An inverse dose optimization algorithm for three-dimensional brachytherapy / 中华放射肿瘤学杂志

ABSTRACT

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(D 100%, V 150%) and organs at risk(D 0.1cm 3, D 1.0cm 3, D 2.0cm 3) 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 D 100% of the GBPO plan was significantly higher ( P<0.01), and the V 150% 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.