氡子体多尺度剂量学方法研究与应用

发布时间：2018-01-24 12:03

本文关键词： 氡子体呼吸道模型精细剂量分布细胞剂量　出处：《清华大学》2016年博士论文　论文类型：学位论文

【摘要】：氡是最重要的天然辐射源之一,其辐射危害一直是辐射防护领域研究的热点问题。目前,对于氡辐射所致健康效应的研究方法主要有流行病学调查和放射生物学实验,两种方法的结果都依赖于剂量估算的准确性。因此开发出能更精细、准确反映人体呼吸道解剖学结构的氡子体剂量学模型对于研究氡辐射是十分必要的。本论文基于氡辐射的物理原理,对环境中氡子体进入人体后,在呼吸道沉积、廓清,同时发生衰变放出α粒子,能量沉积在辐射敏感细胞的整个过程进行研究,并对可能造成的辐射健康影响进行探讨。具体完成工作如下:1.精细化呼吸道模型的建立。本文以中国参考人呼吸道模型为基础,根据支气管解剖学参数,采用数学建模结合体素化的方法建立了国际上首个具备连续16级支气管分叉结构的呼吸道体素模型。该模型完整地反映了整个肺部的气管及各级支气管结构,是本文剂量计算的基础;本文提出的参数化模型构造方法也为将来个体化剂量计算提供了可能。2.生物动力学研究。采用沉积模型和廓清模型分别计算得到氡子体气溶胶在呼吸道各个区域的初始沉积份额以及发生转移、吸收入血后的核素活度。并使用流体力学软件对氡子体在支气管区的运动过程进行了模拟,计算得到粒子的三维沉积分布,从而为剂量计算提供放射性源粒子分布数据。3.剂量学计算。利用精细呼吸道模型和源粒子沉积分布,计算在源粒子非均匀分布情况下的氡子体剂量转换系数。同时,统计每个靶体素中的能量沉积,建立了高解析度的呼吸道三维剂量分布,为剂量热点及其辐射效应分析提供依据。在此基础上,在最大剂量体素内建立靶细胞模型,得到支气管壁上辐射敏感细胞可能受到的最大吸收剂量,从而将剂量研究推进到细胞水平。4.精细剂量分布的应用。辐射剂量在呼吸道的精细分布可以为进一步的辐射损伤、致癌风险研究提供翔实准确的依据。本文对两种典型应用做探讨性分析。一方面,对典型条件下氡子体致肺癌的风险进行评估,对剂量分布与癌症发生率的关系进行了探讨。另一方面,应用于异常高氡地区的结果表明,在某些极端情况下,氡子体所致呼吸道剂量会超过细胞死亡准阈剂量,可能导致部分细胞死亡,这是以往辐射风险研究中没有考虑过的因素。
[Abstract]:Radon is one of the most important natural radiation sources, its radiation damage has been a hot issue in the field of radiation protection. The main research methods for the health effects of radon radiation are epidemiological investigation and radiobiological experiments. The results of both methods depend on the accuracy of dose estimation. A dosimetric model of radon progeny which accurately reflects the anatomical structure of human respiratory tract is necessary for the study of radon radiation. In the respiratory tract deposition, clearance, at the same time decay and release of alpha particles, energy deposition in the whole process of radiosensitive cells were studied. And the possible health effects of radiation were discussed. The detailed work is as follows: 1. The establishment of elaborate respiratory tract model. This paper based on the Chinese reference human respiratory tract model, according to the parameters of bronchial anatomy. The first international airway voxel model with continuous 16 grade bronchobranching structure was established by mathematical modeling combined with voxinization. The model reflects the trachea and bronchi structure of the whole lung completely. It is the basis of dose calculation in this paper. The parameterized model construction method proposed in this paper also provides the possibility of individualized dose calculation in the future. 2. Biodynamic study. The radon daughter aerosol in respiratory tract was calculated by sedimentation model and clearance model, respectively. The initial depositional share of the area and its transfer. The radionuclide activity was absorbed into the blood, and the motion process of radon progeny in the bronchial region was simulated by hydrodynamic software, and the three-dimensional deposition distribution of the particles was calculated. Thus, the radioactive source particle distribution data. 3. Dosimetric calculation. Using the fine respiratory model and source particle deposition distribution. The dose transfer coefficients of radon progeny were calculated under the condition of heterogeneous distribution of source particles. At the same time, the energy deposition in each target element was counted, and the high resolution three-dimensional dose distribution of respiratory tract was established. On the basis of this, the target cell model was established in the maximum dose voxel, and the maximum absorbed dose of radiosensitive cells on the bronchial wall was obtained. The application of fine dose distribution. The fine distribution of radiation dose in the respiratory tract can be further radiation damage. The study of carcinogenic risk provides accurate and accurate basis. This paper makes an exploratory analysis of two typical applications. On the one hand, the risk of lung cancer caused by radon progeny under typical conditions is evaluated. The relationship between the dose distribution and the incidence of cancer is discussed. On the other hand, the results of the application in the regions with abnormally high radon show that in some extreme cases. The respiratory dose caused by radon progeny may exceed the quasi-threshold dose of cell death, which may lead to the death of some cells, which has not been considered in the previous radiation risk studies.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：R818

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