Image Simulation Research Articles

Radiology resident proficiency in identifying misplaced lines, tubes, and devices: a simulation-based study using WIDI SIM.

Accurate placement of medical devices is crucial in critical care to prevent severe complications. This study aims to evaluate radiology residents' proficiency in identifying four specific critical misplacements of medical devices using the Wisdom in Diagnostic Imaging Simulation (WIDI SIM). A retrospective analysis was conducted on 1,102 responses from radiology residents who participated in the WIDI SIM between 2010 and 2022. The majority were first- and second-year residents from multiple institutions. The simulation presented four specific cases featuring misplacements of an endotracheal tube in the esophagus, an intrauterine device embedded in the myometrium, a peripherally inserted central catheter in the right internal jugular vein, and an umbilical venous catheter in the splenic vein. Residents provided free-text interpretations scored on a 0-10 scale by subspecialty radiologists. Errors were categorized as observational (failure to identify misplacement) or interpretive (misinterpretation of identified misplacement). Statistical analyses were performed using Kruskal-Wallis and Dunn's multiple comparisons tests. Across all cases, residents' average scores did not meet the acceptable standard of 7 points. Observational errors were predominant, indicating a failure to recognize these specific device misplacements. Effective report rates were low: 58% for the endotracheal tube case, 35% for the intrauterine device, 19% for the peripherally inserted central catheter, and 25% for the umbilical venous catheter. Significant performance improvements were observed between first- and second-year residents in three of the four cases (p-values ranging from < 0.0001 to 0.0238), but overall proficiency remained suboptimal even among senior residents. This study reveals gaps in radiology residents' ability to identify these specific misplaced lines, tubes, and devices accurately. The consistent pattern of underperformance, primarily due to observational errors, suggests a need for targeted educational interventions to improve resident proficiency in this aspect of emergency radiology.

Near‐field scattering centre modelling for complex targets

AbstractThe parametric scattering centre (SC) model of the target has been widely used in the rapid simulation of radar image. Most of the existing SC models are suitable for far‐field scattering where the radar cross section (RCS) is independent of the distance from the target to the radar. However, when the electromagnetic scattering of the target is in the near‐field region of radiation, the RCS of the target changes dramatically in distance. The existing SC model cannot characterise these important near‐field characteristics. In this paper, the near‐field model with the dependence description of the SC on the distance is proposed. Firstly, the scattering characteristics of several main geometric structures of the extended target in the near‐field radiation region are analysed. Then, on the basis of far‐field SC model expressions, the description of the relationship between amplitude and phase of the SC model and distance is added. Finally, the correctness of the near‐field SC model is verified by comparing with the accurate full‐wave numerical method. In order to further illustrate the practicability of the near‐field SC model, an actual aircraft target is used. The results proved that the near‐field SC model has the advantages of high accuracy and high computational efficiency.

An Image Simulator of Lunar Far-Side Impact Flashes Captured from the Earth-Moon L2 Point

Impact flashes on the moon are caused by high-speed collisions of celestial bodies with the lunar surface. The study of the impacts is critical for exploring the evolutionary history and formation of the Moon, and for quantifying the risk posed by the impacts to future human activity. Although the impacts have been monitored from the Earth by a few projects in past 20 years, the events occurring on the lunar far side have not been explored systematically so far. We here present an end-to-end image simulator dedicated to detecting and monitoring the impacts from space, which is useful for future mission design. The simulator is designed for modularity and developed in the Python environment, which is mainly composed of four components: the flash temporal radiation, the background emission, the telescope and the detector used to collect and measure the radiation. Briefly speaking, with a set of input parameters, the simulator calculates the flash radiation in the context of the spherical droplet model and the background emission from the lunar surface. The resulting images are then generated by the simulator after considering a series observational effects, including the stray light, transmission of the instrument, point spread function and multiple kinds of noise caused by a CCD/CMOS detector. The simulator is validated by comparing the calculation with the observations taken on the ground. The modular design enables the simulator to be improved and enhanced by including more complex physical models in the future, and to be flexible for other future space missions.

