane Fuel Cells – an Assessment of Reproducibility, Performance and Durability

A fast and simple method for catalyst layer quality control on large surfaces has been introduced in the electrode production process for high temperature polymer electrolyte membrane fuel cells. Based on these results, the produced materials have been improved, resulting in the reduction of the frequency of defect occurrence and the improvement of performance, durability and reproducibility of the resulting membrane-electrode-assemblies. The obtained materials have been successfully operated at 0.4 A cm-2 at 160 °C under wet reformate on the anode and compressed air on the cathode for over 750 h, giving 600 mV without any indication of degradation. One MEA was selected for post-mortem investigation by low-energy X-ray imaging. With this method, defects of the electrode were visualized and an indication for phosphoric acid loss identified. Further experiments are planned in order to verify the effect of the observed defects on the fuel cell behaviour.

Rapid, Non-destructive Inspection and Classification of Inhalation Blisters Using Low-Energy X-ray Imaging

Dry powders packaged in aluminum foil blisters are an increasingly common dosage form found in inhalation drug products. Filling of inhalation blisters often involves compressing bulk aerated powder into dense compacts. Sealed blisters are conditioned, e.g., by ultrasonic vibration, to loosen the consolidated powder within, to enable ready dispersion to a respirable aerosol when actuated by an inhaler device. Currently, the presence of residual powder consolidation within the blister is monitored manually by cutting open blisters for visual inspection. X-ray imaging has gained increased acceptance as a non-destructive analytical technique for pharmaceutical capsules and tablets, typically with masses on the order of ~ 100 mg. Here, an X-ray inspection approach was investigated for inhalation blisters having a significantly smaller powder fill mass of 2 mg. The challenge of sensing a small powder mass (2 mg) packaged within a significantly heavier blister (~ 75 mg) was met using a low-energy X-ray imaging system. The measurement principle relies on denser, consolidated powder appearing as darker regions in the recorded image. Proof-of-concept experiments were performed using empty blister strips, and blister strips filled with 2 mg of placebo powder, half of which were subjected to ultrasonic conditioning. The tests demonstrated that a supervised machine learning approach based on digitally processed X-ray images reliably distinguished between the three types of blisters tested, i.e., empty blisters and conditioned and un-conditioned blisters of 2-mg fill mass. Using independent training and validation sets of 948 images each, an automated classification accuracy ≥ 99.8% was demonstrated.

Online Detection in the Separation Process of Tobacco Leaf Stems as Biomass Byproducts Based on Low Energy X-Ray Imaging

Stems often need to be separated from leaves and used alone as biomass byproducts in the agro-processing industry involving utilization of crops leaves. However, an effective method to detect stems from leaves is needed. In this study, X-ray imaging combined with digital photography analysis was applied to online detection of stems from threshed tobacco leaves. The optimal conditions for the inspection system were: X-ray radiation intensity of 70 keV, detection belt speed of 1.6 m/s, and gray threshold of 40,000. The free stems and leaf strips containing stems were used as target samples to validate the method. The test results showed that identification accuracies for both free stems and leaf strips containing stems were >98.0%. When leaf strips containing stems were mixed with pure leaves, identification accuracy of stems was 94.5%, and rejecting accuracy was 92.0%. These results indicate that this method is a reliable classification solution for threshed tobacco leaves.

Research on dual energy grating based X-ray phase contrast imaging

There exist some problems in a grating-based X-ray differential phase contrast imaging system, such as complex imaging system, low imaging efficiency and high requirements for step precision. The phase information extraction method of imaging system has been developed into an existing two-stepping phase shift method from the original phase stepping method, which improves the imaging efficiency and reduces the imaging radiation dose and imaging time. However, the method of two-stepping phase shift still needs to move the grating, and the requirement for accuracy of the step position is also very high. According to the problems mentioned above, in this paper we propose a dual energy multi-line X-ray source and a dual energy analysis grating. The dual energy multi-line X-ray source can emit two different levels of X-ray structure light, which can replace the X-ray source and source grating. The dual energy analysis grating is composed of two different types of scintillator materials, which are in staggered distribution. One is scintillator material that can transform high energy X-ray into visible light, and the other one can convert low energy X-ray into visible light. The dual energy analysis grating can replace traditional analysis grating and the conversion screen of X-ray CCD detector. By using the dual energy multi-line X-ray source and dual energy analysis grating in grating-based X-ray differential phase contrast imaging system, a dual energy grating-based X-ray phase contrast imaging system is proposed in this paper. In addition, in this paper we show the structure and imaging principle of the imaging system. The imaging system can achieve high and low energy X-ray imaging without moving grating. Two levels of X-ray imaging are equivalent to the analysis grating displacement π phase, which is in line with the traditional two-stepping method of two image phase shift requirements. Therefore, after the normalization processing of the two kinds of energies, the phase information can be extracted by the traditional two-stepping phase shift method. In order to validate the correctnesses of the imaging principle of the proposed imaging system and extraction method of phase information, the imaging system is simulated. The simulation is performed on the assumption that an X-ray beam passes through a polymethyl methacrylate sphere as a phase specimen, and the method is adopted by using the proposed dual energy X-ray about left and right lumbar imaging to extract phase information. The simulation result shows that the imaging system can realize normal imaging, and the first-order derivative distribution of the sphere phase extracted by the dual energy X-ray method is consistent with the experimental result.

