- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Spectroscopic Compton imaging of prompt gamma emission at the MeV energy range
摘要： This work explores a novel tomographic approach to PGAA that is both quantitative and spatially resolved, adapted from a clinical "proton beam range finder" in which MeV gamma rays are imaged by coincidence measurements of Compton scattered gamma rays with multi-detector arrays. We performed preliminary measurements using a Compton camera made with CdZnTe detector arrays on a series of test samples with high-energy (> 1 MeV) gamma emission lines. 3D image reconstructions were performed on the 2.2 MeV peak from H. The image reconstruction methods were also evaluated using the emission data generated by Monte Carlo simulations under ideal conditions.
关键词： 3D elemental distribution,Compton imaging,Prompt gamma activation analysis
更新于2025-09-23 15:23:52
-
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
-
Measurement of the Modulation Transfer Function for a Backscatter Radiography System Used in Nondestructive Examination
摘要： The need for subsurface flaw detection in materials has led to the recent development of a backscatter radiography system. In order to achieve the optimal system design, the modulation transfer function (MTF) must be characterized for the backscatter system. Although several established methods exist for medical imaging systems, these techniques cannot be directly applied to the backscatter system. The goal of this study was to alter the transmission MTF measurement methods using the bar pattern and edge technique so that accurate and reliable results can be obtained for the backscatter system. Test tools were developed in order to carry out these measurements, with the ultimate goal of providing a target for quality assurance testing of the equipment. Although the edge method results were higher than the bar pattern method, the difference in magnitude was less than 0.1. The MTF measurements indicated the importance of target design and positioning in order to achieve accurate results for a backscatter radiography system used in nondescructive examination.
关键词： X-Ray Imaging,Radiography,Compton Imaging
更新于2025-09-23 15:21:01
-
Prototype of an array SiPM-based scintillator Compton camera for radioactive materials detection
摘要： Purpose The Compton camera, which visualizes the distribution of gamma-ray sources based on the kinematics of Compton scattering, has advantage of wide field of view, broad range of energy and compact structure. Methods In this study, we proposed a prototype of Compton camera, which included array silicon photomultiplier (SiPM)-based position-sensitive detectors, data acquisition (DAQ) system and image reconstruction system. The detectors were composed of Ce-doped Gd3Al2Ga3O12 scintillator arrays and pixel Si-PM arrays. In DAQ system, symmetric charge division circuit, impedance bridge circuit and the delay coincidence algorithm were designed to record coincidence events. Simple back-projection algorithm and list-mode maximum likelihood expectation maximization algorithm were adopted for image reconstruction. The coordinate of longitude and latitude was used for image fusion. Results The performance of this Compton camera prototype system was evaluated. The results indicated that this system was able to locate a 137Cs point source within 20 s with the corresponding radiation dose of ~ 1.0 μSv/h. The angular resolution of point source was ~ 7° (FWHM), and the total energy resolution of 662 keV was 7.2%. Furthermore, we succeeded in separating two point sources of different energy [22Na (511 keV), 137Cs (662 keV)] in laboratory test. Conclusions This prototype of scintillator Compton camera offers capabilities for applications like source term investigation and radioactive materials detection.
关键词： Scintillator Compton camera,Image reconstruction,Compton imaging,Silicon photomultipliers
更新于2025-09-19 17:15:36
-
Development of a 3-D scintillator detector for Compton imaging based on laser engraving
摘要： Y2SiO5: Ce (YSO) scintillation with characteristics of high light yield, fast decay time and high Compton scattering fraction shows good application potential for Compton imaging. In this study, we propose a three-dimensional (3-D) scintillator detector, which is segmented by the YSO monolithic rods and pixelated by sub-surface laser engraving (SSLE) in the depth direction. Two arrays of silicon photomultipliers are optically coupled to the YSO array at each end, in which the pixels are designed for a one-to-one match. By identifying the location number of array pixels and measuring depth-of-interaction (DOI) of pixelated scintillator rods, the interaction coordinates of gamma photon can be obtained accurately. After energy consistent calibration, the energy resolutions of the pixels in 3-D detector were evaluated. The imaging test results indicate that the detector has a capability to locate a 0.1 μSv/h Cs-137 gamma-ray source within 90 seconds in 4π field-of-view (FOV). The efficiency of the imaging events is 2.2 %. By using the maximum likelihood expectation maximization (MLEM) algorithm with 10 iterations, the full width at half maximum (FWHM) of the reconstructed hotspot decreases to less than 9.0 °. This configuration mainly simplifies the calculation of interaction coordinates compared to the center of gravity method. Moreover, the higher segment precision for DOI estimation are realized thanks to the SSLE technique. The 3-D scintillator detector achieves 4π Compton imaging with high detection efficiency and high localization accuracy.