Transcranial ultrasound modeling using the spectral-element method.

This work explores techniques for accurately modeling the propagation of ultrasound waves in lossy fluid-solid media, such as within transcranial ultrasound, using the spectral-element method. The objectives of this work are twofold, namely, (1) to present a formulation of the coupled viscoacoustic-viscoelastic wave equation for the spectral-element method in order to incorporate attenuation in both fluid and solid regions and (2) to provide an end-to-end workflow for performing spectral-element simulations in transcranial ultrasound. The matrix-free implementation of this high-order finite-element method is very well-suited for performing waveform-based ultrasound simulations for both transcranial imaging and focused ultrasound treatment thanks to its excellent accuracy, flexibility for dealing with complex geometries, and computational efficiency. The ability to explicitly mesh distinct interfaces between regions with high impedance contrasts eliminates staircasing artifacts, which are otherwise non-trivial to mitigate within discretization approaches based on regular grids. This work demonstrates the efficacy of this modeling technique for transcranial ultrasound through a number of numerical examples. While the examples in this work primarily focus on transcranial applications, this type of modeling is equally relevant within other soft tissue-bone systems such as in limb or spine imaging.

Advancing pure ray tracing for the simulation of volume holographic optical elements: innovations in diffractive waveguide-based augmented reality systems

As augmented reality (AR) glasses technology evolves, volume holographic diffractive waveguide designs are increasingly adopted to enhance portability and performance. Traditionally, these systems require separate geometric and wave optics approaches to handle ray propagation and holographic element diffraction, adding significant complexity to the design process. This study presents an innovative pure ray tracing simulation method that integrates geometric and wave optics seamlessly. By incorporating Kogelnik's coupled wave theory, our model accurately predicts the diffraction behavior of volume holographic optical elements (VHOEs) and converts this information into ray data for tracing, enabling exact AR imaging simulations. Applied to the design of volume holographic waveguide AR glasses, human vision simulations, and experiments validated this method's reliability, demonstrating its versatility and effectiveness. This model improves design efficiency and promotes innovative advancements in cross-theoretical optical system design, positioning it as a crucial tool for future AR glasses development.

Single-Scene SAR Image Data Augmentation Based on SBR and GAN for Target Recognition

High-performance neural networks for synthetic aperture radar (SAR) automatic target recognition (ATR) often encounter the challenge of data scarcity. The lack of sufficient labeled SAR image datasets leads to the consideration of using simulated data to supplement the dataset. On the one hand, electromagnetic computation simulations provide high amplitude accuracy but are inefficient for large-scale datasets due to their complex computations and physical models. On the other hand, ray tracing simulations offer high geometric accuracy and computational efficiency but struggle with low amplitude correctness, hindering accurate numerical feature extraction. Furthermore, the emergence of generative adversarial networks (GANs) provides a way to generate simulated datasets, trying to balance computational efficiency with image quality. Nevertheless, the simulated SAR images generated based on random noise lack constraints, and it is also difficult to generate images that exceed the parameter conditions of the real image’s training set. Hence, it is essential to integrate physics-based simulation techniques into GANs to enhance the generalization ability of the imaging parameters. In this paper, we present the SingleScene-SAR Simulator, an efficient framework for SAR image simulation that operates under limited real SAR data. This simulator integrates rasterized shooting and bouncing rays (SBR) with cycle GAN, effectively achieving both amplitude correctness and geometric accuracy. The simulated images are appropriate for augmenting datasets in target recognition networks. Firstly, the SingleScene-SAR Simulator employs a rasterized SBR algorithm to generate radar cross section (RCS) images of target models. Secondly, a specific training pattern for cycle GAN is established to translate noisy RCS images into simulated SAR images that closely resemble real ones. Finally, these simulated images are utilized for data augmentation. Experimental results based on the constructed dataset show that with only one scene SAR image containing 30 target chips, the SingleScene-SAR Simulator can efficiently produce simulated SAR images that exhibit high similarity in both spatial and statistical distributions compared with real images. By employing simulated SAR images for data augmentation, the accuracy of target recognition networks can be consistently and significantly enhanced.

