摘要
目前调强放射治疗计划设计主要有两种方式:一种是基于射束元方式的分步法,即先优化得到射野剖面的强度分布、再据此优化生成子野;另一种是子野直接优化的方法,该法直接用多叶准直器叶片位置及叶片运动参数作为为子野优化参数进行优化计算。本文通过一个模拟例子和一个临床实例对这两种设计方式进行研究,以进一步分析设计方式不同对治疗计划结果的影响。通过对两种具体的不同设计方式下各病例的治疗计划的比较得到了与现有文献完全相反的结论,经分析认为现有文献中关于两种设计方式的比较结论值得商榷,二者的比较应以选择合适的设计流程为前提。同时发现,基于子野直接优化方式的结果对多叶准直器初始叶片位置有较强依赖性;另外,采用本文所采用的基于射束元方式的调强放射治疗过程,将不需要考虑强度的平滑化处理,由该方式产生的子野中有相当比例可以忽略而被舍弃,但对小子野仍需要慎重对待,不可随意删除,子野直接优化方式中之所以存在子野数目需求问题,很大程度上也是由于小子野被忽略;此外,对于子野的权重优化需要选择合适的优化算法。因此自动生成子野的算法值得进一步研究;基于分布法的设计方式在如何选择合适的分群强度级和如何筛选子野的问题上也值得进一步研究;对于一个优秀的治疗计划系统,应该具备两种调强放射治疗计划设计方式,在临床应用上,应根据具体情况,选择合适的设计方式。
At present, intensity modulated radiation therapy （IMRT） technology includes two main design modes： multi-step （MS） mode based on beam element method and direct aperture optimization （DAO） mode. The intensity distribution of field profile is obtained and then optimized into segments by MS, while the DAO takes the leaf position of multi-leaf collimator and leaf motion parameters as the segment optimized parameters to do the optimization calculation. By comparing the dose distribution of one simulated example and one clinical example applying the two modes respectively to further analyze the effects of different treatment plans. And the comparative results were different from the present literature, so the comparative results of present literature need to be reconsidered, and the comparison should be base on the appropriate process for design. DAO had a strong dependence on the initial leaf position of multi-leaf collimator. Besides, the smoothing of intensity was not necessary for MS mode. A percentage of the segments obtained by MS mode could be ignored and abandoned, however, small segments still need to be considered. The demand for the number of segments in DAO mode mainly because of the ignored small segments. An appropriate optimization algorithm should be selected to do the weight optimizing of segments, so the algorithm to automatically generate segments is worthy of researching. And based on the MS, the appropriate clustering intensity level and segments worth further exploring. A excellent IMRT planning system should consist of the two modes at the same time, and an appropriate design method should be selected for different conditions.
出处
《中国医学物理学杂志》
CSCD
2015年第3期391-396,共6页
Chinese Journal of Medical Physics
基金
新疆师范大学理论物理自治区重点学科项目资助
关键词
调强放射治疗
子野直接优化
多叶准直器
分布设计法
intensity modulated radiation therapy （IMRT）
direct aperture optimization （DAO）
multileaf collimator
multistep （MS） mode
