Eclipse治疗计划系统NTO优化工具在脊柱转移瘤立体定向放疗靶区外剂量跌落研究

Study of NTO Tool with Eclipse System in Dose Fall-off Outside the Target of Stereotactic Body Radiation Therapy for Spine Metastasis

关键词:  脊柱转移瘤  正常组织目标优化工具  梯度指数  立体定向放射治疗  治疗计划系统

Key words:  spine metastasis  normal tissue objective optimization tools  gradient index  stereotactic body radiation therapy  treatment planning system

摘要:

为研究Eclipse治疗计划系统中正常组织目标(Normal Tissue Objective，NTO)优化工具参数，对脊柱转移瘤立体定向放射治疗计划靶区覆盖剂量和靶区外剂量跌落梯度指数(Gradiet Index，GI)的影响，本研究对10例脊柱转移瘤立体定向放射治疗患者设计两种类型计划。第1种添加NTO优化工具但不添加环优化条件，共得到360个计划，为参考计划；第2种添加环优化条件但不添加NTO优化条件，总共10个计划，为标准计划。所有计划最后剂量归一为100%处方剂量覆盖90%靶区体积。比较两种类型计划的靶区剂量适形度指数(Conformity Index,CI)、靶区外剂量跌落梯度指数、靶区最大剂量(D_max)、实际治疗时间和计划临床合格率。结果表明，当NTO优化工具参数Fall-off为0.5或者1，Priority为500、700和999时，计划的GI值相似(P>0.05)，但是小于其他Fall-off和Priority的GI值(P<0.05)；Fall-off和Priority对CI值大小和实际治疗时间没有影响(P>0.05)；随着Priority增加，计划靶区体积(Planning Target Volume，PTV) D_max增加(P<0.05)。参考计划的临床合格率最高为70%。与标准计划相比，最合适NTO优化工具参数计划(Priority、Fall-off分别为500和0.5)的GI值更低(3.449 vs 3.655，P=0.000，Z=-5.534)，实际治疗时间没有差异(2.65 min vs 2.32 min，P=0.063，Z=0.832)，PTV D_max偏大(132.1% vs 128.8%，P=0.002，Z=4.214)，CI偏大(0.911 vs 0.879，P=0.151，Z=0.984)。综上所述，在计划可通过情况下，当NTO优化工具中参数Distance from Target Border设置为0.2 cm，Start Dose设置为91%处方剂量，End Dose设置为49.4%处方剂量，Fall-off和Priority分别设置为0.5和500时，脊柱转移瘤立体定向放疗计划能够实现较好的靶区剂量适形度、更低的剂量梯度指数以及合适的治疗时间。

Abstract:

In order to study the effects of Normal Tissue Objective (NTO) optimization tool parameters in Eclipse treatment planning system on target coverage dose and dose drop Gradient Index (GI) outside target volume in Stereotactic Body Radiotherapy Therapy (SBRT) for spinal metastases,two types of plans were designed for 10 patients with spinal metastases treated with SBRT.The first one adds NTO optimization tool but does not add loop optimization conditions,and a total of 360 plans are obtained,which are reference plans.The second one adds loop optimization conditions but does not add NTO optimization conditions.There are 10 plans in total,which are standard plans.The final dose of all plans is normalized to 100% prescription dose covering 90% of the target volume.The target dose Conformity Index (CI),the dose drop GI,the maximum dose (D_max),the actual treatment time and the planned clinical qualification rate of the two types of plans were compared.The results show that when the NTO optimization tool parameter Fall-off is 0.5 or 1,the Priority is 500,700 and 999,the GI value of the plan is similar (P>0.05),but smaller than other Fall-off and Priority GI values (P<0.05).Fall-off and Priority have no effect on CI value and actual treatment time (P>0.05).With the increase of Priority,the Planning Target Volume (PTV) Dmax increases (P<0.05).The highest clinical qualified rate of the reference plan was 70%.Compared with the standard plan,the GI value of the most suitable NTO optimization tool parameter plan (Priority and Fall-off were 500 and 0.5,respectively) was lower (3.449 vs 3.655,P=0.000,Z=-5.534),the actual treatment time was not different (2.65 min vs 2.32 min,P=0.063,Z=0.832),and the PTV D_max was larger (132.1% vs 128.8%,P=0.002,Z=4.214).CI was larger (0.911 vs 0.879,P=0.151,Z=0.984).In summary,if the plan can be passed,when the NTO optimization tool parameter Distance from Target Border is set to 0.2 cm,Start Dose is set to 91% of the prescription dose,End Dose is set to 49.4% of the prescription dose,Fall-off and Priority are set to 0.5 and 500 respectively,the stereotactic radiotherapy plan for spinal metastases can achieve better target dose conformity,lower dose gradient index and appropriate treatment time.