四种治疗计划系统中靶区边界外扩算法应用的比较研究

The Comparison of Margining Algorithms Applied in Four Commercial Treatment Planning Systems

目的:对比分析目前国内临床常用的四种治疗计划系统所使用的边界外扩算法在外扩体积上的差异,以及在剂量学上的影响。方法:选取四种治疗计划系统对于同一临床病例中相应的临床靶区进行3 mm和5 mm的全向外扩,比较分析外扩后形成的PTV体积差异;采用与临床实施时完全一致的计划条件设置参数,统计总的机器跳数以及各剂量覆盖体积的差异。结果:四种治疗计划系统采用的边界外扩算法对于相同体积的外扩结果均不相同,Xio治疗计划系统采用边界外扩算法对于靶区外扩后的体积最小,与Monaco系统近似,Pinnacle治疗计划系统对于靶区的外扩体积最大,Eclipse治疗计划系统外扩靶区体积略小于Pinnacle系统。在剂量学方面,所需总的机器跳数无显著区别,但是相同剂量所覆盖的面积不同,与外扩体积大小成正比。结论:四种治疗计划系统对于相同临床靶区外扩成计划靶区体积是不同的,因此造成了正常组织的可能接受了不必要的高剂量照射或靶区漏照。

Objective： To evaluation the differences in volume for planning target produced by margining algorithms applied in four commercial treatment planning systems and effect on dosimetry. Methods： Four commercial treatment planning system were used to produce planning target volume（PTV） from clinic target volume（CTV） with a uniform margin of 3mm and 5mm. And all the CTVs and PTVs were imported into Pinnacle for volume calculation and comparison. The total monitor units and volumes covered by 95% of prescription dose from same treatment plan were compared for four margining algorithms. Results： The deviation existed in PTV volumes for four margining algorithms. The volume of PTV expanded from Pinnacle is the great- est one in all and the one from Xio system is the smallest in all. The volume of PTV expanded from Eclispe is the greater than one from Monaco system. The total monitor units haven＇t a great difference because little deviation existed in field size. The volumes covered by 95% prescription dose have a little deviation and relatively to the volume of PTV. Conclusions： We have found significant difference in the three dimensional margin algorithms. And inaccurate margin algorithms have a potential probability to add extra unnecessary dose to normal tissue or make planning target lack of enough prescription dose.