Imaging Detector Research Articles

A new thermography using inelastic scattering analysis of wavelength-resolved neutron transmission imaging

Thermography using energy-dependent neutron transmission imaging can non-invasively and non-destructively visualize a real-space distribution of interior temperatures of a material in a container. Previously, resonance absorption broadening analysis and Bragg-edge shift analysis using energy-resolved neutron transmission have been developed, however some issues remain, e.g., imaging efficiency, substance limitation and temperature sensitivity. For this reason, we propose a new neutron thermography using the temperature dependence of inelastic scattering of cold neutrons. This method has some advantages, for example, the imaging efficiency is high because cold neutrons are measured with moderate wavelength resolution, and light elements can be analysed in principle. We investigated the feasibility of this new neutron thermography at pulsed neutron time-of-flight imaging instruments at ISIS in the United Kingdom and HUNS in Japan. A Rietveld-type transmission spectrum analysis program (RITS) was employed to refine temperature and atomic displacement parameters from the inelastic scattering cross-section analysis. Finally, we demonstrated interior thermography of an α-Fe sample of 10 mm thickness inside a vacuum chamber by using a neutron time-of-flight imaging detector at the compact accelerator-driven pulsed neutron source HUNS.

Analysis of a convex time skew calibration for light sharing-based PET detectors

Objective. Positron emission tomography (PET) detectors providing attractive coincidence time resolutions (CTRs) offer time-of-flight information, resulting in an improved signal-to-noise ratio of the PET image. In applications with photosensor arrays that employ timestampers for individual channels, timestamps typically are not time synchronized, introducing time skews due to different signal pathways. The scintillator topology and transportation of the scintillation light might provoke further skews. If not accounted for these effects, the achievable CTR deteriorates. We studied a convex timing calibration based on a matrix equation. In this work, we extended the calibration concept to arbitrary structures targeting different aspects of the time skews and focusing on optimizing the CTR performance for detector characterization. The radiation source distribution, the stability of the estimations, and the energy dependence of calibration data are subject to the analysis. Approach. A coincidence setup, equipped with a semi-monolithic detector comprising 8 LYSO slabs, each 3.9 mm × 31.9 mm × 19.0 mm, and a one-to-one coupled detector with 8 × 8 LYSO segments of 3.9 mm × 3.9 mm × 19.0 mm volume is used. Both scintillators utilize a dSiPM (DPC3200-22-44, Philips Digital Photon Counting) operated in first photon trigger. The calibration was also conducted with solely one-to-one coupled detectors and extrapolated for a slab-only setup. Main results. All analyzed hyperparameters show a strong influence on the calibration. Using multiple radiation positions improved the skew estimation. The statistical significance of the calibration dataset and the utilized energy window was of great importance. Compared to a one-to-one coupled detector pair achieving CTRs of 224 ps the slab detector configuration reached CTRs down to 222 ps, demonstrating that slabs can compete with a clinically used segmented detector design. Significance. This is the first work that systematically studies the influence of hyperparameters on skew estimation and proposes an extension to arbitrary calibration structures (e.g. scintillator volumes) of a known calibration technique.

透射电子显微镜空间分辨率综述

Transmission electron microscope (TEM) is one of the most important research tools in a wide range of research fields such as chemistry, materials science, physics, and biological science. There are many factors affect the spatial resolution of TEM, including not only the construction of electron microscope and imaging mechanism, but also the nature of the sample and other reasons. In order to systematically and comprehensively understand the meaning, principle and application of TEM spatial resolution, this paper firstly briefly describes the history of TEM spatial resolution advancement, and then theoretically clarifies the concept, physical meaning, influencing factors and application scope of TEM spatial resolution, then outlines the influence of TEM electron gun, magnetic lens, image detector and internal and external environment on the resolution, the development of monochromator, aberration corrector and new image detector from the perspective of electron microscope device. Finally, from the perspective of practical applications, the mechanism of resolution degradation due to thickness, electron beam sensitivity, carbon accumulation and atomic vibrations and the corresponding solutions are highlighted.

Quantum state and detector tomography with known rank

Quantum state tomography and quantum detector tomography are two main problems in quantum system identification. In this paper, we study state tomography and detector tomography with prior knowledge about the true rank of the unknown state/detector. In this case, we propose a sufficient condition for static (non-adaptive) tomography algorithms to achieve the optimal infidelity scaling O(1/N) on the number of state copies N. Then we present two examples of such static quantum state tomography and quantum detector tomography algorithms. Numerical examples demonstrate the effectiveness of our algorithms.

