- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Contrast enhanced tomographic reconstruction of vascular blood flow with first order and second order adjoint methods
摘要： In this work, we study the reconstruction of blood velocity with contrast enhanced computed tomography with a tomographic projections perpendicular to the main flow field direction. The inverse problem is regularized with a convection-diffusion partial differential equation. The velocity field is reconstructed with first order and second order adjoint methods with a receding optimal control method and tested on simple phantoms.
关键词： optimal control,tomography,X-ray imaging,Inverse problems
更新于2025-09-11 14:15:04
-
On-the-Fly Fast X-Ray Tomography Using a CdTe Pixelated Detector – Application in Mechanical Testing
摘要： Fast tomography measurements are still done almost exclusively within the domain of synchrotrons. However, recent progress in X-ray imaging instrumentation has enabled researchers to perform time-lapse computed tomography (4D-CT) even under laboratory conditions with standard X-Ray sources. Thus, fast time-dependent processes within materials with relatively high X-Ray attenuation can be monitored. The article describes the in-situ tomographic monitoring of crack formation and propagation in a quasi-brittle silicate matrix composite subjected to three point bending. A three-dimensional CT volume containing the region of interest (ROI) in the specimen is imaged over a period of time while the continuously increasing load causes crack initiation and propagation, creating a dynamic volume dataset. An acquisition time of 50 seconds for one full angle tomography with 400 projections makes this tomographic system one of the fastest systems in the world. The resulting visualizations provide qualitative information concerning progressive crack propagation within areas of lower material density. Differential images then allow displaying the spatial orientation of the crack over time. The results were further processed for a quantitative analysis of image quality using various methods of beam hardening correction.
关键词： X-ray imaging techniques,X-ray tomography,Materials characterization,Mechanical testing,Quasi-brittle material,Fracture mechanics,CdTe detectors
更新于2025-09-10 09:29:36
-
Gain depletion of X-ray framing camera
摘要： X-ray imaging is very useful to investigate imploded core plasma in inertial fusion experiments. We can obtain information from X-ray images, such as shape, density, and temperature. An X-ray framing camera (XFC) capable of taking two-dimensional, time-resolved X-ray images is used to capture the images. In previous work, we developed a numerical model of an XFC to analyze its X-ray image. The calculated results agreed qualitatively with experimental results. However, it was not accurate enough to determine the absolute value of the signal. We thought this discrepancy was caused by gain depletion. In high energy laser experiments, high photon flux may cause gain depletion. This is a problem for accurate X-ray measurement. In this paper, we report our new model, including gain depletion. The new model is evaluated by tabletop laser experiments and high energy laser experiments. The results calculated using the new model agree quantitatively with our experimental results. Furthermore, we confirmed that gain depletion occurs in our high energy laser experiments. For quantitatively accurate X-ray intensity measurements, the XFC should be used with limited incident photon flux such that the gain linearity is guaranteed.
关键词： inertial fusion experiments,X-ray imaging,gain depletion,X-ray framing camera
更新于2025-09-10 09:29:36
-
SoilJ: An ImageJ Plugin for the Semiautomatic Processing of Three-Dimensional X-ray Images of Soils
摘要： Noninvasive three- and four-dimensional X-ray imaging approaches have proved to be valuable analysis tools for vadose zone research. One of the main bottlenecks for applying X-ray imaging to data sets with a large number of soil samples is the relatively large amount of time and expertise needed to extract quantitative data from the respective images. SoilJ is a plugin for the free and open imaging software ImageJ that aims at automating the corresponding processing steps for cylindrical soil columns. It includes modules for automatic column outline recognition, correction of image intensity bias, image segmentation, extraction of particulate organic matter and roots, soil surface topography detection, as well as morphology and percolation analyses. In this study, the functionality and precision of some key SoilJ features were demonstrated on five different image data sets of soils. SoilJ has proved to be useful for strongly decreasing the amount of time required for image processing of large image data sets. At the same time, it allows researchers with little experience in image processing to make use of X-ray imaging methods. The SoilJ source code is freely available and may be modified and extended at will by its users. It is intended to stimulate further community-driven development of this software.
关键词： ImageJ plugin,image processing,SoilJ,3-D X-ray imaging,vadose zone research
更新于2025-09-10 09:29:36
-
Bending characteristic analysis and improvement of fusion splice between photonic crystal fiber and single mode fiber
摘要： We report a study of bending characteristic analysis and improvement of fusion splice between the photonic crystal fiber (PCF) and the single mode fiber (SMF). The poor bending characteristic of the splice between the PCF and the SMF is a threat to the fiber optic gyroscope (FOG). However, the tensile strength test shows that the splice should be able to withstand a much smaller bending radius. To solve this problem, we adopt three-dimensional (3D) X-Ray imaging to acquire the accurate structure of the splice and conclude that the stress concentration leads to the poor bending characteristic of the splice. A simple fiber tapering method is proposed to improve the bending characteristic of the splice without compromising the splice loss. The improved splice method for PCF has been used in FOG for space application successfully.
关键词： photonic crystal fiber,X-ray imaging,Bending characteristic,fiber splicing,fiber tapering
更新于2025-09-10 09:29:36
-
Two-channel high-resolution quasi-monochromatic X-ray imager for Al and Ti plasma
摘要： High-resolution, high-sensitivity X-ray imaging is a real challenge in high-energy density plasma experiments. We present an improved design of the Fresnel ultra high-resolution imager instrument. Using an Ultra-High-Intensity (UHI) laser to generate hot and dense plasma in a small volume of an Al-Ti mixed target provides simultaneous imaging of both Al and Ti X-ray emission. Specifically, the Al Heβ (or Lyβ) and the Ti Heα lines are imaged with a resolution of (2.7 ± 0.3) μm and (5.5 ± 0.3) μm, respectively. It features two transmission Fresnel phase zone plates fabricated on the same substrate, each associated with a multilayer mirror for spectral selection. Their spatial resolution has been measured on the PTB synchrotron radiation facility laboratory at BESSY II and on the EQUINOX laser facility. Results obtained on an UHI experiment highlight the difference of emission zone sizes between Al and Ti lines and the versatility of this instrument.
