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Novel method to measure the intrinsic spatial resolution in PET detectors based on monolithic crystals
摘要： The main aim of this work is to provide a method to retrieve the intrinsic spatial resolution of a gamma-ray detector block based on monolithic crystals within an assembled scanner. This method consists on a discrimination of the data using a software collimation process. The results are compared with an alternative method of separating two detector blocks far enough to produce a "virtual" source collimation due to the geometric constraints on the allowed coincidence event angles. A theoretical model has been deduced to fit the measured light distribution profiles, allowing estimating the detector intrinsic spatial resolution. The detector intrinsic spatial resolution is expected to follow a Gaussian distribution and the positron-emitter source shape, given the small size of a 22Na source with 0.25 mm in diameter, can be assumed to follow a Lorentzian profile. However, the collimation of the data modifies the source shape that is no longer a pure Lorentzian distribution. Therefore, the model is based on the convolution of a Gaussian shaped distribution (contribution of the detector) and a modified Lorentzian distribution (contribution of the collimated source profile) that takes into account the collimation effect. Three LYSO crystals geometries have been studied in the present work, namely a 10 mm thick trapezoidal monolithic block, and two rectangular monolithic blocks with thicknesses of 15 mm and 20 mm, respectively. All the blocks have size dimensions of 50 mm × 50 mm. The experimental results yielded an intrinsic detector spatial resolution of 0.64 ± 0.02 mm, 0.82 ± 0.02 and 1.07 ± 0.03 mm, for the 10 mm, 15 mm and 20 mm thick blocks, respectively, when the source was placed at the center of the detector. The detector intrinsic spatial resolution was moreover evaluated across one of the axis of each crystal. These values worsen to an average value of 0.68 ± 0.04 mm, 0.90 ± 0.14 and 1.29 ± 0.19 mm, respectively, when the whole crystal size is considered, as expected. These tests show an accurate method to determine the intrinsic spatial resolution of monolithic-based detector blocks, once assembled in the PET system.
关键词： Intrinsic spatial resolution,SiPM array,Monolithic blocks,Positron Emission Tomography,Gamma ray detectors
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 7th International Conference on Photonics (ICP) - Kuah (2018.4.9-2018.4.11)] 2018 IEEE 7th International Conference on Photonics (ICP) - Differential Cross Spectrum Technique for Improving the Spatial Resolution of BOTDR Sensor
摘要： We propose a technique in BOTDR fiber sensor to generate a pair of pulsed probes via intensity modulation scheme for measuring distributed strain at high spatial resolution. The first probe consists of a long- and short duration of pulses separated by a short interval. The second probe only has the long pulse of the first probe. Introducing FFT in correlating the backscattered signals sampled by wide and narrow window functions for each probe gives narrow Brillouin spectrum width. The subtraction of the correlated signals obtained by the two probes results in high spatial resolution measurement. The intensity modulation makes it easier to generate the pair of pulsed probes having the same waveform of the long pulse and to obtain the results according to the measurement principle. We have achieved 0.2 m spatial resolution and 3.2 MHz Brillouin frequency accuracy in measuring a 350 m fiber.
关键词： BOTDR,spatial resolution,distributed fiber sensor,Brillouin frequency shift
更新于2025-09-23 15:23:52
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Multimodal hard x-ray imaging with resolution approaching 10 nm for studies in material science
摘要： We report multimodal scanning hard x-ray imaging with spatial resolution approaching 10 nm and its application to contemporary studies in the field of material science. The high spatial resolution is achieved by focusing hard x-rays with two crossed multilayer Laue lenses and raster-scanning a sample with respect to the nanofocusing optics. Various techniques are used to characterize and verify the achieved focus size and imaging resolution. The multimodal imaging is realized by utilizing simultaneously absorption-, phase-, and fluorescence-contrast mechanisms. The combination of high spatial resolution and multimodal imaging enables a comprehensive study of a sample on a very fine length scale. In this work, the unique multimodal imaging capability was used to investigate a mixed ionic-electronic conducting ceramic-based membrane material employed in solid oxide fuel cells and membrane separations (compound of Ce0.8Gd0.2O2?x and CoFe2O4) which revealed the existence of an emergent material phase and quantified the chemical complexity at the nanoscale.