Noncontact Respiratory Motion Detection in Anesthetized Rodents

Small animal physiology studies are often complicated, but the level of complexity is greatly increased when performinglive-animal X-ray imaging studies at synchrotron radiation facilities. This is because these facilities are typically not designedspecifically for biomedical research, and the animals and image detectors are located away from the researchers in a radiationenclosure. In respiratory X-ray imaging studies one challenge is the detection of respiration in free-breathing anaesthetisedrodents, to enable images to be acquired at specific phases of the breath and for detecting changes in respiratory rate. Wehave previously used a Philtec RC60 sensor interfaced to a PowerLab data acquisition system and custom-designed timinghub to perform this task. Here we evaluated the Panasonic HL-G108 for respiratory sensing. The performance of the twosensors for accurate and reliable breath detection was directly compared using a single anesthetized rat. We also assessedhow an infrared heat lamp used to maintain body temperature affected sensor performance. Based on positive results fromthese comparisons, the HL-G108 sensor was then used for respiratory motion detection in tracheal X-ray imaging studies of21 rats at the SPring-8 Synchrotron, including its use for gated image acquisition. The results of that test were compared toa similar imaging study that used the RC60 for respiratory detection in 19 rats. Finally, the HL-G108 sensor was tested on 5mice to determine its effectiveness on smaller species. The results showed that the HL-G108 is much more robust and easierto configure than the RC60 sensor and produces an analog signal that is amenable to stable peak detection. Furthermore,gated image acquisition produced sequences with substantially reduced motion artefacts, enabling the additional benefit ofreduced radiation dose through the application of shuttering. Finally, the mouse experiments showed that the HL-G108 isequally capable of detecting respiration in this smaller species.

Noncontact Respiratory Motion Detection in Anesthetized Rodents

Small animal physiology studies are often complicated, but the level of complexity is greatly increased when performinglive-animal X-ray imaging studies at synchrotron radiation facilities. This is because these facilities are typically not designedspecifically for biomedical research, and the animals and image detectors are located away from the researchers in a radiationenclosure. In respiratory X-ray imaging studies one challenge is the detection of respiration in free-breathing anaesthetisedrodents, to enable images to be acquired at specific phases of the breath and for detecting changes in respiratory rate. Wehave previously used a Philtec RC60 sensor interfaced to a PowerLab data acquisition system and custom-designed timinghub to perform this task. Here we evaluated the Panasonic HL-G108 for respiratory sensing. The performance of the twosensors for accurate and reliable breath detection was directly compared using a single anesthetized rat. We also assessedhow an infrared heat lamp used to maintain body temperature affected sensor performance. Based on positive results fromthese comparisons, the HL-G108 sensor was then used for respiratory motion detection in tracheal X-ray imaging studies of21 rats at the SPring-8 Synchrotron, including its use for gated image acquisition. The results of that test were compared toa similar imaging study that used the RC60 for respiratory detection in 19 rats. Finally, the HL-G108 sensor was tested on 5mice to determine its effectiveness on smaller species. The results showed that the HL-G108 is much more robust and easierto configure than the RC60 sensor and produces an analog signal that is amenable to stable peak detection. Furthermore,gated image acquisition produced sequences with substantially reduced motion artefacts, enabling the additional benefit ofreduced radiation dose through the application of shuttering. Finally, the mouse experiments showed that the HL-G108 isequally capable of detecting respiration in this smaller species.

Colloidal KLu3F10:Tb3+ persistent luminescence nanocrystal based flexible detectors for 3D X-ray imaging

Colloidal KLu3F10:Tb3+ persistent luminescence NCs have been synthesized through a simple hydrothermal method, and exhibit excellent flexibility and high sensitivity for X-ray detection and imaging applications.