Multiple-Input Multiple-Output Synthetic Aperture Radar Waveform and Filter Design in the Presence of Uncertain Interference Environment

Multiple-input multiple-output synthetic aperture radar (MIMO-SAR) anti-jamming waveform design relies on accurate prior information about the interference. However, it is difficult to obtain accurate prior knowledge about uncertain intermittent sampling repeater jamming (ISRJ), leading to a severe decline in the detection performance of MIMO-SAR systems. Therefore, this article studies the robust joint design problem of MIMO radar transmit waveform and filter against uncertain ISRJ. We characterize two categories of uncertain interference, including sample length uncertainty and sample-time uncertainty, modeled as Gaussian distribution in different range bins. Based on the uncertain interference model, we formulate the maximizing SINR as a figure of merit, which is a non-convex quadratic optimization problem under specific waveform constraints. Based on the alternating direction method of multipliers (ADMM) framework, a novel joint design algorithm of waveform and filter is proposed. In order to improve the convergence performance of ADMM, the difference in convex functions (DC) programming is applied to the ADMM iterations framework to solve the problem of waveform energy inequality constraint. Finally, numerical results demonstrate the effectiveness and robustness of the proposed method, compared to the existing methods that utilize deterministic interference models in the uncertain ISRJ environment. Moreover, the spaceborne SAR real scene imaging simulations are conducted to evaluate the anti-ISRJ performance.

ECVT imaging and CFD simulation of particle flow in a 90° bend

Gas-solid two-phase flow characteristics in a 90° bend within a pneumatic conveying system are critical for design and performance optimization, impacting conveying efficiency and system safety. Electrical Capacitance Volumetric Tomography (ECVT) and Computational Fluid Dynamics (CFD) simulations were employed in this study to investigate the flow characteristics in the bend. The ECVT system for bends was validated through static tests. A setup with a 36 mm inner diameter was constructed for high-speed 3D imaging of 0.9 mm quartz particles. Flow patterns, solid-phase concentration, particle velocity spectra, and mass flow rate were analyzed under various gas velocities. The Euler-Lagrange method and SST K-ω model were used to simulate particle flow and pipe wall erosion numerically. Results indicate diverse flow patterns across different gas velocities, where moderate turbulence enhances efficiency and limits erosion. This study offers an experimental basis for predicting and controlling particle motion, providing scientific guidance for optimizing pneumatic systems.

Infrared Imaging System with a Local Polarization Channel for Target Detection

Infrared imaging can detect the targets from their backgrounds during the day and night. As a supplementary tool, polarization imaging can visually characterize the polarized information of targets in complicated environments. In this study, an infrared imaging system with a local polarization channel is developed and simulated. The system can acquire local infrared and polarization information of the target without compromising the monitoring of the entire field of view. This system is composed of two infrared imaging channels with a common image plane: a peripheral channel for the entire field of view and a local imaging channel for the target of interest to achieve local magnification and polarization imaging. Herein, an imaging simulation of the infrared imaging system with a local polarization channel is performed, and the results show that the system performs well.

Analysis of Scattering Mechanisms in SAR Image Simulations of Japanese Wooden Buildings Damaged by Earthquake

The difficulty in identifying collapsed houses and damaged structures in synthetic aperture radar (SAR) images after natural disasters represents a significant challenge in the monitoring of urban structural deformation using SAR. SAR image simulation was conducted on a three-dimensional model of a typical wooden building in Japan to analyze the scattering mechanism of the structure in collapsed and uncollapsed states. Based on the physical properties of the buildings, a correlation was established between the simulated SAR image feature signals and the geometric structures of the buildings. The findings indicate that SAR scattering is more uniform for uncollapsed structures, which is predominantly influenced by their geometry. At low incidence angles, single reflections were the predominant phenomenon, whereas at high incidence angles, multiple reflections became more prevalent. The uncollapsed building’s facade formed a dihedral angle, exhibiting bright lines in the SAR image. Multiple reflections occurred at the edges of the building and floor junctions. These findings follow the theoretical predictions. In the case of the collapsed buildings, multiple reflections occurred with greater frequency, and irregular scattering was observed. Notwithstanding the augmented scattering pathways, some walls nevertheless manifested single reflections. The collapsed structures demonstrated a reduced sensitivity to alterations in the angle of incidence.

