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- 2017
- spectral reconstruction
- interference
- polarization
- transform
- imaging spectrometer
- Optoelectronic Information Science and Engineering
- BITTT
- Zhejiang University
- Guilin University of Aerospace Technology
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Development of simultaneous PET and Compton imaging using GAGG-SiPM based pixel detectors
摘要： Positron emission tomography (PET) is considered an important and powerful tool for molecular imaging and medical diagnosis with its high sensitivity. Further, single-photon emission CT (SPECT) is another important imaging modality providing different types of information in medical diagnosis. On the other hand, Compton imaging is a promising technique for future molecular imaging with multi-nuclides based on Compton scattering kinetics. In this regard, previously, we have developed gadolinium aluminum gallium garnet (GAGG)-scintillation-based PET systems and GAGG-scintillation-based Compton imaging systems for environmental applications. Here, we propose and develop a novel PET–Compton hybrid simultaneous imager based on a two-layer structure using thin scatterers and thick absorbers for multi-nuclide imaging, for e.g., simultaneous imaging of PET and SPECT tracers such as 18F-FDG and 111In, respectively. For achieving good spatial resolution of the Compton imager, the energy resolution of the utilized scintillators forms one of the most important characteristics. In this regard, GAGG is a promising scintillator because of its high light yield of over 50 000 photon/MeV and excellent energy resolution of 4% with no background radiation and moderate decay time. In this study, we present the development of a simultaneous PET–Compton detector that consists of an 8 × 8 multi-pixel photon counter/SiPM (MPPC) array individually coupled with a 2.5 × 2.5 × 9-mm3 Ce:Gd3Ga2.7Al2.3O12 scintillators (absorbers) for proof of concept of simultaneous PET and SPECT imaging. The pixel size of the MPPC is 3 mm × 3 mm, and it is operated at 55 V at room temperature. The signals from the MPPC scintillators are individually amplified and converted with a dynamic time over threshold (dTOT) circuit to record the energy and timing information. In image reconstruction, the data acquired with the use of the developed modules are classified into events of either Compton imaging or PET imaging by coincidence detection between scatterer and absorber or between absorber and absorber, respectively. The coincidence events between absorber and absorber are regarded as PET annihilation-gamma events and those between scatterer and absorber are used as Compton imaging events. In our experiment, images of 111In and 18F-FDG, which are used as multi-nuclide tracers, are acquired simultaneously using the developed detector for Compton imaging and PET imaging. We believe that our approach is a significant step forward for medical imaging and related fields.
关键词： Scintillator,Single-photon emission CT,SiPM,Positron emission tomography,Compton imaging
更新于2025-09-23 15:23:52
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Development of a sub-miniature gamma camera for multimodal imaging system
摘要： In the recent past, gamma-ray imaging detectors have achieved an intrinsic spatial resolution of less than 1 mm within a few centimeters of a useful field of view (UFOV). Unlike to conventional gamma cameras, which are large and heavy, the compact gamma-ray imaging detectors can improve the performances of the gamma cameras used in the various fields. In this study, we developed a sub-miniature gamma camera for a multimodal imaging system. The camera has a gamma-ray detector, miniature electronics modules, and a diverging hole collimator. The detector consisted of the sub-millimeter pixelated Ce:GAGG array and the silicon photomultiplier (SiPM) array module. We organized the miniature electronics modules according to the functions; an MPPC base board, analog signal processing board, integrated power supply board, and compact data acquisition (DAQ) base board. The diverging hole collimator widened an imaging area of the gamma camera from the UFOV of the detector. On the detector side, dimensions of each hole and septa were identical to the pixel and inter-pixel thickness of the reflector of scintillator array. For the intrinsic performance test, we acquired a flood map image of 729 (27 × 27) scintillator pixels, and the energy resolution was 18.9 % for an integrated energy histogram of 99mTc (140 keV). For the extrinsic performance test, we used the 57Co sheet source, and made a 99mTc line source using a capillary tube. The sources located at 10 cm apart from the collimator surface. The imaging area was three times wider than the UFOV of the detector. The system sensitivity was 19 CPM/μCi and the spatial resolution was 3.5 mm. The usability of the proposed gamma camera will not be confined to existing applications due to its compactness and novelty.