Characterization of 3D micro-structured TIMEPIX detectors for neutron imaging

Neutron imaging provides additional information to X-ray imaging and can be used in many applications, for example, nuclear engineering, non-industrial diagnostics and homeland security. This paper presents the latest development results of a new 3D structured pixel detector for thermal neutron detection and imaging. The device is based on Medipix/Timepix read-out chip family. The detector, without converter materials, was initially tested in the laboratory with a 241Am source, to simulate events that are induced by reaction products of active material in the silicon bulk. Thanks to the analysis of the size of event clusters and deposited energy, α particles and noise signals were discriminated. The detector was also tested with β and γ sources, to study the effect of other radiation on the device. These results can be useful as a starting point for future experiments, where a neutron source will be used, after filling the cavities with active materials, such as 6Li or 10B. In this paper, the results of the characterization and a comparison between experimental data and Monte Carlo simulations are shown.

Suspicious Object Detection for Millimeter-Wave Images with Multi-View Fusion Siamese Network.

Millimeter-wave (MMW) imaging techniques have been widely used in the public security industries for their under-controlled privacy concerns and no health hazards. However, since MMW images are low resolution and most objects are small, reflection-weak, diverse, suspicious object detection in the MMW images is a very challenging task. This paper develops a robust suspicious object detector for the MMW images based on the Siamese network integrated with the pose estimation and image segmentation, which estimates the coordinates of human joints and segments the complete human images into symmetrical body part images. Unlike most existing detectors, which detect and recognize suspicious objects in MMW images and require a complete training set with correct annotations, our proposed model aims to learn the similarity between two symmetrical human body part images segmented from the complete MMW images. Furthermore, to decrease the misdetection caused by the restricted field of view, we further fuse the multi-view MMW images observed from the same person by designing a decision-level fusion strategy and feature-level fusion strategy based on the attention mechanism. Experimental results on the measured MMW images show that our proposed models have favorable detection accuracy and speed in practical application and thus prove their effectiveness.

Seeing radioactivity: Gamma-ray imaging technique applied to TRIGA RC-1 Research Reactor in ENEA Casaccia

Current radiological characterization protocols applied in nuclear installations provide a valuable set of information used to assess level and distribution of radioactivity, which is a crucial information in the plant management. Nevertheless, typical routines may present limitations that novel technologies can alleviate. In this work, a new-generation 3D pixelated CdZnTe gamma imaging and spectrometer detector has been used at TRIGA RC-1 Research Reactor in ENEA Casaccia Research Centre to assess its performances in several possible tasks and effectively understand this technology readiness. In particular, three possible tasks have been considered: survey of potentially contaminated area (with determination of known and unknown hot spots), source identification and localization (including neutron sources via their gamma emissions), and quantification of isotope-specific activities in generic components thanks to the point-kernel-based algorithm the system is equipped with. The experience has demonstrated the capability to achieve reliable results in these tasks, with consequences that could impact not only the current characterization protocols but also the way some Nuclear Safeguards and Non-Proliferation operations are performed.

Timing, Energy, and 3-D Spatial Resolution of the BING PET Detector Module.

We evaluated the 3D spatial, energy, and timing resolution of the Brain (or Breast)-Initiative Next-Generation (BING) PET detector. The BING detector is an array of 1-mm-thick slats of LYSO scintillator with lapped specular-reflective faces (15-mm by 52-mm) that are stacked together and oriented with their long-narrow edges normal to the imaging field of view. Interaction positions are determined from the signals of silicon-photomultiplier (SiPM) arrays placed on the entrance (top) and exit (bottom) faces. The SiPM arrays are offset to determine the slat of interaction (SOI) without requiring any optical light sharing between slats. Maximum likelihood 2D location within the SOI is determined using the sensor signals. Interaction time is determined with a modified first-optical-photon pickoff method. Performance of the BING detector was measured as a function of position using a sideways coincidence-collimated beam. Slats were accurately identified, with an effective tangential detector resolution of 1 mm. Average resolutions (and ranges) are: 0.96 mm (0.85 mm to 1.11 mm) for lateral (axial) detector resolution, 1.6 mm (1.0 mm to 2.1 mm) for depth resolution, 13.6% (12.7% to 16.0%) for energy resolution, and 317 ps (241 ps to 404 ps) for coincidence timing resolution. Initial spatial and timing resolution results demonstrated that the BING detector can be effective in a small field-of view (e.g., brain or breast) PET system.