Dose-efficient phase-contrast imaging of thick weak phase objects via OBF STEM using a pixelated detector.

Optimum bright-field scanning transmission electron microscopy (OBF STEM) is a recently developed low-dose imaging technique that uses a segmented or pixelated detector. While we previously reported that OBF STEM with a segmented detector has a higher efficiency than conventional STEM techniques such as annular bright field (ABF), the imaging efficiency is expected to be further improved by using a pixelated detector. In this study, we adopted a pixelated detector for the OBF technique and investigated the imaging characteristics. Because OBF imaging is based on the thick weak phase object approximation (tWPOA), a non-zero crystalline sample thickness is considered in addition to the conventional WPOA, where the pixelated OBF method can be regarded as the theoretical extension of single side band (SSB) ptychography. Thus, we compared these two techniques via signal-to-noise ratio transfer functions (SNRTFs), multi-slice image simulations, and experiments, showing how the OBF technique can improve dose efficiency from the conventional WPOA-based ptychographic imaging.

Unveiling mechanisms and onset threshold of humping in high-speed laser welding

The fabrication of fuel cells relies on a rapid laser welding process. However, challenges arise with the occurrence of humping when the welding speed surpasses a critical threshold, which poses difficulties in achieving a smooth surface finish and a consistent weld strength. This study aims to elucidate the humping mechanisms by analyzing the morphology of molten pool and the characteristics of melt flow at varying welding speeds via in situ synchrotron high-speed X-ray imaging and computational fluid dynamics simulations. Our findings indicate that the short keyhole rear wall, the high backward melt velocity, and the prolonged tail of molten pool are the primary factors contributing to the onset of humping. Furthermore, a dimensionless humping index (πh\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\pi }_{h}$$\\end{document}) was introduced, which successfully captured the onset threshold of humping across different literatures. This index not only provides a quantitative description of the humping formation tendency but also serves as a valuable tool for optimizing the laser welding process.

Probing rapid solidification pathways in refractory complex concentrated alloys via multimodal synchrotron X-ray imaging and melt pool-scale simulation

AbstractRefractory complex concentrated alloys (RCCAs) show potential as the next-generation structural materials due to their superior strength in extreme environments. However, RCCAs processed by metal additive manufacturing (AM) typically suffer from process-related challenges surrounding laser material interaction defects and microstructure control. Multimodal in situ techniques (synchrotron X-ray imaging and diffraction and infrared imaging) and melt pool-level simulations were employed to understand rapid solidification pathways in two representative RCCAs: (i) multi-phase BCC + HCP Ti0.4Zr0.4Nb0.1Ta0.1 and (ii) single-phase BCC Ti0.486V0.375Cr0.111Ta0.028. As expected, laser material interaction defects followed similar systematic trends in process parameter space for both alloys. Additionally, both alloys formed a single-phase (BCC) microstructure after rapid solidification processing. However, significant differences in microstructure selection between these alloys were discovered, where Ti0.4Zr0.4Nb0.1Ta0.1 showed a mixture of equiaxed and columnar grains, while Ti0.486V0.375Cr0.111Ta0.028 was dominated by columnar growth. These behaviors were well described by the influence of undercooling effects on columnar-to-equiaxed transition (CET). Distinct microstructure formation in each alloy was verified through CET predictions via analytical melt pool simulations, which showed a ~ 5 × increase degrees in undercooling for Ti0.4Zr0.4Nb0.1Ta0.1 compared to Ti0.486V0.375Cr0.111Ta0.028. Overall, these results show that microstructure control based on modulating the freezing range must be balanced with process considerations which resist defect formation, such as solidification crack formation in RCCAs. Graphical abstract

