Conventional X-ray Imaging System Research Articles

Staring X-ray backscatter imaging based on ultra-high aspect ratio lobster eye lens.

In contrast to conventional X-ray imaging systems, the lobster eye lens, serving as a pivotal component for X-ray focusing, presents the potential for downsizing X-ray backscatter imaging systems. This study reports the successful implementation of a pioneering non-contact staring X-ray backscatter imaging experiment, with the target positioned 1.5 meters away from the system and employing a tube voltage of 60 kV for the X-ray light source. The system is built upon a novel high aspect ratio (500) meridian lobster eye lens, employing a laboratory low illuminance desktop light source and a commercial X-ray detector to achieve high-resolution focused imaging of hard X-rays. Point spread function testing and a series of imaging experiments were carried out to assess the resolution and optimal imaging photon energy of the proposed system. Furthermore, according to the characteristics of the point spread function of the cross image of the lobster eye lens, we proposed an image processing algorithm. The experimental results demonstrate that, after processing, the Structural Similarity (SSIM) Index of the backscatter image and the ground truth image can be improved from an average of 0.0526 to 0.5758. Our research significantly contributes to the advancement of a new generation of X-ray backscatter imaging systems.

Elimination of wraparound artifacts in spatial harmonic imaging using motion blurring

Dark-field X-ray imaging (DFXI), which is based on spatial harmonic imaging (SHI), is an imaging modality that can rapidly and easily acquire microstructural information on macroscopic samples that cannot be detected by conventional X-ray imaging systems. It has potential in various fields. However, it cannot obtain accurate information concerning microstructures, owing to image distortion caused by wraparound artifacts. In this study, we examined the use of motion-blurring technique to eliminate these artifacts and devised a modified motion condition for a tilted grid system designed to prevent moiré artifacts in SHI-based DFXI. Experimental results indicated that the technique successfully eliminated the artifacts in dark-field images and increased the contrast-to-noise ratio for small-angle X-ray scattering signals, which are the measures of microstructural information of the sample. Furthermore, the technique increased the accuracy of detection of low-density foreign bodies in SHI-based DFXI-particularly when the sample had sharp edges. The results indicate the applicability of motion-blurring technique to SHI-based DFXI.

Inclusion of a GaAs detector model in the Photon Counting Toolkit software for the study of breast imaging systems.

We present an upgraded version of the Photon Counting Toolkit (PcTK), a freely available by request MATLAB tool for the simulation of semiconductor-based photon counting detectors (PCD), which has been extended and validated to account for gallium arsenide (GaAs)-based PCD(s). The modified PcTK version was validated by performing simulations and acquiring experimental data for three different cases. The LAMBDA 60 K module planar detector (X-Spectrum GmbH, Germany) based on the Medipix3 ASIC technology was used in all cases. This detector has a 500-μm thick GaAs sensor and a 256 × 256-pixel array with 55 μm pixel size. The first validation was a comparison between simulated and measured spectra from a 109Cd radionuclide source. In the second validation study, experimental measurements and simulations of mammography spectra were generated to observe the performance of the GaAs version of the PcTK with polychromatic radiation used in conventional x-ray imaging systems. The third validation study used single event analysis to validate the spatio-energetic model of the extended PcTK version. Overall, the software provided a good agreement between simulated and experimental data, validating the accuracy of the GaAs model. The software could be an attractive tool for accurate simulation of breast imaging modalities relying on photon counting detectors and therefore could assist in their characterization and optimization.

Visual Evaluation of Image Quality of a Low Dose 2D/3D Slot Scanner Imaging System Compared to Two Conventional Digital Radiography X-ray Imaging Systems.