关键词： mixed ionic-electronic conducting membrane,x-ray nanoscale imaging,multimodal imaging,high spatial resolution
更新于2025-09-23 15:23:52
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Applications of nanostructures in wide-field, label-free super resolution microscopy
摘要： Super resolution imaging capable of resolving details beyond the diffraction limit is highly desired in many scientific and application fields, including bio-medicine, nanomaterial science, and opto-electronic integration. Up to now, many different methods have been proposed, among which wide-field, label-free super resolution microscopy is indispensable due to its good applicability to diverse sample types, large field of view (FOV), and high imaging speed. In recent years, nanostructures have made a crucial contribution to the wide-field, label-free subdiffraction microscopy, with various working mechanisms and configuration designs. This review summarizes the recent applications of the nanostructures in the wide-field, label-free super resolution microscopy, with the emphasis on the designs of hyperlens with hyperbolic dispersion, microsphere with “nano-jets”, and nanowire ring illumination microscopy based on spatial frequency shift effect. The bottlenecks of the current techniques and possible solutions are also discussed.
关键词： spatial resolution,nanowire,metamaterials,optical microscopy
更新于2025-09-23 15:23:52
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Bistatic SAR: Forecasting Spatial Resolution
摘要： This paper derives closed form expressions for bistatic synthetic aperture radar spatial resolution of a generalized system from the k-space or the wavenumber domain. These spatial resolution equations have not previously appeared in the literature. From these equations, significant resolution is found in both range and cross-range forecasting a forward-scatter bistatic synthetic aperture radar image when the elevation angles of each bistatic platform are significantly different. Simulation and lab tests demonstrated the forward scatter resolution.
关键词： image resolution,synthetic aperture radar,radar remote sensing,spatial resolution,radar imaging,bistatic radar,microwave imaging
更新于2025-09-23 15:22:29
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Spectral Zooming and Resolution Limits of Spatial Spectral Compressive Spectral Imagers
摘要： The recently introduced Spatial Spectral Compressive Spectral Imager (SSCSI) has been proposed as an alternative to carry out spatial and spectral coding using a binary on-off coded aperture. In SSCSI, the pixel pitch size of the coded aperture, as well as its location with respect to the detector array, play a critical role in the quality of image reconstruction. In this paper, a rigorous discretization model for this architecture is developed, based on a light propagation analysis across the imager. The attainable spatial and spectral resolution, and the various parameters affecting them, is derived through this process. Much like the displacement of zoom lens components leads to higher spatial resolution of a scene, a shift of the coded aperture in the SSCSI in reference to the detector leads to higher spectral resolution. This allows the recovery of spectrally detailed datacubes by physically displacing the mask towards the spectral plane. To prove the underlying concepts, computer simulations and experimental data are presented in this paper.
关键词： discretization model,spatial resolution,coded aperture,Spectral imaging,compressive sensing,spectral resolution
更新于2025-09-23 15:22:29
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Testing of the optical chain mockup of H-alpha and Visible Spectroscopy for ITER
摘要： H-alpha and Visible Spectroscopy is one of the ITER first-plasma diagnostics providing full poloidal coverage of plasma scrape-off layer near the first wall. There are two poloidal-view channels in Equatorial Port Plug 11 (EPP11), one tangential-view channel in Equatorial Port Plug 12 (EPP12), and one divertor-view channel in Upper Port Plug 02 (UPP02). At the moment, the final design phase is ongoing, requiring proper testing of design solutions to identify the realistic optical parameters and the problems related to the manufacturing, alignment, calibration and stability issues. A full-scale mockup of the whole optical chain has been built for this purpose. It comprises the most important units starting from the in-vessel optical front-end (First Mirror Unit) to the Interspace relay optics (Long-Focus Spectral Telescope), and to the Optical Bench Assembly located in the Port Cell, where the collected light is coupled to the imaging cameras and to the complex optical fiber bundle transmitting it to the various detectors and spectrometers to be located in the ITER Diagnostic Building. The detailed optical design, analyses, benchmarking and test results are reported with a main focus on the alignment/calibration issues, and on the spatial resolution measured. The measurements have been performed in the wide spectral range 450–700 nm, which is required for the monitoring of the H-alpha, Beryllium and other impurity emission line profiles with probable local peaks considered as the most important ITER safety-relevant task for the passive visible spectroscopy diagnostics.