Single-molecule imaging and molecular dynamics simulations reveal early activation of the MET receptor in cells

Embedding of cell-surface receptors into a membrane defines their dynamics but also complicates experimental characterization of their signaling complexes. The hepatocyte growth factor receptor MET is a receptor tyrosine kinase involved in cellular processes such as proliferation, migration, and survival. It is also targeted by the pathogen Listeria monocytogenes, whose invasion protein, internalin B (InlB), binds to MET, forming a signaling dimer that triggers pathogen internalization. Here we use an integrative structural biology approach, combining molecular dynamics simulations and single-molecule Förster resonance energy transfer (smFRET) in cells, to investigate the early stages of MET activation. Our simulations show that InlB binding stabilizes MET in a conformation that promotes dimer formation. smFRET reveals that the in situ dimer structure closely resembles one of two previously published crystal structures, though with key differences. This study refines our understanding of MET activation and provides a methodological framework for studying other plasma membrane receptors.

Cryo-EM phase-plate images reveal unexpected levels of apparent specimen damage

Apoferritin (apoF) is commonly used as a test specimen in single-particle electron cryo-microscopy (cryo-EM), since it consistently produces density maps that go to 3 Å resolution or higher. When we imaged apoF with a laser phase plate (LPP), however, we observed more severe particle-to-particle variation in the images than we had previously thought to exist. Similarly, we found that images of ribulose bisphosphate carboxylase/oxygenase (rubisco) also exhibited a much greater amount of heterogeneity than expected. By comparison to simulations of images, we verified that the heterogeneity is not explained by the known features of the LPP, shot noise, or differences in particle orientation. We also demonstrate that our specimens are comparable to those previously used in the literature, based on using the final-reconstruction resolution as the metric for evaluation. All of this leads us to the hypothesis that the heterogeneity is due to damage that has occurred either during purification of the specimen or during preparation of the grids. It is not, however, our goal to explain the causes of heterogeneity; rather, we report that using the LPP has made the apparent damage too obvious to be ignored. In hindsight, similar heterogeneity can be seen in images of apoF and the 20S proteasome which others had recorded with a Volta phase plate. We therefore conclude that the increased contrast of phase-plate images (at low spatial frequencies) should also make it possible to visualize, on a single-particle basis, various forms of biologically functional heterogeneity in structure that had previously gone unnoticed.

Imaging simulation analysis of space targets by different observed orbits

Abstract For most optical simulations of space targets, static imaging characteristics are studied with a pre-set angle and attitude which are less consistent with the actual situation for satellite detectors’ dynamic image. Especially when the detector and the target are in different orbits, the imaging angles and attitudes also vary. In this article, two kinds of observed orbits are selected to simulate the detector image results, and the observed attitude and angle are updated over time through the simulation process. Furthermore, a temperature field of the space target is also calculated as preconditioned data to be taken into account in the optical simulation, instead of roughly estimating the temperature. The result of the study reveals that when the satellite detector and target operate at coplanar orbits, closer distances (ranging from 236 km to 28 km) allow for the acquisition of more specific details regarding the target’s characteristics. This research may offer a new approach to selecting orbits to obtain high-quality imaging data.

Detecting the near-infrared afterglows of high-redshift gamma-ray bursts using CAGIRE