An FPGA Charge-to-Digital Converter Based on Voltage-Referenced Receivers for PET Applications

A field programmable gate array (FPGA) voltage-referenced standard receiver based charge-to-digital converter (QDC) was proposed. The QDC is based on a linear discharge scheme. In the linear discharge circuit, typically, a low-voltage differential signaling (LVDS) receiver serves as a voltage comparator. Our proposed scheme takes advantage of voltage-referenced standard in the FPGA instead of the LVDS standard, which maximizes the capability of multichannel and multifunctionality. The linearity differences were compared between the voltage-referenced receivers and the LVDS receiver. To validate the scheme for radiation detector application, a 32-channel electronics prototype based on the proposed structure was developed. A positron emission tomography (PET) detector module was built. The detector is made up of a 15 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 15 LYSO array directly coupled with two silicon photomultipliers (SiPM) at two ends. The mean energy resolution for single crystal at the center can reach 17.9%. The linear discharge scheme based on voltage-referenced receivers provides a promising method for a compact, multichannel electronics readout system for radiation detector application.

Position linearity analysis of circular arc terminated resistive anode using finite element method for photon-counting imaging detectors.

This study proposes a comprehensive model of the circular arc terminated (CAT) resistive anode based on the finite element method to explore the dynamic process of charge diffusion on this anode and its position linearity performance. The waveforms of charges of the electrodes on the anode are calculated for different electrical parameters and their influence on positional linearity is investigated. The influence of the signal development time and the non-uniformity of the resistance per square of the anode on positional linearity is also analyzed. The results of simulations show that the non-linearity of the image varies monotonically with the termination resistance and the non-uniformity of the resistance per square of the anode, but has a non-linear relationship with the signal development time and the ratio of the resistance per square. A CAT resistive anode with capacitance c and a resistance per square of the sensitive area of R▱ can be used to recover an image with a root mean-squared non-linearity of 2%, when the charge signals of the electrode are collected for at least 0.6R▱c s. The reliability of the results of the simulations was verified with experimental measurements.

Characterization of 3.2 Gbps readout in 65 nm CMOS technology

A new class of photon-counting pixel detectors allows for capturing of an image in several photon energy bins in one shot. A decreased pixel pitch and an increased number of energy bins are needed to enhance the spatial and spectral resolution of the detector. This led to new requirements for the readout systems and their bandwidths, as more data is generated for the same detection area. Fast differential serial communication enables high-speed data rates, thus providing an ideal solution to transfer large amounts of data generated by the detector’s front-end electronics. However, its implementation provides extra challenges. This work introduces a novel high-speed serial readout designed in a 65 nm CMOS technology that will be used in the future photon-counting X-ray imaging detectors. The design of the serial transmitter is presented together with the characterization of jitter and channel performance.

In Vivo Measurement of Cerebral SPIO Concentration in Nonhuman Primate Using Magnetic Particle Imaging Detector

<i>In Vivo</i> Measurement of Cerebral SPIO Concentration in Nonhuman Primate Using Magnetic Particle Imaging Detector

Plasma in-situ imaging detection technology on China’s Space Station Wentian module

&lt;sec&gt;In order to meet the needs of ionospheric research and monitoring of space station charging, the technology of plasma in-situ imaging detection is studied. The plasma in-situ imaging detector is one of the first outside scientific payloads of the Chinese space station to detect the space environment. It is installed on the extravehicular platform of the Wentian module, and will carry out multi-element comprehensive detection of ionospheric plasma, including in-situ, imaging, and charging potential. The refined detection data of the low latitude ionosphere will provide plasma parameters for improving the orbital ionospheric model of the space station. And the long-term charging potential data are collected to support the studying of the charging effect of plasma on the space station and promoting the establishment of the space station charging evaluation system.&lt;/sec&gt;&lt;sec&gt;The plasma in-situ imaging detector integrates Langmuir probe, retarding potential analyzer, ion drift meter, reference potentiometer, ion imaging technology, etc. Electron density and electron temperature are measured by Langmuir probe. Ion composition,ion density,ion temperature, and ion drift velocity are measured by retarding potential analyzer and ion drift meter. The ion imaging parameters are obtained by ion imager. The reference potential sensor is available to provide the measurements of charging potential of Wentian module. The Langmuir probe sensor inherits the design of the Langmuir probe sensor of CSES (Zhangheng-1 satellite). The retarding potential analyzer and ion drift meter also inherit the design of CSES (Zhangheng-1 satellite), and improve the design of grid voltage and collector voltage which can be adjusted adaptively according to on orbit state. The ion imager consists of an electrostatic deflection module, a Whalen analyzer and an imaging module. The ion imaging technology is for the first time applied to the field of space environment detection in China.&lt;/sec&gt;&lt;sec&gt;The plasma in-situ imaging detector is tested and calibrated to verify the performance at the National Space Science Center of the Chinese Academy of Sciences. when this paper is submitted, the detector mounted on Wentian module has been successfully launched. Next, the detector will be assembled by astronauts inside the capsule using external interfaces . Then, the detector will be grabbed by the robotic arm and installed on the extravehicular experimental platform to start a long-term exploration mission.&lt;/sec&gt;

