基于瞬发伽马谱学的元素重建算法  

Prompt Gamma Spectroscopy Retrieval Algorithm for Element Measurements

作　　者：汪金龙 吴晓光[1] 杨立旺 赵子豪 郑云[1] 李聪博 李天晓 郑敏 WANG Jinlong;WU Xiaoguang;YANG Liwang;ZHAO Zihao;ZHENG Yun;LI Congbo;LI Tianxiao;ZHENG Min(Department of Nuclear Physics,China Institute of Atomic Energy,Beijing 102413,China)

机构地区：[1]中国原子能科学研究院核物理研究所,北京102413

出　　处：《中国无机分析化学》2024年第6期842-856,共15页Chinese Journal of Inorganic Analytical Chemistry

基　　金：国家自然科学基金资助项目(U1932209,11975315,U1867210,11905134);先导创新项目(LC192209000701,LC202309000201);持续基础科研项目(BJ20002501,WDJC-2019-13)。

摘　　要：质子治疗中的瞬发伽马射线是质子和靶标之间核反应的产物,瞬发伽马射线的特征能量和强度可以用来确定靶中元素的种类和数量,在之前的实验中已经证明,无论反应截面多么复杂,一旦确定了被照射元素和入射质子的能量,元素浓度与伽马射线光子数之间就存在一定的线性关系。然而,这种线性关系很难应用于医学成像,而且氢的非线性行为迄今尚未研究。将这种线性关系推广到包括氢等非线性情况的混合元素材料,并提出了一种通用的数学形式,即基于瞬发伽马谱学的重建算法(PGSRA)。PGSRA的基本假设是样品材料的PGS与元素的每摩尔伽马射线有某种关系。对于碳和氧,这种关系是线性的,而对于氢,这种关系是非线性的。由于2.23 MeV的伽马线来源于中子吸收辐射,研究氢非线性行为,利用蒙特卡罗模拟验证碳、氧和氢的不同组合,如聚甲基丙烯酸甲酯(PMMA)、戊二醇和乙醇二醇的线性和非线性关系。所有样品材料的碳、氧相对误差均小于4%。基于氢的非线性特性,其相对误差约为10%。此外,样品密度的相对误差对所有样品材料都小于3.5%。开发的PGSRA法可能是PGS和医学成像之间的第一座桥梁。Prompt gamma ray in proton therapy is the product of nuclear reaction between proton and target.The characteristic energies and intensities of prompt gamma lines can be used to determine the types of elements and their amounts in the target.In several previous experiments,it has been demonstrated that no matter how complex the reaction cross-section is,once the energy of the incident proton and the irradiated element are determined,there is a definite linear relationship between the element concentration and the number of gamma-ray photons.However,this linear relationship is difficult to apply to medical imaging and the nonlinear behavior of hydrogen has not been investigated to date.This linear relationship is extended to mixed elemental materials including nonlinear case such as hydrogen,and a universal mathematical form,which is referred to as the prompt gamma spectroscopy retrieval algorithm(PGSRA),is developed.The basic assumption of the PGSRA is that the PGS of the sample material has a relationship with the molar gamma lines of the elements.For carbon and oxygen,this relationship is linear,while for hydrogen,it is nonlinear.As the 2.23 MeV gamma line originates from neutron absorption radiation,the behavior of hydrogen is carefully investigated.The linear and nonlinear relationships are verified using Monte Carlo simulations with different combinations of carbon,oxygen,and hydrogen,such as PMMA,pentanediol and ethanediol.The relative errors of carbon and oxygen in all samples are less than 4% for all the sample materials.The relative errors of hydrogen,based on its nonlinear behavior,is approximately 10%.In addition,the relative errors of the sample density are less than 3.5% for all the sample materials.The PGSRA developed in this work could be the first bridge between PGS and medical imaging.

关 键 词：质子治疗 瞬发伽马谱学蒙特卡罗 FLUKA 中子吸收 

分 类 号：O657.35[理学—分析化学] TL99[理学—化学]