Transient sky astronomy is entering a new era with the advent of the Space Variable Objects Monitor mission (SVOM), successfully launched on 22 June 2024. The primary goal of SVOM is to monitor the hard X-ray sky searching for gamma-ray bursts (GRBs). On top of its on-board follow-up capabilities, SVOM will be backed by its ground segment composed of several facilities, including the near-infrared (NIR) imager CAGIRE. Mounted on the robotic telescope COLIBRI, it will be a unique instrument capable of performing fast follow-up of GRB afterglows in the J and H bands, ideal for capturing high-redshift (z$&gt;$6) and/or obscured GRBs. This paper is aimed at estimating the performances of CAGIRE for GRB NIR afterglow detection based on the characteristics of the detector and the specificities of the COLIBRI telescope. Quickly fading GRB afterglows pose challenges that should be addressed by adapting observing strategies to the capabilities of CAGIRE. We used an end-to-end image simulator to produce realistic CAGIRE images, taking into account the results from the characterisation of the ALFA detector used by CAGIRE. We implemented a GRB afterglow generator that simulates infrared light curves and spectra based on published observation of distant GRBs (z$&gt;$6). We retrieved the photometry of nine GRB afterglows in various scenarios covered by CAGIRE. Capturing afterglows as early as one minutes after the burst allows for the identification of a NIR counterpart in the brightest four events. When artificially redshifted even further away, these events remain detectable by CAGIRE up to z=9.6 in the J band and z=13.3 in H band, indicating the pioneering potential of CAGIRE in identifying the most distant GRBs to date.

Research on the Laser Scattering Characteristics of Three-Dimensional Imaging Based on Electro-Optical Crystal Modulation.

In this paper, we construct a laser 3D imaging simulation model based on the 3D imaging principle of electro-optical crystal modulation. Unlike the traditional 3D imaging simulation method, this paper focuses on the laser scattering characteristics of the target scene. To accurately analyze and simulate the scattering characteristic model of the target under laser irradiation, we propose a BRDF (Bidirectional Reflectance Distribution Function) model fitting algorithm based on the hybrid BBO-Firefly model, which can accurately simulate the laser scattering distribution of the target at different angles. Finally, according to the fitted scattering characteristic model, we inverted the target imaging gray map. We used the laser 3D imaging restoration principle to reconstruct the 3D point cloud of the target to realize the laser 3D imaging of the target.

Computer simulation of x-ray section topography of gas pores in a silicon carbide crystal

The results of computer simulation of images of gas pores in a silicon carbide crystal in sectional topograms, that is, during diffraction of a narrow beam of X-rays in the crystal, are presented for the first time. For this purpose, a special module of the universal computer program XRWP was used. This program is developing by the author to calculate the effects of coherent X-ray optics. The calculation method combines two methods, previously known, namely, Fourier transform methods (Kato method), and the method of solving the Takagi-Taupin equations. It is shown that gas pores can produce a wide variety of images, depending on the experimental conditions and the position of the gas pore inside the crystal.

On-Orbit Geometric Calibration and Accuracy Validation of the Jilin1-KF01B Wide-Field Camera

On-orbit geometric calibration is key to improving the geometric positioning accuracy of high-resolution optical remote sensing satellite data. Grouped calibration with geometric consistency (GCGC) is proposed in this paper for the Jilin1-KF01B satellite, which is the world’s first satellite capable of providing 150-km swath width and 0.5-m resolution data. To ensure the geometric accuracy of high-resolution image data, the GCGC method conducts grouped calibration of the time delay integration charge-coupled device (TDI CCD). Each group independently calibrates the exterior orientation elements to address the multi-time synchronization issues between imaging processing system (IPS). An additional inter-chip geometric positioning consistency constraint is used to enhance geometric positioning consistency in the overlapping areas between adjacent CCDs. By combining image simulation techniques associated with spectral bands, the calibrated panchromatic data are used to generate simulated multispectral reference band image as control data, thereby enhancing the geometric alignment consistency between panchromatic and multispectral data. Experimental results show that the average seamless stitching accuracy of the basic products after calibration is better than 0.6 pixels, the positioning accuracy without ground control points(GCPs) is better than 20 m, the band-to-band registration accuracy is better than 0.3 pixels, the average geometric alignment consistency between panchromatic and multispectral data are better than 0.25 multispectral pixels, the geometric accuracy with GCPs is better than 2.1 m, and the geometric alignment consistency accuracy of multi-temporal data are better than 2 m. The GCGC method significantly improves the quality of image data from the Jilin1-KF01B satellite and provide important references and practical experience for the geometric calibration of other large-swath high-resolution remote sensing satellites.