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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=613292
• 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，电离辐射用于对DNA造成不可修复的损伤并抑制癌细胞的细胞周期。叠加在DNA模型上的粒子轨迹表明，损伤是以簇的形式发生的。这些成簇的DNA损伤是电离辐射诱导的标志性DNA损伤。对辐射的生物反应用相对生物有效性（RBE）来量化，RBE定义为给定生物学终点的参考辐射吸收剂量与测试辐射吸收剂量之间的比率。低能量近距离放射治疗源、质子和离子束与高RBE值相关。初始DNA损伤的许多模拟表明，在代表DNA片段的体积中赋予的电离或能量的频率分布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格的工具，可以模拟辐射在非均匀系统（如人体）中的传输和能量沉积。径迹结构代码是一类特殊的MC输运代码，由于粒子相互作用的逐事件模拟，它可以详细地生成能量存款站点的空间模式。 该提案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，增加对辐射和肿瘤细胞类型和正常组织的不同组合的不同RBE背后机制的了解，以便获得与常规放射治疗相同的低能量光子发射近距离放射治疗源、质子和粒子治疗的置信度和控制。该分析将与观察到的不同细胞系和辐射质量的辐射响应相结合，并将建立众所周知的和受控的物理射束特性与临床观察到的辐射响应参数化之间的循证联系。在治疗计划中使用这些模型，临床医生可以更好地选择和优化每个患者的辐射类型和剂量分布。 目标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的不同大小而赋予每个细胞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产生影响。 目标B：开发并使用轨道结构代码，以搜索作为辐射影响描述符的能量存款位点簇的顺序的频率分布与各种辐射质量的细胞存活的RBE之间的关系。将开发一种根据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。