关键词： plasma experiments,Fresnel zone plates,multilayer mirrors,high-resolution,X-ray imaging
更新于2025-09-10 09:29:36
-
High-precision compton imaging of 4.4 MeV prompt gamma-ray toward an on-line monitor for proton therapy
摘要： Proton therapy is a widely used and effective treatment for cancer. A high-dose concentration of proton beam reduces damage to normal tissues. However, it also requires a high accuracy of irradiation. PET is generally used to verify the proton range after irradiation, but, the distributions of positrons and the energy deposited by protons are not similar to each other. Recently, prompt gamma-ray imaging has attracted attention as a new, online imaging technique. In particular, 4.4 MeV gamma ray emitted from 12C* is one of the best probes to monitor the proton dose, however imaging techniques are far from established. We have developed a novel, 3-D position sensitive Compton camera based on Ce:GAGG scintillators coupled with multi-pixel photon counter (MPPC) arrays, thus making it optimized for imaging in the 1-10 MeV range. The angular resolution is 5 degrees (FWHM) at 4.4 MeV. We have established various methods to discriminate multiple-Compton and escape events, both of which can be critical backgrounds for precise imaging of prompt gamma rays. By irradiating a 70 MeV proton beam on the PMMA phantom, we demonstrated that 4.4 MeV gamma ray image is sharply concentrated on the Bragg peak, as was expected from the PHITS simulation.
关键词： proton therapy,MPPC,prompt gamma-ray imaging,Compton camera
更新于2025-09-09 09:28:46
-
[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Backscatter Radiography as a Non-Destructive Examination Tool for Concrete Structures
摘要： Concrete is widely used in different applications like bridges, tunnels, railroad crossties, etc. Assessing the damage and replacing these concrete structures in the early stages is crucial to prevent any catastrophic events. The x-ray backscatter imaging has the advantage of being single-sided imaging technique, which can be used for the non-destructive examination of the concrete structures. The x-ray radiography by selective detection and the x-ray fan beam radiography systems at the University of Florida were used for testing and comparison in order to develop an efficient and a high-resolution x-ray backscatter imaging system. GEANT4 was also used to simulate and study the feasibility of a high-speed rotating pencil beam radiography system. The backscatter images of different concrete contrast tools were produced and analyzed in this paper.
关键词： x-ray imaging,non-destructive examination,backscatter radiography,concrete structures,GEANT4 simulations
更新于2025-09-09 09:28:46
-
On evaluating x-ray imaging crystals with synchrotron radiation
摘要： Bent crystals used in diagnostics of plasmas combine x-rays diffracted from across the crystal. Therefore imperfections in the resulting 1-D spectrum or 2-D image are not the best way to find out why one particular crystal may differ in its performance from another and what, if anything, to do about it. Instead, here we want to measure the diffraction locally, with the necessary resolution. Nominally monochromatic and unidirectional radiation from the synchrotron’s standard x-ray optics proved to be insufficient for the purpose. Here much better radiation comes from the x-ray topography setup at the x-ray optics testing beamline 1-BM at the Advanced Photon Source, thanks to a specially designed quartz conditioning crystal. Some worrisome features in a bent crystal’s diffraction have thereby disappeared, while minor fabrication flaws remain highly visible.
关键词： x-ray imaging,diffraction,synchrotron radiation,plasma diagnostics,bent crystals
更新于2025-09-09 09:28:46
-
Effect of CsI(Tl) micro-conical-frustums on the performance of the pixelated CsI(Tl) scintillation screen in X-ray imaging
摘要： The pixelated CsI(Tl) scintillation screen based on oxidized silicon micro-pore array template with CsI(Tl) micro-conical-frustums (CMCF) was proposed. The effect of the CMCF on the performance of the pixelated CsI(Tl) scintillation screen in X-ray imaging was studied by using Geant4 Monte Carlo simulation code. The variations of the light output (LO), modulation transfer function (MTF) and detective quantum efficiency (DQE) for the screen with the cone angle β of the CMCF in X-ray imaging were revealed. The results show that the LO of the pixelated scintillation screen with CMCF is superior to that of the screens with CsI(Tl) micro-cylinders (CMC) or with reversed CsI(Tl) micro-conical-frustums (RCMCF), but the spatial resolution of the X-ray imaging system by using the pixelated scintillation screen with RCMCF is better than that by using the screens with CMCF or with CMC. At low frequency, the cone angle β corresponding to DQEs from good to bad are 2.40°, 0.00° and -2.40°. But at high frequency, the cone angle β corresponding to DQEs from good to bad change to 2.40°, -2.40° and 0.00°. The reason is that, for a pixelated scintillation screen, the DQE for the screen not only depends on the efficiency of X-ray absorption, but also depends on the number of scintillation photons exiting the bottom the screen per interacting X-ray photon and its Poisson excess, and MTF. The simulated results of DQEs show that the comprehensive performance of the pixelated CsI(Tl) screen with CMCF in X-ray imaging is better than that of the screens with CMC or with CRMCF.
关键词： Shape of CsI(Tl) micro-conical-frustum,Performance in X-ray imaging,Oxidized silicon micro-pore array template,Pixelated CsI(Tl) scintillation screen
更新于2025-09-09 09:28:46