调强放射治疗笔形束算法研究

目的：探讨笔形束算法的原理应用于调强放射治疗计划的临床物理数据，参数修正方法。方法i对有限元笔形束算法的计算模型进行分析利用蒙特卡罗算法对利用大野数据推导的有限元笔形束算法数据进行对照分析，采用有限元笔形束算法的计算误差进行验证。结果：有限元笔形束算法模型得到的数据与测量数据对比，PDD数据有很好匹配，误差〈2％；Profiles数据在半影区域和射野边缘区域最大达到4％。利用大野线性关系得到的小射野输出因子与MonteCarlo算法得到的输出因子具很好的一致性。结论：以有限元笔形束算法模型为基础的调强放射治疗计划系统在临床剂量计算中能得到较好的精度，可提高计算速度。利用大野数据推导的小野输出因子，可以代替用Monte Carlo算法得到的射野输出因子。

The algorithm study of the IMRT based on pencil beam model

Objective：To discuss the principle of algorithn in intensity modulated radiotherapy and how to adjust some measured data to match calculated model. Methods： Through adjusting some calculation parameters to match the calculated data of algorithms on Montel Carlo, those data were compared to verify the accuracy of FPBM algorithm. And by measuring big regular fields data to get small beam fields （〈4cm） data, these data were compared with data of Montel Carlo algorithm. Results： The calculated pentage depth dose agreed with the easements within ± 2% between measured data and data based on FPBM, and the beam profiles agreed with the measurements within ± 4%. By measuring big regular fields data to get small beam fields （ 〈 4cm^2 ） data, these data were good consistent compared with data of Montel Carlo algorithm. Conclusion ： Based on FPBM algorithm, the IMRT planning system can provide faster results and better precision dose. And these data which were calculated form big regular beams would get a good consistent with data based on Montel Carlo algorithm.