Assessment of low energy X-ray imaging for magnetic and gold nanoparticles

Introduction Gold and magnetic nanoparticles (NPs) are already used as contrast agents in CT and MRI diagnosis respectively, as well as in hyperthermia treatments. In both cases it is very important to be able to determine in vivo the distribution of the NPs. This can be done by radiolabeling the NPs or via MRI. These methods however present serious drawbacks in terms of cost and complexity. Purpose The purpose of this study is to explore and standardize a procedure of in vivo X-ray imaging for magnetic and gold NPs for diagnostic and pre-therapeutic purposes, using this low-cost, simple, readily available technology. Materials and methods The measurements were carried out on a prototype bench top x-ray system, consisting of an X-ray tube of a maximum beam energy of 80 keV and a minimum focal spot of 33 μm and of a CMOS detector with an active area of 12 × 12 cm and a spatial resolution of 0.1 mm. NPs samples of concentrations ranging between 1 and 500 mg of substance/ml were studied and compared with standard iodine solutions. Results All substances are found to present significant contrast enhancement properties and are used to create a standardized imaging procedure with respect to their concentrations. Gold nanoparticles are easily seen in lower concentrations and dual energy subtraction offers a greater differentiation in the observed attenuation properties. Localization and distribution information can be obtained in vivo through X-ray imaging. Conclusion A standardized procedure of in vivo X-ray imaging is set up for magnetic and gold NPs for diagnostic and pre-therapeutic purposes. Disclosure There is no relationship to be disclosed that may bias this presentation.

First results of a Double-SOI pixel chip for X-ray imaging

Aiming at low energy X-ray imaging, a prototype chip based on Double-SOI process was designed and tested. The sensor and pixel circuit were characterized. The long lasting crosstalk issue in SOI technology was understood. The operation of pixel was verified with a pulsed infrared laser beam. The depletion of sensor revealed by signal amplitudes is consistent with the one revealed by I–V curve. An s-curve fitting resulted in a sigma of 153 e− among which equivalent noise charge (ENC) contributed 113 e−. It's the first time that the crosstalk issue in SOI technology was solved and a counting type SOI pixel demonstrated the detection of low energy radiation quantitatively.

Determining the platinum loading and distribution of industrial scale polymer electrolyte membrane fuel cell electrodes using low energy X-ray imaging

Low energy X-ray imaging (E < 25 keV) is herein demonstrated to be a rapid, effective and non-destructive tool for the quantitative determination of the platinum loading and distribution over the entire geometric area of gas diffusion electrodes for polymer electrolyte membrane fuel cells. A linear correlation was found in order for the average image grayscale intensity to be calibrated to the platinum loading, while the platinum distribution was mapped across the electrode geometric area. The resolution was found to be sufficient in identifying flaws and inhomogeneities in the catalyst layer of electrodes fabricated using an industrial spraying process. This technique proves to be an attractive option for the electrode performance study, the process optimization and quality control of electrode fabrication on an industrial scale.

Reassessment of structural shielding design in mammography installations

In this article, it is argued that current shielding methodologies can lead to an over-shielding of low-energy X-ray imaging facilities. Measurements of scattered air kerma rates in a mammography installation, including the effect of an anthropomorphic phantom of the patient, are presented. Detailed Monte Carlo calculations that support the measured results are also shown. Calculations for a mobile mammography installation, including the 'patient transmission factor', are presented and results are discussed.

Validity of spherical approximations of initial charge cloud shape in silicon detectors

Spherical approximation has been used extensively in low-energy X-ray imaging to represent the initial charge cloud produced by photon interactions in silicon detectors, mainly because of its simplicity. However, for high-energy X-rays, where the initial charge distribution is as important as the diffusion process, the spherical approximation will not result in a realistic detector response. In this paper, we present a bubble-line model that simulates the initial charge cloud in silicon detectors for photons in the energy range of medical imaging. An initial charge cloud can be generated by sampling the center of gravity and the track size from statistical distributions derived from Monte Carlo generated tracks and by distributing a certain proportion of photon energy into a bubble (68%) and a line portion uniformly. The simulations of detector response demonstrate that the new model simulates the detector response accurately and corresponds well to Monte Carlo simulation.