The purpose of this study was to assess the image quality of the low dose 2D/3D slot scanner (LDSS) imaging system compared to conventional digital radiography (DR) imaging systems. Visual image quality was assessed using the visual grading analysis (VGA) method. This method is a subjective approach that uses a human observer to evaluate and optimise radiographic images for different imaging technologies. Methods and materials: ten posterior-anterior (PA) and ten lateral (LAT) images of a chest anthropomorphic phantoms and a knee phantom were acquired by an LDSS imaging system and two conventional DR imaging systems. The images were shown in random order to three (chest) radiologists and three experienced (knee) radiographers, who scored the images against a number of criteria. Inter- and intraobserver agreement was assessed using Fleiss’ kappa and weighted kappa. Results: the statistical comparison of the agreement between the observers showed good interobserver agreement, with Fleiss’ kappa coefficients of 0.27–0.63 and 0.23–0.45 for the chest and knee protocols, respectively. Comparison of intraobserver agreement also showed good agreement with weighted kappa coefficients of 0.27–0.63 and 0.23–0.45 for the chest and knee protocols, respectively. The LDSS imaging system achieved significantly higher VGA image quality compared to the DR imaging systems in the AP and LAT chest protocols (p < 0.001). However, the LDSS imaging system achieved lower image quality than one DR system (p ≤ 0.016) and equivalent image quality to the other DR systems (p ≤ 0.27) in the knee protocol. The LDSS imaging system achieved effective dose savings of 33–52% for the chest protocol and 30–35% for the knee protocol compared with DR systems. Conclusions: this work has shown that the LDSS imaging system has the potential to acquire chest and knee images at diagnostic quality and at a lower effective dose than DR systems.

Quantitative Image Quality Metrics of the Low-Dose 2D/3D Slot Scanner Compared to Two Conventional Digital Radiography X-ray Imaging Systems.

The aim of this study was to determine the quantitative image quality metrics of the low-dose 2D/3D EOS slot scanner X-ray imaging system (LDSS) compared with conventional digital radiography (DR) X-ray imaging systems. The effective detective quantum efficiency (eDQE) and effective noise quantum equivalent (eNEQ) were measured using chest and knee protocols. Methods: A Nationwide Evaluation of X-ray Trends (NEXT) of a chest adult phantom and a PolyMethylmethacrylate (PMMA) phantom were used for the chest and knee protocols, respectively. Quantitative image quality metrics, including effective normalised noise power spectrum (eNNPS), effective modulation transfer function (eMTF), eDQE and eNEQ of the LDSS and DR imaging systems were assessed and compared. Results: In the chest acquisition, the LDSS imaging system achieved significantly higher eNEQ and eDQE than the DR imaging systems at lower and higher spatial frequencies (0.001 ≤ p ≤ 0.044). For the knee acquisition, the LDSS imaging system also achieved significantly higher eNEQ and eDQE than the DR imaging systems at lower and higher spatial frequencies (0.001 ≤ p ≤ 0.002). However, there was no significant difference in eNEQ and eDQE between DR systems 1 and 2 at lower and higher spatial frequencies (0.10 < p < 1.00) for either chest or knee protocols. Conclusion: The LDSS imaging system performed well compared to the DR systems. Thus, we have demonstrated that the LDSS imaging system has the potential to be used for clinical diagnostic purposes.

Detail Restoration and Tone Mapping Networks for X-Ray Security Inspection

X-ray imaging is one of the most widely used security measures for maintaining airport and transportation security. Conventional X-ray imaging systems typically apply tone-mapping (TM) algorithms to visualize high-dynamic-range (HDR) X-ray images on a standard 8-bit display device. However, X-ray images obtained through traditional TM algorithms often suffer from halo artifacts or detail loss in inter-object overlapping regions, which makes it difficult for an inspector to detect unsafe or hazardous objects. To alleviate these problems, this article proposes a deep learning-based TM method for X-ray inspection. The proposed method consists of two networks called detail-recovery network (DR-Net) and TM network (TM-Net). The goal of DR-Net is to restore the details in the input HDR image, whereas TM-Net aims to compress the dynamic range while preserving the restored details and preventing halo artifacts. Since there are no standard ground-truth images available for the TM of X-ray images, we propose a novel loss function for unsupervised learning of TM-Net. We also introduce a dataset synthesis technique using the Beer-Lambert law for supervised learning of DR-Net. Extensive experiments comparing the performance of our proposed method with state-of-the-art TM methods demonstrate that the proposed method not only achieves visually compelling results but also improves the quantitative performance measures such as FSITM and HDR-VDP-2.2.