Underwater Forward-Looking Sonar Images Target Detection via Speckle Reduction and Scene Prior

Forward-looking sonar (FLS) imagery system plays a significant role in oceanic object recognition and detection since it can overcome the limitation of lighting conditions and reflect the real situation of the underwater environment. However, object detection algorithms for FLS images remain challenging for two main reasons: 1) The noise caused by the coherent characteristic of the scattering phenomenon impairs the detector capture of target information; 2) The scene prior based on the uneven target scale distribution is generally neglected, which leads to the detector generating redundant anchors and slows down detection efficiency. Confronting such challenges, this paper characterizes the noise and the uneven target scale distribution in FLS images as multiplicative speckle noise and scene prior, respectively. Therefore, we propose a novel underwater FLS image detection network, namely UFIDNet, to further improve detection performance by considering speckle noise reduction and scene prior in FLS images. More specifically, a speckle reduction auxiliary branch (SRAB) is designed to introduce additional despeckled supervision information to encourage the feature extractor to produce clean features and share them with the detection pipeline during the training phase. In particular, the noise distribution of FLS images is excavated for synthetic dataset construction and Despeckle Network (DSN) design to obtain despeckled supervision images. In addition, a feature selection strategy (FSS) embedded in detection branch is designed to screen out feature levels that do not match the target size, thus significantly reducing the generation of redundant anchors and improving detection speed. Experimental results show that our UFIDNet achieves 70.5% and 47.3% average precision (AP), 81.3% and 54.6% average recall (AR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max=10</sub> ), 27.0 and 26.1 FPS on two real FLS datasets respectively, outperforming many state-of-the-art general detectors and sonar image detectors.

A proton-recoil track imaging system for fast neutrons: the RIPTIDE detector

Fast neutron detection is often based on the neutron-proton elastic scattering reaction: the ionization caused by recoil protons in a hydrogenous material constitutes the basic information for the design and development of a class of neutron detectors. Although experimental techniques have continuously improved, proton-recoil track imaging remains still at the frontier of n-detection systems, due to the high photon sensitivity required. Several state-of-the-art approaches for neutron tracking by using n-p single and double scattering — referred to as Recoil Proton Track Imaging (RPTI) — can be found in the literature. So far, they have showed limits in terms of detection efficiency, complexity, cost, and implementation. In order to address some of these deficiencies, we propose the design of RIPTIDE, a novel recoil-proton track imaging detector in which the light output produced by a fast scintillator is used to perform a complete reconstruction in space and time of the interaction events. The proposed idea is viable thanks to the dramatic advances in low noise and single photon counting achieved in the last decade by new scientific CMOS cameras as well as pixel sensors, like Timepix or MIMOSIS. In this contribution, we report the advances on the RIPTIDE concept: Geant4 Monte Carlo simulations, light collection tests as well as state-of-the-art approach to image readout, processing and fast analysis.

Research on Delay Line Anode Photon Counting Imaging Detector

Research on Delay Line Anode Photon Counting Imaging Detector

Optimal Irradiation Conditions for Radiopacity Tests of Dental Materials Using General-purpose X-ray Imaging Devices

This study verifies the feasibility and optimal conditions for using a general-purpose x-ray imaging device with a relatively large detector and excellent image quality compared to dental x-ray imaging devices according to international standards. The dental material test specimens were produced in the form of disks from four companies with different radiopacity, and aluminum step wedges was manufactured according to ISO 13116. In order to find the optimal irradiation conditions for general X-ray imaging devices, the distance between the target and the tube was fixed at 700 mm, and the exposure time was fixed at 100 ms. And the tube voltage was 50, 60, 70 kV and the tube current was changed to 40, 80, and 160 mA. As a result, it was sufficient to use general-purpose X-ray imaging devices, and the best results were obtained under the optimal conditions of 60 kV and 40 mA.