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- 摘要
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- 实验方案
- 产品
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Accurate modeling of event-by-event backprojection for a germanium semiconductor Compton camera for system response evaluation in the LM-ML-EM image reconstruction method
摘要： We develop an image reconstruction method, considering the physical phenomenon in the measurement process of a Compton camera. The image quality is improved by applying an accurate error model of the Compton scattering angle. The angular error has two properties: an error distribution function specific to the detector material and the variation of its function parameters, depending on each measurement event. We incorporate these factors into the backprojection of the list-mode maximum-likelihood expectation-maximization method as the system response function. We apply our image reconstruction method to simulated data assumed to be measured by a Ge-semiconductor Compton camera GREI, and the imaging data of a tumor-bearing live mouse obtained using GREI. This method is evaluated by comparing an image with variable angular error with that having fixed angular error. The consideration of the variable angle estimation error improves the spatial resolution and reduces image roughness.
关键词： Ge-semiconductor,image reconstruction,Compton camera,LM-ML-EM method,Doppler broadening
更新于2025-09-23 15:19:57
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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
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Annihilation gamma imaging for carbon ion beam range monitoring using Si/CdTe Compton camera
摘要： In this study, we performed on-beam monitoring of 511-keV annihilation gamma emissions using a Compton camera. Beam monitoring experiments were conducted using carbon ion beams of 290 MeV/u irradiated on a polymethyl methacrylate (PMMA) phantom. The intensity of the beams was 3×10^9 particles per pulse, with 20 pulses per minute. A Compton camera based on a silicon/cadmium telluride (Si/CdTe) detector was used to monitor the annihilation gamma rays emitted from the phantom. We successfully reconstructed the energy events of 511-keV annihilation gamma rays and developed Compton images using a simple back-projection method. The distribution of the annihilation gamma ray generation traced the beam trajectory and the peak intensity position was a few millimeters shorter than the Bragg peak position. Moreover, the effect of the beam range shifter with 30-, 60-, and 90-mm water equivalent thickness was clearly visualized in the reconstructed Compton images. The experimentally measured values of the corresponding range shifts in the PMMA phantom (28.70 mm, 52.49 mm, and 76.77 mm, respectively) were consistent with the shifts of the Bragg peak position (25.50 mm, 51.30 mm and 76.70 mm, respectively) evaluated by Monte Carlo simulation. The results show that the Si/CdTe Compton camera has strong potential for on-beam monitoring of annihilation gamma rays in particle therapy in clinical situations.
关键词： Compton camera,Beam monitoring,Annihilation gamma imaging,Carbon ion radiotherapy
更新于2025-09-19 17:15:36
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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
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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