Monte Carlo track structure applications in microdosimetry and radiation response

蒙特卡罗轨道结构在微剂量测定和辐射响应中的应用

• 批准号: RGPIN-2015-04984
• 负责人: Enger, Shirin
• 金额: $ 1.38万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=650197
• 关键词: Monte; Carlo; track; structure; applications

In radiation therapy ionizing radiation is used to cause irreparable damage to the DNA and inhibit cell cycling of the cancer cells. Particle tracks superimposed on models of DNA indicate that damage occurs in clusters. These clustered DNA damages are the signature DNA lesion induced by ionizing radiation. The biological response to radiation is quantified in terms of the relative biological effectiveness (RBE), defined as the ratio between the absorbed dose of a reference radiation and that of a test radiation for a given biological endpoint. Low energy brachytherapy sources, proton and ion beams are associated with high RBE values. Numerous simulations of initial DNA damage suggest that the frequency distributions for ionisation or energy imparted in volumes representative of DNA segments are useful for considering radiation quality and for modelling biological damage produced by ionising radiation. ***Monte Carlo (MC) method is an accurate and rigorous tool to simulate radiation transport and score energy deposition in heterogeneous systems such as the human body. Track structure codes are a specific class of MC transport codes that can generate in detail the spatial pattern of energy deposit sites due to the event-by-event simulation of particle interactions. ******The aim of this proposal is to increase the knowledge about the mechanisms behind the varying RBE for different combinations of radiation and tumour cell types and normal tissues by studying in detail the ionization and excitation patterns caused by different radiation qualities, in order to gain the same confidence and control for low energy photon emitting brachytherapy sources, proton and particle therapy as for conventional radiation therapy. The analysis will be combined with observed radiation responses for different cell lines and radiation qualities, and an evidence based link between well-known and controlled physical beam properties and clinically observed radiation response parameterizations will be established. With such models in treatment planning, the clinicians can better choose and optimize the type of radiation and dose distribution for each patient. ***Aim A: Use methods developed in an earlier study to investigate if the microdosimetric variation of energy imparted per cell, due to the different size of the cells and their nuclei within a tissue sample, have an impact on experimentally determined cell survival curves and tumour control probability. ***Aim B: Develop and use track structure codes to search for a relationship between frequency distribution of order of clusters of energy deposit sites, as a descriptor of radiation impact, and RBE for cell survival for various radiation qualities. A method for predicting RBE values for low energy photons, protons and other ions on the basis of dose-response data obtained from photons will be developed and included in radiation therapy treatment plans. **

在放射治疗中，电离辐射被用来对DNA造成不可修复的损伤，并抑制癌细胞的细胞循环。叠加在DNA模型上的粒子轨迹表明，损伤是成群发生的。这些聚集性DNA损伤是电离辐射引起的典型DNA损伤。对辐射的生物反应是用相对生物有效性（RBE）来量化的，相对生物有效性的定义是参考辐射的吸收剂量与给定生物终点的测试辐射的吸收剂量之间的比率。低能量近距离治疗源，质子和离子束与高RBE值有关。对初始DNA损伤的大量模拟表明，电离频率分布或以DNA片段为代表的体积所传递的能量对于考虑辐射质量和模拟电离辐射产生的生物损伤是有用的。蒙特卡罗（MC）方法是一种精确而严谨的工具，用于模拟辐射传输和记录非均匀系统（如人体）中的能量沉积。轨迹结构代码是一类特殊的MC传输代码，通过对粒子相互作用的逐次模拟，可以详细地生成能量沉积点的空间格局。******本建议的目的是通过详细研究不同辐射质量引起的电离和激发模式，增加对不同辐射组合与肿瘤细胞类型和正常组织不同RBE背后机制的了解，以便获得与传统放射治疗相同的低能量光子发射近距离治疗源，质子和粒子治疗的信心和控制。该分析将与观察到的不同细胞系和辐射质量的辐射反应相结合，并在已知和受控的物理光束特性与临床观察到的辐射反应参数化之间建立基于证据的联系。利用这些模型进行治疗计划，临床医生可以更好地选择和优化每个患者的放疗类型和剂量分布。***目的A：使用在早期研究中开发的方法来研究由于组织样本中细胞及其细胞核大小的不同，每个细胞传递的能量的微剂量变化是否对实验确定的细胞存活曲线和肿瘤控制概率有影响。***目标B：开发并使用轨道结构代码来寻找能量沉积点簇序的频率分布（作为辐射影响的描述符）与各种辐射质量下细胞存活的RBE之间的关系。将开发一种基于从光子获得的剂量反应数据预测低能光子、质子和其他离子的RBE值的方法，并将其纳入放射治疗计划。**