Preliminary evaluation of stationary inverse-geometry digital tomosynthesis system for diagnostic applications: A simulation study

Conventional X-ray imaging systems for diagnosis have several issues such as high radiation dose, structure superposition, and complicated geometry. These issues can be solved by providing 3D cross-sectional images with limited dose and simplifying system geometries. The purpose of this study is to implement a stationary inverse-geometry digital tomosynthesis (s-IGDT) system through simulation and evaluate the performance of the s-IGDT system for diagnostic applications. We also investigated the digital radiography (DR) and conventional digital tomosynthesis (DT) images for comparison. The simulated s-IGDT system was modeled with a linear X-ray source array contained 75 focal spots and a flat-panel detector. The linear X-ray source array and detector were stationary during image acquisition. In order to reduce truncation artifacts, a raw data correction process was performed. We measured profile, signal difference-to-noise ratio (SDNR), contrast-to-noise ratio (CNR) and root-mean-square error (RMSE) for a comparison of image quality among the s-IGDT, DR and conventional DT. The results showed that the SDNR, CNR and quantitative accuracy of the s-IGDT were higher than those of the DR and similar with those of the conventional DT. Also, the spatial resolution of the s-IGDT evaluated by modulation transfer function (MTF) was comparable with the conventional DT. Therefore, the s-IGDT proposed in this study has a feasibility for diagnostic applications and a potential as an alternative to the conventional X-ray imaging system.

Luminescence imaging of water during irradiation of X-ray photons lower energy than Cerenkov- light threshold

Luminescence imaging of water using X-ray photon irradiation at energy lower than maximum energy of ~200keV is thought to be impossible because the secondary electrons produced in this energy range do not emit Cerenkov- light. Contrary to this consensus assumption, we show that the luminescence imaging of water can be achieved by X-ray irradiation at energy lower than 120keV. We placed water phantoms on a table with a conventional X-ray imaging system, and luminescence images of these phantoms were measured with a high-sensitivity, cooled charge coupled device (CCD) camera during X-ray photon irradiation at energy below 120keV. We also carried out such imaging of an acrylic block and plastic scintillator. The luminescence images of water phantoms taken during X-ray photon irradiation clearly showed X-ray photon distribution. The intensity of the X-ray photon images of the phantom increased almost proportionally to the number of X-ray irradiations. Lower-energy X-ray photon irradiation showed lower-intensity luminescence at the deeper parts of the phantom due to the higher X-ray absorption in the water phantom. Furthermore, lower-intensity luminescence also appeared at the deeper parts of the acrylic phantom due to its higher density than water. The intensity of the luminescence for water was 0.005% of that for plastic scintillator. Luminescence imaging of water during X-ray photon irradiation at energy lower than 120keV was possible. This luminescence imaging method is promising for dose estimation in X-ray imaging systems.

Reconstruction method for grating-based x-ray phase-contrast images without knowledge of the grating positions

To retrieve the phase information of x-rays using a Talbot-Lau interferometer, the knowledge of the grating positions is mandatory. Transferring the interferometer technique from the laboratory to a conventional x-ray imaging system, this requirement is no longer guaranteed. This is due to distortions and vibrations which are coupled into the interferometer. Therefore, we applied a principal-component analysis to Talbot-Lau x-ray phase-contrast data. In experiments we compared this alternative approach for image reconstruction to the conventional procedure. As a result, a superior robustness of the principal-component analysis against imperfect phase-stepping data was found. Furthermore, using the proposed method, the reconstruction of x-ray phase-contrast images from randomly distributed phase-step positions is possible.

Metallic Contaminant Detection System Using Multi-Channel Superconducting Quantum Interference Device (SQUID)

Metallic particles with outer dimensions smaller than 100 microns in Li-ion battery cannot be detected using a conventional X-ray imaging system. We propose two systems using high Tc SQUIDs: One is a direct detection type and the other is an indirect type. In the direct detection system, an object with a contaminant is magnetized by a permanent magnet and then the remanent field of the contaminant is detected by SQUID. In the indirect detection system, the principle is based on Faradays law of electromagnetic induction. The diameter of the detection coil is 2 to 3 times larger than the SQUID; as a result, less number of SQUIDs, two or three is enough to inspect a specimen with a width of 65 mm. This method is applicable for an inspection of metallic contaminants in non-magnetic film such as a separator for Li-ion battery. We discuss the results of the evaluation of the new system as compared with a direct detection system.

