分类： 物理学 >> 核物理学 提交时间： 2023-07-10
摘要： Objective. Lanthanum bromide (LaBr3) crystal has a high energy resolution and time resolution and has been used in Compton cameras (CCs) over the past few decades. However, LaBr3 crystal arrays are difficult to process because LaBr3 is easy to crack and break; thus, few LaBr3-based CC prototypes have been built. In this study, we designed and fabricated a large-pixel LaBr3 CC prototype and evaluated its performance with regard to position, energy, and angular resolution. Approach. We used two 10 10 LaBr3 crystal arrays with a pixel size of 5 mm 5 mm, silicon photomultipliers (SiPMs), and corresponding decoding circuits to construct our prototype. Additionally, a framework based on a Voronoi diagram and a lookup table was developed for list-mode projection data acquisition. Monte Carlo (MC) simulations based on Geant4 and experiments were conducted to evaluate the performance of our CC prototype. Main results. The lateral position resolution was 5 mm, and the maximum deviation in the depth direction was 2.5 and 5 mm for the scatterer and absorber, respectively. The corresponding measured energy resolutions were 7.65% and 8.44%, respectively, at 511 keV. The experimental results of 137Cs point-like sources were consistent with the MC simulation results with regard to the spatial positions and full widths at half maximum (FWHMs). The angular resolution of the fabricated prototype was approximately 6 when a point-like 137Cs source was centrally placed at a distance of 5 cm from the scatterer. Signification. We proposed and investigated a large-pixel LaBr3 CC for the first time and verified its feasibility for use in accurate spatial positioning of radiative sources with a high angular resolution. The proposed CC can satisfy the requirements of radiative source imaging and positioning in the nuclear industry and medical applications.
分类： 物理学 >> 核物理学 提交时间： 2023-06-01
摘要： Compton camera-based prompt gamma (PG) imaging has been proposed for range verification during protontherapy. However, a deviation between the PG and dose distributions, as well as the difference between thereconstructed PG and exact values, limit the effectiveness of the approach in accurate range monitoring duringclinical applications. The aim of the study was to realize a PG-based dose reconstruction with a Comptoncamera, thereby further improving the prediction accuracy of in-vivo range verification and providing a novelmethod for beam monitoring during proton therapy. In this paper, we present an approach based on a subsetdriven origin ensemble with resolution recovery (SD-OE-RR) and a double evolutionary algorithm (DEA) to reconstruct the dose depth profile (DDP) from the gamma events obtained by a Cadmium-Zinc-Telluride(CZT) Compton camera with limited position and energy resolution. Simulations of proton pencil beams withclinical particle rate irradiating phantoms made of different materials and the CT-based thoracic phantom wereused to evaluate the feasibility of the proposed method. The results show that for the monoenergetic protonpencil beam irradiating homogeneous-material box phantom, the accuracy of the reconstructed DDP was within0.3 mm for range prediction and within 5.2% for dose prediction. In particular, for 1.6-Gy irradiation in thetherapy simulation of thoracic tumors, the range deviation of the reconstructed spread-out Bragg peak waswithin 0.8 mm, and the relative dose deviation in the peak area was less than 7% compared to the exact values.The results demonstrate the potential and feasibility of the proposed method in future Compton-based accuratedose reconstruction and range verification during proton therapy.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： Providing an early warning of galactic supernova explosions from neutrino signals is important in studying supernova dynamics and neutrino physics. A dedicated supernova trigger system has been designed and installed in the data acquisition system at Daya Bay and integrated into the worldwide Supernova Early Warning System (SNEWS). Daya Bay's unique feature of eight identically-designed detectors deployed in three separate experimental halls makes the trigger system naturally robust against cosmogenic backgrounds, enabling a prompt analysis of online triggers and a tight control of the false-alert rate. The trigger system is estimated to be fully sensitive to 1987A-type supernova bursts throughout most of the Milky Way. The significant gain in sensitivity of the eight-detector configuration over a mass-equivalent single detector is also estimated. The experience of this online trigger system is applicable to future projects with spatially distributed detectors.
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