剂量限制辅助结构模板优化鼻咽癌调强计划应用研究

Application study of dose-limiting structure template on intensity-modulated radiation therapy treatment planning optimization

目的剂量限制辅助结构(dose limit structure,DLS)是放疗调强计划设计中最常用的工具,而目前临床上生成DLS的方法效率低且缺乏统一性。本研究采用软件程序化编译自动生成DLS,同时探讨DLS统一模板对计划结果的影响并扩展其临床应用。方法按优化的需求将DLS分为靶区(plan target volume,PTV)的外环和内环、靶区与危及器官(organ at risk,OAR)重叠区和特定的DLS 4种。对10例已优化好的鼻咽癌计划(Old-plan)采用MIM软件(V6.5)工作流模板自动生成DLS,并由原计划设计者依据DLS重新优化生成新计划(DLS-plan),比较两组计划靶区及OAR的剂量变化。结果工作流模板自动生成20~24个DLS平均耗时3.4min。在两组计划中,所有靶区(PGTVNX、PCTV-ND、PCTV1和PCTV2)的均匀指数(HI)值、PGTV-NX和PCTV1的95%处方剂量体积(V95)值、PCTV1的平均剂量(Dmean)值,变化差异均有统计学意义,均P<0.05。同时位置关系与靶区有重叠的OAR剂量分布均有改善,最大剂量(Dmax)值(脑干)、Dmean值(脑干、右侧视神经、双侧腮腺、脊髓及气管)和V30值(左侧腮腺),变化差异均有统计学意义,均P<0.05。结论模板化的DLS有利于将优化经验固化并提高计划质量。MIM软件所提供的工作流编译功能使DLS的生成自动化,简化了操作流程,便于临床应用。

OBJECTIVE The dose limit structure(DLS)is the most commonly used tool in intensity-modulated radiation therapy(IMRT)planning optimization.At present,the method of generating DLS in clinic is inefficient and lacks uniformity.In this study,to study the DLS template impact on the results of planning optimization,and to extend its clinical application by software programmatic compilation and automated generation.METHODS According to the optimization requirements,the DLS was divided into four types:PTV-outer ring,PTV-inner ring,the overlap volume between target and organ at risk(OAR),and specific DLS.The DLS was automatically generated from 10 optimized NPC plans(Old-plan)with the MIM software(V6.5)workflow template,and re-optimized by original planning designers to generate new plan(DLS-plan)based on DLS.Dose variations in PTV and OAR between two groups were compared.RESULTS For a workflow template,automatically generating 20 to 24 DLS took only 3.4 minutes on average.The HI of all PTV,V95 of PGTV-NX and PCTV1,Dmean of PCTV1 were changed with statistical differences(P<0.05).The dose distribution in the overlap volume between target and OAR was significantly improved.Dmax of brainstem,Dmean of brainstem,optic nerve(R),parotid glands,spinal cord and trachea,V30 of parotid gland(L)were changed with statistical differences(P<0.05).CONCLUSIONS To templated DLS facilitates optimization experience and improves planning quality.The workflow compilation function provided by MIM software automatically generates DLS and simplifiys operating procedures for further clinical application.