关键词： ITER,Spatial resolution,Spectroscopy
更新于2025-09-23 15:22:29
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Individual mangrove tree measurement using UAV-based LiDAR data: Possibilities and challenges
摘要： Individual mangrove tree parameters are necessary for the efficient management and protection of this unique ecosystem, but to measure them using remote sensing (RS) is still a new and challenging task due to the high clumping density of mangrove crowns and the relatively low spatial resolution of RS data. Unmanned aerial vehicles (UAVs), as an emerging RS technique, significantly improves the spatial resolution, but has not been used for individual mangrove analysis. This study presents the first investigation into the possibility of individual tree detection and delineation (ITDD) for mangroves using light detection and ranging (LiDAR) data (91 pt./m2) collected from UAV. Specifically, we aim to detect and measure tree height (TH) and crown diameter (CD) of each mangrove tree, and analyze the impact of crown clumping density and spatial resolution on mangrove ITDD. To this end, we combined the variable window filtering method and marker controlled watershed segmentation algorithm, and successfully delineated 46.0% of the 126 field measured mangroves. This was promising considering the complexity of mangrove forest. TH and CD were estimated with higher accuracies than previous studies. The isolated trees, with the lowest clumping density, were delineated with the highest accuracy. To identify the optimal spatial resolution of canopy height model (CHM), we defined four spatial resolutions (0.1 m, 0.25 m, 0.5 m, and 1 m) and conducted a simulation. Based on the results, we propose a rule-of-thumb that the spatial resolution should be finer than one-fourth of CD for ITDD, which is also applicable to other forest types. The main difficulty for mangrove ITDD is an overall under-detection of trees, which is caused by the high clumping density and limited height difference between adjacent mangroves. We recommend combining UAV LiDAR with imagery and terrestrial LiDAR to improve the mangrove ITDD performance.
关键词： LiDAR,Unmanned aerial vehicle,Mangrove,Individual crown,Optimal spatial resolution
更新于2025-09-23 15:22:29
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[Advances in Intelligent Systems and Computing] Soft Computing for Problem Solving Volume 817 (SocProS 2017, Volume 2) || Temperature Resolution and Spatial Resolution Improvement of BOCDR-Based DTS System Using Particle Swarm Optimization Algorithm
摘要： Temperature resolution and spatial resolution are major performance metrics in any distributed temperature sensing (DTS) system. In this paper, we have presented a detailed analysis on the performance of a Brillouin optical correlation domain reflectometry (BOCDR)-based DTS (BOCDR-DTS) system. Particle swarm optimization (PSO) evolutionary algorithm is being used in this paper to improve the performance of the proposed BOCDR-DTS system. Using this optimization algorithm, we minimized the Brillouin frequency shift (BFS) error in sensing system. As a consequence of this, the achieved temperature and spatial resolution are ~0.839 °C and ~43 cm, respectively. The results were simulated using MATLAB version 15.0.
关键词： Spontaneous Brillouin scattering,Distributed temperature sensing,Particle swarm optimization (PSO),Temperature resolution and spatial resolution,Brillouin frequency shift,Optical correlation domain reflectometry (OCDR)
更新于2025-09-23 15:21:21
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Use of YAP(Ce) in the development of high spatial resolution radiation imaging detectors
摘要： A scintillator with a high light output is considered to be required for the development of high spatial resolution radiation imaging detectors. In contrast to this scientific consensus, we found that high spatial resolution images can be obtained using a medium light output scintillator comprising cerium-doped yttrium aluminum perovskite, YA1O3 (YAP(Ce)). We evaluated the performance of a radiation imaging detector comprising a 0.5 mm thick YAP(Ce) plate, which was optically coupled to a 25.4 mm (1-inch) square position-sensitive photomultiplier. The Anger principle was used to calculate the radiation positions. The spatial resolution and energy resolution for the imaging detector with 5.5 MeV alpha particles were 0.2 mm full width at half-maximum (FWHM) and 7.4% FWHM, respectively. The spatial resolutions for 60 keV gamma photons and ~32 keV X-rays were ~ 0.6 mm FWHM and ~ 0.8 mm FWHM, respectively. The spatial resolution of the detector when imaging beta particles at a maximum energy of 254 keV was less than 0.6 mm FWHM. We conclude that YAP(Ce) is a promising scintillator for developing high spatial resolution and high energy resolution radiation detectors for imaging alpha particles, beta particles, and gamma photons.
关键词： YAP(Ce),energy resolution,position-sensitive photomultiplier,spatial resolution
更新于2025-09-23 15:21:21