【作者】 王浩；

【导师】 谢庆国；

【作者基本信息】 华中科技大学 ， 生物医学工程， 2021， 硕士

【摘要】 正电子发射断层成像(Positron Emission Tomography,PET)是一种能够无创、动态地获取生物体内组织、器官生化反应和代谢信息的功能成像技术,在临床诊断和新药研发等领域有重要应用。在PET探测器中,由康普顿效应引起的晶体间散射现象会造成入射伽马光子的能量在多个位置通道沉积,给符合事件的甄别带来困难,从而影响PET系统的灵敏度和空间分辨率。为了改善晶体间散射事件对PET系统性能的影响,本文研究了晶体间散射事件的位置、能量和时间分布特征,并根据这些特征提出了基于能量值和时间差的晶体间散射事件第一作用点识别算法。文中从仿真和物理实验两个方面对晶体间散射事件进行研究,在仿真中使用基于Geant4的蒙特卡罗平台构建6×6通道硅酸钇镥(Lutetium-Yttrium Oxyorthosilicate,LYSO)晶体和硅光电倍增管(Silicon Photomultiplier,Si PM)一对一耦合的PET探测器,仿真晶体内康普顿效应过程,通过筛选得到沉积于伽马光子入射通道及周围八个通道的两通道响应晶体间散射事件。在物理实验中设计了与仿真中结构相同的PET探测器,使用高速示波器并设置识别条件获取同样位置的两通道响应晶体间散射事件。将获得的两通道响应晶体间散射事件的位置、能量和时间信息进行提取并对比分析,仿真和物理实验结果均表明两通道响应晶体间散射事件的位置、能量和时间分布具有明确的特征。基于晶体间散射事件的物理特征,文中对两通道响应晶体间散射事件中能量值和时间差的关系进行研究,根据研究结论提出了基于能量值和时间差的晶体间散射事件第一作用点识别算法。将该算法用于康普顿效应第一作用点所在位置通道的识别并进行了实验评估,结果显示该算法在第一作用点识别中具有84.1%的准确率,可使有效单事件计数率提高15.0%,对提高PET系统性能具有积极意义。更多还原

【Abstract】 PET is a functional imaging technology that can provide the biochemical reaction and metabolic information of tissues and organs in vivo and plays an important role in clinical diagnosis and drug development.In PET detector,the energy of gamma photons will be deposited in multiple channels because of the inter-crystal scattering phenomenon caused by the Compton effect,which can make it difficult to identify coincident events and has a negative effect on the sensitivity and spatial resolution in PET system.In order to improve this situation,the dissertation focuses on the position,energy and time distribution of intercrystal scattering events and proposes a method to find the position of first interaction in inter-crystal scattering events based on the information of energy and time difference.In this work,the inter-crystal scattering events will be studied in simulation and experiment.A 6×6 one-to-one coupled PET detector with LYSO and Si PM is constructed to simulate the process of inter-crystal Compton effect based on Geant4 in simulation,from which two-channel response inter-crystal scattering events deposited in the incident channel of gamma photons and eight channels around it are required.PET detector with the same structure as that in simulation is used to require two-channel response inter-crystal scattering events at the same position through high speed oscilloscope in experiment.Position,energy and time information of these two-channel response inter-crystal scattering events are extracted and analyzed.The results of simulation and experiment show that the position,energy and time distribution of these events have explicit characteristics.Based on the results of simulation and experiment,the relationship between energy and time difference in two-channel response inter-crystal scattering events is studied.According to the conclusion,a method based on energy and time difference is proposed to find the position of first interaction and the experiment shows that the accuracy is 84.1% and the number of valid events increases 15.0% with the method for two-channel response intercrystal scattering events,which has a positive effect for PET system.更多还原