Measurement of skin dose from cone-beam computed tomography imaging

ObjectiveTo measure surface skin dose from various cone-beam computed tomography (CBCT) scanners using point-dosimeters.Materials & methodsA head anthropomorphic phantom was used with nanoDOT optically stimulated luminescence (OSL) dosimeters (Landauer Corp., Glenwood, IL) attached to various anatomic landmarks. The phantom was scanned using multiple exposure protocols for craniofacial evaluations in three different CBCT units and a conventional x-ray imaging system. The dosimeters were calibrated for each of the scan protocols on the different imaging systems. Peak skin dose and surface doses at the eye lens, thyroid, submandibular and parotid gland levels were measured.ResultsThe measured skin doses ranged from 0.09 to 4.62 mGy depending on dosimeter positions and imaging systems. The average surface doses to the lens locations were ~4.0 mGy, well below the threshold for cataractogenesis (500 mGy). The results changed accordingly with x-ray tube output (mAs and kV) and also were sensitive to scan field of view (SFOV). As compared to the conventional panoramic and cephalometric imaging system, doses from all three CBCT systems were at least an order of magnitude higher.ConclusionsPeak skin dose and surface doses at the eye lens, thyroid, and salivary gland levels measured from the CBCT imaging systems were lower than the thresholds to induce deterministic effects. However, our findings do not justify the routine use of CBCT imaging in orthodontics considering the lifetime-attributable risk to the individual.

Development of Metallic Contaminant Detection System Using Eight-Channel High- $T_{c}$ SQUIDs

In this paper, a roll-to-roll eight-channel (8-ch) high- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tc</i> superconducting quantum interference device (SQUID) detection system for magnetic contaminants in a lithium-ion (Li-ion) battery anode sheet was developed. Finding ultra-small metallic foreign matter is an important issue for a manufacturer because metallic contaminants carry the risk of an internal short. When contamination occurs, the manufacturer of the product suffers a great loss from recalling the tainted product. Metallic particles with outer dimensions smaller than 100 μm cannot be detected using a conventional X-ray imaging system. Therefore, a highly sensitive detection system for small foreign matter is required. We have already developed a detection system based on a single-channel SQUID gradiometer and horizontal magnetization. For practical use, the detection width of the system should be increased to at least 65 mm by employing multiple sensors. In this paper, we present an 8-ch high- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tc</i> SQUID roll-to-roll system for inspecting a Li-ion battery anode with a width of 65 mm. A special microscopic type of a cryostat was developed upon which eight SQUID gradiometers were mounted. As a result, small iron particles of φ35 μm on a real Li-ion battery anode with a width of 70 mm were successfully detected. This system is practical for the detection of contaminants in a Li-ion battery anode sheet.

Parallel-X-Ray Imaging for Improving Spatial Resolution

X-ray imaging with a high spatial resolution is essential for observing small features inside an object. We examined a new parallel X-ray imaging system to improve the spatial resolution of a conventional projection-type X-ray imaging system. Parallel X-rays were obtained by using a polycapillary optic, which had a parabolic shape, combined with an X-ray tube. The field of view of the imaging system was limited by the diameter of the polycapillary optic. In the proposed parallel X-ray imaging system, a spatial resolution of 12 lp/mm was achieved. The parallel X-ray imaging system is expected to be useful for examining a small field with high spatial resolution.

X-ray imaging with the PILATUS 100k detector

We report on the application of the PILATUS 100K pixel detector for medical imaging. Experimental results are presented in the form of X-ray radiographs using standard X-ray absorption contrast and a recently developed phase contrast imaging method. The results obtained with the PILATUS detector are compared to results obtained with a conventional X-ray imaging system consisting of an X-ray scintillation screen, lens optics, and a charge coupled device. Finally, the results for both systems are discussed more quantitatively based on an image power spectrum analysis.

Model MTF for Conventional X-ray Imaging Systems

A simple MTF formula for the X-ray imaging process has been derived taking into account the size of the X-ray focus, off-focus radiation, scattered radiation from the object, and position of the imaged layer within the object. This formula has been confirmed experimentally using a lead test raster. It refers to an object model consisting of a variable depth object layer within a homogeneous water medium.

Low-Dosage X-Ray Imaging System Employing Flying Spot X-Ray Microbeam (Dynamic Scanner)

A new low-dosage x-ray imaging system employing a flying spot x-ray microbeam provides: (a) patient exposure to a fraction of the radiation used in conventional x-ray imaging systems; (b) computer-controlled dynamic measurement for ultra-low dosage x-ray diagnosis; and (c) higher resolution images at lower x-ray dosages in computed tomography.