子野分割算法对剂量分布和计划执行效率的影响

目的：比较Elekta XIO TPS（版本：4.70）2种子野分割算法分别为SLD和SMT对剂量分布和计划执行效率的影响.方法：选取9例鼻咽癌患者进行调强计划逆向优化生成射野通量分布图,改变子野分割算法的有关参数产生不同的子野序列.SLD算法,最小子野边长取1cm、2cm、3cm产生3组子野序列,强度分层等级取6、8、10、12、15产生5纽子野序列;SMT算法,最小子野面积取2cm2、4cm2、6cm2产生3组子野序列,子野抑制因子取3、5、7产生3组子野序列.对14组子野序列计算得到的剂量分布进行相关剂量学参数的对比分析,考虑机器跳数及子野总数等因素综合评价.结果：（1）最小子野边长和最小子野面积对靶区剂量分布和计划执行效率影响较大,有统计学意义（P＜0.05）.（2）强度分层等级和子野抑制因子对靶区剂量分布和计划执行效率影响较小,有统计学意义（P＜0.05）,前者取值超过10以后,评价指标除子野总数外,其余变化不明显,差异无统计学意义（P＞0.05）.（3） SMT算法产生的子野总数约为SLD算法的90％,靶剂量分布更优,有统计学意义（P＜0.05）.结论：（1）最小子野边长和最小子野面积为粗调,对剂量分布影响较大;强度分层等级和子野抑制因子为细调,对剂量分布影响较小,且达到某一特定值后趋于稳定.（2） SMT算法相比SLD算法生成的子野总数更少且剂量分布更优.

The Effects of Segment Algorithm on Dose Distribution and Plan Execution Efficiency

Objective： To compare the effects of two segment algorithms of SlidingWnd and SmartSequencing used in Elekta XIO TPS （Version ： 4. 70） on the Dose Distribution and Plan Execution Efficiency. Methods： 9 patients with nasopharyngeal carcinoma were selected for the study. First of all, generated beam＇ s intensities for each patient by reverse optimization of IMRT plan; In the second, the different segments for each beam were created by changing the relative parameters of two segment algorithms. The Sliding- Wnd algorithm, 3 groups of segments were created by means of the Minimum -segment -size setted lem, 2cm, 3cm and 5 groups of segments by the Discrete -intensity -levels setted 6, 8, 10, 12, 15. The SmartSequencing algorithm, 3 groups of segments werecreated by means of the Minimum - segment - area setted 2cnr2, 4cm2, 6cm2and the other 3 groups of segments by the Segment - suppression -factor setted 3, 5, 7. At last, compared the relative dosimctry differences which 14 groups of segments calculated to ac- quire, In addition, evaluate the factors of Machine Units and Segment number. Results： 1. The Minimum - segment - size and Mini- mum - segment - area has a great Effects on Dose Distribution and Plan Execution Efficiency, the differences were significant （ P 〈 0. 05 ） . 2. The Discrete - intensity - levels and Segment - suppression - factor has a little Effects on Dose Distribution and Plan Exe- cution Efficiency, the differences were significant （P 〈 0. 05 ）, the value of the former were setted more than 10, in addition to the seg- ment number, the change of the rest evaluation index is not obvious, and the differences were not significant （P 〉 0. 05） . 3. Com- pared with the SlidingWnd algorithm, the SmartSequencing algorithm could reduce the segment number by 10% and acquire better dose distribution, the differences were significant （ P 〈 0. 05 ） . Conclusions： 1. The factors of Minimum - segment - size and Minimum - segment - area have a great Effects on Dose Distributi