三维后装治疗中一种逆向剂量优化算法

目的 探讨三维后装治疗计划中一种逆向剂量优化算法(GBPO)的实现方法和结果。方法 GBPO使用标准的二次目标函数,优化代码基于LBFGS算法。回顾性选择了 7例使用不同施源器治疗的宫颈癌患者和 15例使用了三管施源器治疗的宫颈癌患者,先用等剂量线定性评估GBPO计划的质量,然后统计剂量体积直方图(DVH)参数(CTV D100%、V150%,危及器 官D0.1cm³、D1.0cm³、D2.0cm³),评估GBPO计划、IPSA计划和Graphic计划之间的差异。结果 对于使用不同施源器的 7例患者,GBPO都可以优化出适形的剂量分布,GBPO计划、IPSA计划和Graphic计划之间靶区和危及器官的DVH参数相近。对于使用了三管施源器的 15例患者,GBPO计划和IPSA计划之间DVH参数也相近,GBPO计划和Graphic计划之间危及器官DVH参数也相近,但是GBPO计划CTV的D100%高于Graphic计划(P<0.01),V150%低于Graphic计划(P<0.01)。结论 采用逆向剂量优化算法GBPO制订的计划在靶区覆盖和危及器官保护方面与IPSA计划相似,GBPO可集成在三维后装治疗计划系统中。

An inverse dose optimization algorithm for three-dimensional brachytherapy

Objective To explore an implementation method and results of an inverse dose optimization algorithm (gradient-based planning optimization, GBPO) in three-dimensional brachytherapy. Methods A standard quadratic objective function was used in the GBPO. The optimization code of GBPO was performed based on LBFGS (Limited memory Broyden Fletcher Goldberg Shanno). Seven cervical cancer patients using different applicators and 15 cervical cancer patients using the Fletcher applicator (Nucletron part#189.730) were retrospectively analyzed. The plan quality of GBPO was firstly assessed by isodose lines, then dose-volume histogram (DVH) parameters of CTV(D100%,V150%) and organs at risk(D0.1cm³,D1.0cm³,D2.0cm³) were used to evaluate the difference among the GBPO, IPSA and Graphic plans. Results For the 7 patients using different applicators, GBPO could optimize the conformal dose distribution, and the DVH parameters of the target and organs at risk were basically the same among the GBPO, IPSA and Graphic plans. For 15 patients using the Fletcher applicator, the difference in DVH parameters between the GBPO and IPSA plans was not statistically significant. There was no remarkable difference in the DVH parameters between the GBPO and Graphic plans, but the D100% of the GBPO plan was significantly higher (P<0.01), and the V150% was significantly lower (P<0.01) than that of the Graphic plan. Conclusions The quality of the GBPO plan is similar to that of the IPSA plan in terms of target coverage and organ protection. The inverse dose optimization algorithm GBPO can be integrated into a three-dimensional brachytherapy treatment planning system.