关键词： Sub-miniature gamma camera,Gamma camera performance evaluation,Front-end electronics,Multimodal imaging system,Diverging hole collimator
更新于2025-09-23 15:23:52
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Status of the GlueX DIRC
摘要： This year we start assembling the DIRC detector to upgrade the particle identification capabilities in the forward region of the GlueX detector in Hall D at Jefferson Lab. The main components of the GlueX DIRC are the four bar boxes (reused from the decommissioned BaBar DIRC) and two photon cameras, which were designed based on the prototype for the SuperB FDIRC. The delicate bar boxes have already arrived at JLab from SLAC, where they have been stored for the last ten years. They will be attached to the newly built photon cameras and installed in Hall D already for the 2019 spring run. We present the status of the GlueX DIRC project including the ongoing R&D and the plan for the future.
关键词： Particle identification,Cherenkov counter,Ring imaging,DIRC
更新于2025-09-23 15:23:52
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Neural network-based hybrid signal processing approach for resolving thin marine protective coating by terahertz pulsed imaging
摘要： A novel approach was presented to enhance the capability of resolving thin coating layers using terahertz pulsed imaging (TPI) based on a neural network-based hybrid signal procession method, which is of great significance for in-line painting applications. In the present work, Terahertz detected signals were obtained by numerical simulation using finite difference time domain (FDTD) method. Models of marine protective coatings with different coating structures were calculated and analyzed. Different signal pre-processing techniques, including Fourier deconvolution, Fast Fourier Transform and wavelet analysis, were employed on the terahertz signals respectively to obtain various signal features. The processed signal was subsequently adopted as the input vectors for a neural network (NN). The optimization procedure for determining the architecture of neural network was investigated and the evaluated results obtained by the different networks were compared. Furthermore, the predicted results of thinner coating layer obtained by multiple-regression analysis method and BP network prediction method respectively were compared. The analysis demonstrated that the best prediction performance was achieved by neural network technique combined with wavelet analysis. Therefore, the hybrid signal processing approach could be recommended for terahertz non-destructive testing applications of marine protective coating.
关键词： Terahertz pulsed imaging,Non-destructive testing,Neural network,Thin marine protective coating
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Singapore, Singapore (2018.4.22-2018.4.26)] 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Cell Detection in Microfluidic System by Terahertz Technique
摘要： In this research, a microfluidic system combined with terahertz technique is designed and used for cell detection. Terahertz wave signal, generated by photoconductive antenna, penetrates through cells, medium, and the materials of the microfluidic device. The reflective terahertz signal can be collected by detector and transformed into frequency domain signals. By comparing these signals, this would help us to find out the characteristic signal of material at certain frequency on the order of terahertz range. Furthermore, cells and medium are injected into the microfluidic device. The experiment results demonstrate the capability to differentiate various kinds of material. In the future, this approach can help us to distinguish the cancer cells among normal cells.
关键词： terahertz,microfluidic,Polyscanner-FL7,cell imaging
更新于2025-09-23 15:23:52
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Pattern Reconfigurable Wideband Loop Antenna for Thorax Imaging
摘要： A unidirectional loop antenna that can achieve wideband pattern re-configurability from -40 to +40 degrees in azimuth plane is presented. The antenna is designed to fulfill the multi-slice (level) scanning requirements of electromagnetic imaging (EMI) systems for thorax imaging. To overcome the need for positioning of several antenna-arrays, and hence eliminate the mutual coupling related complications, a square-loop antenna with reconfigurable pattern is designed. To create a unidirectional radiation, the loop is loaded with capacitive gaps, which convert its radiation mechanism to that of two virtual dipole arrays with quadrature phase excitation. By utilizing this feature, the location of the gaps are varied on the loop's structure to form virtual dipole arrays in different directions, thus rotating the radiation pattern without physically moving the structure of the antenna. As a proof of concept, six gaps were created on the loop and each gap is loaded with a PIN diode to electronically switch between the positions of the designed gaps, thus enabling changing the radiation direction. The proposed antenna can achieve a compact size of 0.32λ×0.32λ×0.002λ (λ is the wavelength of the lowest resonance of the antenna) and a wide fractional bandwidth of 32% at 0.8-1.15 GHz, with a peak gain and front-to-back-ratio of 2.1 dBi and 8 dB, respectively. The antenna is successfully tested on a thorax imaging platform to detect small volume of water (5 mL) inside lungs as an emulation of early pulmonary edema.