Characterization of imaging performance of a large-area CMOS active-pixel detector for low-energy X-ray imaging

Abstract We report the imaging characteristics of the recently developed large-area complementary metal-oxide-semiconductor (CMOS) active-pixel detector for low-energy digital X-ray imaging applications. The detector consists of a scintillator to convert X-ray into light and a photodiode pixel array made by the CMOS fabrication process to convert light into charge signals. Between two layers, we introduce a fiber-optic faceplate (FOP) to avoid direct absorption of X-ray photons in the photodiode array. A single pixel is composed of a photodiode and three transistors, and the pixel pitch is 96 μm. The imaging characteristics of the detector have been investigated in terms of modulation-transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). From the measured results, the MTF at the Nyquist frequency is about 20% and the DQE around zero-spatial frequency is about 40%. Simple cascaded linear-systems analysis has showed that the FOP prevents direct absorption of X-ray photons within the CMOS photodiode array, leading to a lower NPS and consequently improved DQE especially at high spatial frequencies.

Fast binary readout front-end electronics for silicon strip detectors for low energy x-ray imaging applications

A binary readout architecture of multichannel front-end electronics used in a position-sensitive measurement system provides fully parallel signal processing, including data storage, and is the best one to cope with high intensity x-ray radiation. However, for low x-ray energy applications, the noise and matching performance of multichannel ASIC impose contradictory requirements on the high rate capability of the front-end electronics. These important aspects of ASIC design are analysed in this paper for two different generations of multichannel ASICs produced in CMOS technology and dedicated to low energy x-ray imaging applications using a silicon strip detector.

Growth of thick CdTe epilayers on GaAs substrates and evaluation of CdTe/n+-GaAs heterojunction diodes for an X-ray imaging detector

The growth characteristics of thick (100) CdTe epitaxial layers of a thickness up to 200 µm on a (100) GaAs substrate in a metal-organic vapor-phase epitaxy (MOVPE) system and fabrication of CdTe/n+-GaAs heterojunction diodes for their possible applications in low-energy x-ray imaging detectors are reported. The grown epilayers were of high structural quality as revealed from the x-ray double-crystal rocking curve (DCRC) analysis, where the full-width at half-maximum (FWHM) values of the (400) diffraction peaks was between 50 arcsec and 70 arcsec. The 4.2-K photoluminescence (PL) showed high-intensity bound-excitonic emission and very small defect-related peaks. The heterojunction diode fabricated had a good rectification property with a low value of reverse-bias current. The x-ray detection capability of the diode was examined by the time-of-flight (TOF) measurement, where good bias-dependent photoresponse was observed, but no carrier transport property could be deduced. It was found that the CdTe layer has a large number of trapping states as attributed to the cadmium-related vacancy and Ga-impurity, diffused from the substrate, related defect complexes.

Application of a plastic scintillating fiber array for low-energy x-ray imaging

Interest in digital imaging has led to the development of new detectors in the form of large-area displays. Most of the recent improvements are based on charge-coupled devices, a:Si photodiodes arrays, and so on. Some of these photodetectors must be coupled to scintillating screens to convert the ionizing radiation into light. Fiber-optic screens offer an advantage for achieving this interface because the length (thickness) of the interaction medium does not contribute too much to the degradation of the spatial resolution. We discuss the possibility of using a plastic scintillating fiber (PSF) array for x-ray detection and imaging in the 10-keV range. Modulation-transfer-function (MTF) measurements of the PSF array are compared with the optics MTF of the imaging system (without the sample); cross talk in the fiber array is negligible, even though the fiber array thickness is 20 mm. The optimal thickness of the array is estimated experimentally.

EUV Astrophysics with ALEXIS: The Wide View

The Array of Low Energy X-ray Imaging Sensors (ALEXIS) satellite is Los Alamos’ pathfinding small space mission achieving low cost and rapid development time for its technology demonstration and science goals. The ALEXIS satellite contains the ALEXIS telescope array, which consists of six EUV/ultrasoft X-ray telescopes utilizing normal incidence multilayer mirrors, microchannel plate detectors, and thin UV rejecting filters. Each telescope is tuned to a relatively narrow bandpass centered at either 130, 171, or 186 angstroms. Each telescope has a 33° field-of-view, and a resolution of ~ 0.25°. With each 50 s rotation of the satellite, the telescopes scan most of the anti-solar hemisphere of the sky. The spacecraft is controlled exclusively from a ground station located at Los Alamos.This paper discusses the characteristics and performance of the ALEXIS telescopes and the results from the mission in spite of the damage incurred to the spacecraft at launch.