关键词： Sub-surface laser engraving,Scintillation detectors,Compton imaging,Image reconstruction
更新于2025-09-12 10:27:22
-
Compton camera based on Timepix3 technology
摘要： The Compton camera concept is based on the reconstruction of recorded Compton scattering events of incoming gamma rays. The scattering of primary gamma ray occurs in the first detector (called scattering detector — usually thin) recording the position and energy of the recoiled electron. The scattered gamma quantum continues towards the second detector (called absorption detector - usually thick) where it is absorbed. The second detector records the energy and the position of this scattered gamma. Using the Compton scattering equation it is possible to determine the scattering angle, and estimate possible directions of the original gamma ray as a surface of a cone. When the Compton camera records the number of such events, the location and the shape of the gamma source can be reconstructed. Timepix3, a hybrid single photon counting imaging pixel detector, is a perfect device for creation of a compact Compton camera. Timepix3 is an event based readout chip (every hit pixel is immediately sent to a readout) and can record the time-of-arrival (ToA) and energy of an incident gamma simultaneously in each pixel. The chip offers high energy resolution (1 keV at 60 keV, 7 keV at 356 keV), as well as time resolution (1.6 ns). The Timepix3 readout chip can be combined with different sensor materials (Si, CdTe, CZT). In this contribution, we present a very compact detector system for imaging with gamma-rays using the Compton camera principle. The system consists of at least two layers of hybrid pixel detectors Timepix3 with the sensors being optimized for gamma-ray tracking. The front detector layer (scattering) is made of silicon of 1 mm thickness, while the last layer (absorbing) is equipped with thick CdTe or CZT sensors up to 2 mm in thickness. The total absorption of the whole detector can be very high if several CdTe or CZT layers are used. The maximal number of layers is not limited, but the practical evaluation was performed with 2 layers. Thanks to Timepix3 simultaneous measurement of ToA and energy, it is possible to precisely detect coincidence events in the detector layers. Based on the energy and position of these events, it is possible to estimate the possible direction of the original gamma. The angular resolution of the presented Compton camera depends on the detected energy, and it is in the order of 1 degree.
关键词： PET PET/CT,coronary CT angiography (CTA),Gamma camera,Particle tracking detectors,Compton imaging,SPECT
更新于2025-09-09 09:28:46
-
Double photon emission coincidence imaging with GAGG-SiPM Compton camera
摘要： Compton imaging is a promising gamma-ray imaging method based on the Compton scattering kinematics due to high Compton scattering probability for sub-MeV to MeV gamma-rays. A conventional Compton camera has a disadvantage of low signal-to-background ratio (SBR), which is caused by drawing of multiple Compton cones. A method to solve this fundamental problem is the double-photon emission computed tomography (DPECT), which uses the coincidence detection for cascade gamma-rays and significantly increases the SBR using intersections of two Compton cones. In this study, we demonstrated the DPECT method by using 134Cs radioisotope, which is one of important radioisotopes for the imaging of fuel debris, with two Ce:Gd3(Al,Ga)5O12 (GAGG) scintillator Compton cameras.
关键词： Compton camera,Double photon emission coincidence imaging,Compton imaging,Caesium-134
更新于2025-09-04 15:30:14