组织不均匀条件对调强计划系统计算模型精度影响的研究

发布时间：2018-05-23 18:39

本文选题：调强放疗 + 蒙特卡罗方法　；参考：《清华大学》2012年硕士论文

【摘要】：三维调强放射治疗技术已经在临床中得到广泛应用。但是由于人体组织结构的复杂性，和IMRT治疗计划的复杂性影响，，不同剂量算法的治疗计划系统在计算的IMRT治疗计划剂量分布时计算会有不同的误差存在。验证不同算法在不同条件下的剂量精度，对选择合适的系统和适应症，保证治疗的剂量误差没有超出临床允许的范围，是IMRT治疗成败的关搖问题之一。本课题研究了在组织不均匀条件下，商业化的治疗计划系统（MONACO）中的有限笔形束（FSPB）算法与快速X射线体积元蒙特卡罗（XVMC）算法的IMRT计划计算精度差别，以及它们对临床治疗的影响和各自的应用范围。课题实验首先对MONACO计划系统两种算法在均匀模体中输出的二维平面剂量及绝对剂量分别用二维半导体阵列和指型电离室进行了测量比对。在非均匀仿真人体模型中，对两种算法模型计算的规则照射野及调强照射野的剂量精度利用经过刻度的放射性铬胶片（EBT2）进行剂量测量比对。了解系统对6MV和15MV能量的X射线在仿真人体模型中肺、骨以及软组织各部分结构的剂量计算误差。实验结果显示：1、在均匀等效固体水模体中，对6MV和15MV能量的射线，XVMC算法计算结果与实际测量的值误差均在±2%范围内，而FSPB算法计算结果与实际测量值的误差均在±3%范围内。利用二维半导体阵列验证两种算法在均匀模体中计算的IMRT计划，其GAMMA通过率（3mm，3%）均大于90%，指型电离室测量绝对剂量XVMC算法偏差-0.66±1.55%，FSPB算法偏差1.67±1.71%。2、在非均匀仿真人体模型中，不同能量的X射线规则照射野，XVMC算法在不同介质中的剂量计算与胶片测量的结果偏差均在±2%范围内，而FSPB计算的结果与测量结果的偏差除了15MV能量2cm×10cm射野情况下肺中的剂量偏差高达6.51%以外，其他条件下的结果偏差也都在±3%范围内。IMRT计划的胶片验证测量结果中，Gamma（3%/3mm）通过率XVMC算法组大于90%；FSPB算法组小于90%大于80%，且Gamma（4%/4mm）通过率大于90%；而两种算法的3mm等剂量距离误差（DTA）的通过率均大于90%。研究的结论为：当临床治疗病例的组织密度不均匀性较大、子野数较多的情况下， XVMC算法的剂量计算精度优于FSPB算法，采用XVMC治疗设计胸腹部IMRT治疗计划可以将算法所引起的误差控制在3%以内。
[Abstract]:Three-dimensional intensity modulated radiotherapy has been widely used in clinical practice. However, due to the complexity of human tissue structure and the complexity of IMRT treatment plan, there are different errors in the calculation of dose distribution of IMRT treatment plan by different dose algorithms. It is one of the key problems for the success or failure of IMRT to verify the dose accuracy of different algorithms and ensure that the dose error of the treatment does not exceed the clinical allowable range for the selection of appropriate system and indications. In this paper, the difference of IMRT planning accuracy between the finite pencil beam (FSPB) algorithm and the fast X-ray volume element Monte Carlo (XVMC) algorithm in the commercialized treatment planning system (MONACOO) is studied under the condition of uneven organization. And their effects on clinical treatment and their respective application scope. Firstly, the two-dimensional plane dose and absolute dose of MONACO planning system in uniform mode are measured and compared with that of two-dimensional semiconductor array and digital ionization chamber, respectively. In the non-uniform simulated human body model, the dose accuracy of the regular irradiation field and the intensity modulated radiation field calculated by the two algorithms are compared by using the calibrated radioactive chromium film EBT2. To understand the dose calculation errors of the lung, bone and soft tissue components of 6MV and 15MV energy X-ray in the simulated human model. The experimental results show that in the homogeneous equivalent solid water mode, the error between the calculation results of 6MV and 15MV energy and the measured values is in the range of 卤2%, while the error between the calculated results of the FSPB algorithm and the actual measured values is within 卤3%. Two dimensional semiconductor array was used to verify the IMRT plan calculated by the two algorithms in the homogeneous mode. The GAMMA pass rate of the two algorithms was higher than 90. The deviation of the absolute dose XVMC algorithm measured by the finger ionization chamber was -0.66 卤1.550.67 卤1.71. 2. In the non-uniform simulation of human body model, the deviation of the two algorithms was 1.67 卤1.71. The deviation between the dose calculation of the XVMC algorithm and the film measurement in different media is in the range of 卤2%. The deviation between the results of FSPB calculation and that of measurement was 6.51% in the case of 15MV energy 2cm 脳 10cm field. Under other conditions, the deviation of results is also in the range of 卤3%. IMRT plan. The result of film verification measurement is Gamma3 / 3mm) pass rate XVMC algorithm group is greater than 90% more than 90% FSPB algorithm group > 80%, and Gamma-4 / 4 mm) pass rate is greater than 90%; and the 3mm equal dose distance of both algorithms is greater than 90%. The pass rate of DTAs is more than 90%. The conclusions are as follows: when the tissue density and the number of subfields are large, the dose calculation accuracy of XVMC algorithm is better than that of FSPB algorithm. The error caused by the algorithm can be controlled within 3% by using XVMC to design the IMRT treatment plan of chest and abdomen.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R311

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