肺癌放射治疗中危及器官保护关键问题研究

发布时间：2018-03-24 08:22

本文选题：肺癌　切入点：几何不确定性　出处：《中国科学技术大学》2017年博士论文

【摘要】：放射治疗已经成为治疗各分期肺癌的主要手段之一。如何减少危及器官受照剂量或对其受照剂量进行准确评估是当今肺癌放射治疗中的重要研究内容。肺部肿瘤放疗过程中依旧存在较多导致危及器官受照剂量增加或难以准确评估的问题,如外放临床靶区产生的危及器官受照剂量增加问题、治疗方案的优化选择问题以及中心型肺癌立体定向治疗过程中肿瘤体积或身体解剖结构等变化问题。本文围绕上述问题进行了深入研究,主要研究内容与创新之处包括:(1)研究阐释了基于几何不确定性的肺部危及器官剂量学特征。在分析图像引导放射治疗中随机误差和系统误差特点的基础上,对基于几何不确定性的危及器官剂量学特征进行了深入研究。用临床靶区几何不确定性模型代替对临床靶区外放,并将其作为目标函数放在优化阶段考虑。通过比较该方法同传统外放方式剂量学的差异,结果表明该方法在肺癌放疗中可有效减少危及器官辐射剂量且简单快捷,具有一定应用潜力。同时,通过分析随机和系统两种误差对肿瘤靶区与危及器官剂量的影响,结果表明容积旋转调强计划执行过程中肺等危及器官剂量分布对两类几何不确定性均较敏感。(2)提出了肺瘤比的评价指标,给出了多种典型治疗技术下肺瘤比同肺部剂量之间的幂函数关系。为解决因肺癌患者之间肺部体积、肿瘤体积及位置等个体差异较大造成的最佳治疗方案选择难题,提出了肺瘤比的概念,深入分析了多种典型治疗技术下肺瘤比同肺部剂量之间的关系。通过评估比较发现在不同放疗技术中肺瘤比同肺部平均剂量之间具有不同的幂函数关系。同时,通过自适应放疗过程中的肿瘤体积变化同肺部平均剂量变化特征对二者之间的关系进行了测试验证。结果表明,肺癌患者的肺瘤比大小对治疗方案选择具有参考意义。(3)研究发现中心型肺癌自适应SBRT治疗中混合形变配准可以有效减小锥形束计算机断层扫描图像散射的影响。中心型肺癌在立体定向放射治疗过程中常存在肿瘤体积或身体结构的变化,会造成危及器官受照剂量难以精确评估的问题。通过对基于锥形束计算机断层扫描及混合形变配准的剂量跟踪技术进行测试验证,结果表明混合形变配准可以有效减小锥形束计算机断层扫描图像散射的影响,耦合混合形变配准与锥形束计算机断层扫描的剂量追踪技术可以对危及器官和靶区剂量进行精确评估,可以避免不必要的辐射损伤及靶区漏照射。
[Abstract]:Radiation therapy has become one of the main methods in the treatment of lung cancer at various stages. How to reduce the radiation dose to the organ or evaluate the radiation dose accurately is an important research content in the radiotherapy of lung cancer. In the course of radiotherapy, there are still many problems that lead to the increase of radiation dose or the difficulty of accurate assessment. In the case of an increase in the radiation dose to the organ endangered by the outputting of the clinical target area, The optimization of treatment scheme and the changes of tumor volume or anatomical structure during stereotactic treatment of central lung cancer are discussed in this paper. The main research contents and innovations include: (1) the study explains the dosimetric characteristics of lung organ hazards based on geometric uncertainty. On the basis of analyzing the characteristics of random error and systematic error in image-guided radiation therapy, In this paper, the dosimetric characteristics of hazardous organs based on geometric uncertainty are studied in depth. The clinical target geometric uncertainty model is used to replace the clinical target extrapolation. By comparing the difference between this method and the traditional radiation dosimetry, the results show that this method can effectively reduce the radiation dose of organ in lung cancer radiotherapy and is simple and fast. At the same time, by analyzing the effects of random and systematic errors on tumor target and organ dose, The results show that the dose distribution of lung and other dangerous organs is more sensitive to the two kinds of geometric uncertainties during the implementation of the volume rotation intensity modulation plan. The power function relationship between lung tumor ratio and lung dose is given in this paper. In order to solve the problem of choosing the best treatment scheme caused by the large difference of lung volume, tumor volume and location among lung cancer patients. The concept of lung tumor ratio is put forward. The relationship between the lung tumor ratio and the lung dose under various typical treatment techniques is analyzed in depth. It is found that there is a different power function relationship between the lung tumor ratio and the lung average dose in different radiotherapy techniques. The relationship between the changes of tumor volume and lung mean dose during adaptive radiotherapy was tested and verified. The lung tumor ratio of lung cancer patients has reference significance for the choice of treatment scheme. The study shows that the mixed deformation registration in the treatment of central lung cancer with adaptive SBRT can effectively reduce the effect of cone-beam computed tomography image scattering. During stereotactic radiotherapy, central lung cancer often has changes in tumor volume or body structure. It can lead to the difficulty of accurate assessment of the radiation dose to the organ at risk. A dose tracking technique based on conical beam computed tomography and mixed deformation registration is tested and verified. The results show that mixed deformation registration can effectively reduce the effect of conical beam computed tomography image scattering. The dose tracing technique coupled with mixed deformation registration and conical beam computed tomography can accurately evaluate the dose of the endangered organs and target areas and avoid unnecessary radiation damage and target leakage.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：R734.2;R730.55

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