关键词： unidirectional antenna,virtual dipole array,pattern reconfigurable antenna,loop antenna,Electromagnetic imaging,wideband antenna
更新于2025-09-23 15:23:52
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Magneto-optical imaging characteristics of weld defects under alternating and rotating magnetic field excitation
摘要： This paper mainly examines the characteristics of magneto-optical (MO) images of weld defects under alternating and rotating magnetic field excitation. Weld defects including surface and subsurface defects were subjected to magneto-optical imaging (MOI) nondestructive testing (NDT) experiments. The MO images of different weld defects under alternating magnetic field excitation and rotating magnetic field excitation have been compared to determine the best effect of nondestructive testing, and a cruciform welding seam was used to verify the detection effect of rotating magnetic field. Besides, the values of standard deviation and maximum difference have been determined to analyze the difference in the effects of two magnetic fields, and image processing methods were applied to extract defect information, such as histogram equalization. Experimental results show that the optimal excitation voltage and lift-off value of rotating magnetic field are 120 V and 20 mm, respectively; image histogram equalization can significantly improve the contrast of MO images, and there is a distinct difference in the detection effect of two magnetic fields. Under the same excitation conditions, the detection effect of rotating magnetic fields is always better than the effect of alternating magnetic fields, and rotating magnetic field excitation has obvious advantages in detecting multidirection and subsurface defects in that the detection depth can reach about 8 mm.
关键词： Magneto-optical imaging,Electromagnetic optics,Nondestructive testing,Rotating magnetic field
更新于2025-09-23 15:23:52
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Face Detection and Verification Using Lensless Cameras
摘要： Camera-based face detection and verification have advanced to the point where they are ready to be integrated into myriad applications, from household appliances to Internet of Things (IoT) devices to drones. Many of these applications impose stringent constraints on the form-factor, weight, and cost of the camera package that cannot be met by current-generation lens-based imagers. Lensless imaging systems provide an increasingly promising alternative that radically changes the form-factor and reduces the weight and cost of a camera system. However, lensless imagers currently cannot offer the same image resolution and clarity of their lens-based counterparts. This paper details a first-of-its-kind evaluation of the potential and efficacy of lensless imaging systems for face detection and verification. We propose the usage of existing deep learning techniques for face detection and verification that account for the resolution, noise, and artifacts inherent in today's lensless cameras. We demonstrate that both face detection and verification can be performed with high accuracy from the images acquired from lensless cameras, which paves the way to their integration into new applications. A key component of our study is a dataset of 24,112 lensless camera images captured using FlatCam of 88 subjects in a range of different operating conditions.
关键词： coded aperture,face verification,lensless imaging,deep learning,machine vision,face detection
更新于2025-09-23 15:23:52
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Learning compact q-space representations for multi-shell diffusion-weighted MRI
摘要： Diffusion-weighted MRI measures the direction and scale of the local diffusion process in every voxel through its spectrum in q-space, typically acquired in one or more shells. Recent developments in microstructure imaging and multi-tissue decomposition have sparked renewed attention in the radial b-value dependence of the signal. Applications in motion correction and outlier rejection therefore require a compact linear signal representation that extends over the radial as well as angular domain. Here, we introduce SHARD, a data-driven representation of the q-space signal based on spherical harmonics and a radial decomposition into orthonormal components. This representation provides a complete, orthogonal signal basis, tailored to the spherical geometry of q-space and calibrated to the data at hand. We demonstrate that the rank-reduced decomposition outperforms model-based alternatives in human brain data, whilst faithfully capturing the micro- and meso-structural information in the signal. Furthermore, we validate the potential of joint radial-spherical as compared to single-shell representations. As such, SHARD is optimally suited for applications that require low-rank signal predictions, such as motion correction and outlier rejection. Finally, we illustrate its application for the latter using outlier robust regression.
关键词： Diffusion-weighted imaging,Blind source separation,Multi-shell HARDI,Dimensionality reduction
更新于2025-09-23 15:23:52
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A conjugated-polymer-based ratiometric nanoprobe for evaluating in-vivo hepatotoxicity induced by herbal medicine via MSOT imaging
摘要： Herbal medicines are widely used around the world, while some of them are associated with adverse effects like herb-induced liver injury due to oxidative/nitrosative stress resulted from hepatically-generated ROS/RNS. It is of significance to accurately evaluate herbal-medicine-induced hepatotoxicity, since it would help provide effective monitoring method of the safety of herbal remedies. Herein we designed a ratiometric nanoprobe for in vivo imaging hepatic injury induced by herbal medicine (polygonum multiflorum, PM) via specifically responding to NO generated in liver by PM, and with MSOT imaging the precise location of liver injury can be identified. The liposomal nanoprobe consists of a responsive dye (IX-2NH2) which could specifically respond to NO and the diketopyrrolopyrrole-based conjugated polymer (DPP-TT) as the internal reference. Thus we can realize ratiometric optoacoustic detection of herbal-medicine-induced liver injury with 3D information in mouse model in a noninvasive way.
关键词： MSOT,Hepatotoxicity,Optoacoustic imaging,Herbal medicine
更新于2025-09-23 15:23:52