分类： 物理学 >> 核物理学 提交时间： 2023-07-24
摘要： The in-core self-powered neutron detector (SPND) acts as a key measuring device for the monitoring of parametersand evaluation of the operating conditionsof nuclear reactors. Prompt detection and tolerance of faulty SPNDsare indispensable forreliable reactor management. To completely extract the correlated state information of SPNDs, we constructeda twin model based on ageneralized regression neural network (GRNN)that represents the common relationshipsamong overall signals. Faulty SPNDswere determined because of the functional concordance of the twin model and real monitoring systems, which calculated the error probability distribution between the model outputs and real values. Faultdetection follows a tolerance phase to reinforce the stability of the twin model in the case of massive failures. Aweighted K-nearest neighbor model was employed to reasonably reconstruct the valuesof the faulty signals and guarantee data purity. The experimental evaluation of the proposed method showedpromising results,with excellentoutput consistency and high detection accuracy for bothsingle- andmultiple-point faulty SPNDs. Forunexpected excessive failures, the proposed tolerance approach can efficiently repair fault behaviors and enhance the prediction performance of the twin model.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： To achieve a maximum compression of system matrix in positron emission tomography (PET) image reconstruction, we proposed a polygonal image pixel division strategy in accordance with rotationally symmetric PET geometry. Geometrical definition and indexing rule for polygonal pixels were established. Image conversion from polygonal pixel structure to conventional rectangular pixel structure was implemented using a conversion matrix. A set of test images were analytically defined in polygonal pixel structure, converted to conventional rectangular pixel based images, and correctly displayed which verified the correctness of the image definition, conversion description and conversion of polygonal pixel structure. A compressed system matrix for PET image recon was generated by tap model and tested by forward-projecting three different distributions of radioactive sources to the sinogram domain and comparing them with theoretical predictions. On a practical small animal PET scanner, a compress ratio of 12.6:1 of the system matrix size was achieved with the polygonal pixel structure, comparing with the conventional rectangular pixel based tap-mode one. OS-EM iterative image reconstruction algorithms with the polygonal and conventional Cartesian pixel grid were developed. A hot rod phantom was detected and reconstructed based on these two grids with reasonable time cost. Image resolution of reconstructed images was both 1.35 mm. We conclude that it is feasible to reconstruct and display images in a polygonal image pixel structure based on a compressed system matrix in PET image reconstruction.
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