基于Monaco计划系统的最小子野面积设置值对宫颈癌调强放疗计划的影响

The influence of the minimum subfield area setting value based on the Monaco planning system on the intensity-modulated radiotherapy plan for cervical cancer

目的探究基于Monaco计划系统的最小子野面积(MSA)在宫颈癌静态调强放疗计划中的最优设置值,以提高宫颈癌放疗计划精确性。方法回顾性收集10例宫颈癌患者,使用Monaco治疗计划系统设计固定五个射野静态调强计划,MSA分别为1、2、4、10、20、50、80和100 cm^(2),每个患者得到8个放疗计划。以MSA为2 cm^(2)的放疗计划为对照组,比较其他MSA设置值的放疗计划,在其他优化目标函数和约束条件相同前提下,只改变MSA设置值,利用方差分析和事后比较的统计学方法来研究MSA对放疗计划产生的影响。结果当MSA在10~20 cm^(2)范围内,与对照组相比,靶区和危及器官的剂量变化不明显,但是机器跳数和子野数目开始下降。当MSA从50 cm^(2)开始,与对照组相比,靶区内最大剂量(D 2%)和平均剂量(D_(mean))均增加,均匀性指数(HI)和适形性指数(CI)开始变差。除了小肠平均剂量D_(mean)随MSA变化不大外,其余危及器官受量都随着MSA增大而不同程度地增加(P<0.05);机器跳数和子野数目总体随着MSA增大而减少。结论在基于Monaco治疗计划系统宫颈癌静态调强计划的设计中,MSA设置值的最佳范围为10~20 cm^(2)。

Objective To investigate the optimal setting value of the minimum segment area(MSA)based on the Monaco planning system in the static intensity modulated radiotherapy(IMRT)plan for cervical cancer to improve the accuracy of radiotherapy planning for cervical cancer.Methods A retrospective collection of 10 patients with cervical cancer was performed using the Monaco treatment planning system to design fixed five-field static intensity modulation plans with MSA of 1,2,4,10,20,50,80,and 100 cm^(2).Each patient received eight radiotherapy plans.The radiotherapy plan with an MSA of 2 cm^(2)was used as the control group to compare the radiotherapy plans with other MSA settings.Under the premise that other optimization objective functions and constraints were the same,only the set value of MSA was changed,and the statistical methods for analyzing of variance and post-hoc comparison were used to study the impact of MSA on radiotherapy plans.Results When MSA was in the range of 10~20 cm^(2),compared with the control group,the dose of target area and organ-at-risk did not change significantly,but the number of monitor units and subfields began to decrease.When MSA starts from 50 cm^(2),compared with the control group,the maximum dose(D2%)and the average dose(D_(mean))in the target area both increased,and the uniformity index(homogeneity index,HI)and conformity index(conformity index,CI)began to deteriorate.Except for the small intestine average dose(D_(mean))that changed slightly with MSA,the exposure to other organs at risk increased with the increase of MSA(P<0.05);the number of monitor units and subfields generally decreased with the increase of MSA.Conclusion In the design of a static intensity modulation plan for cervical cancer based on a Monaco treatment planning system,the optimal setting range for the MSA setting value is 10~20 cm^(2).