An Efficient Method for Improving the Dose-Volume-Based Optimization Plan Quality

Dose-volume (DV)-based objectives are widely used in most intensity-modulated radiation therapy treatment planning, because numerous DV endpoints have been utilized. In clinical practice, DV-based optimization (DVO) with uniform or random initial intensity distributions is utilized, but without considering the non-convexity of the DV objectives. To improve the quality of DVO radiotherapy plan and reduce the local minimum error generated by non-convexity of the DV objective, we proposed an efficient method (an organ-model-based optimization guiding DVO) to determine the initial intensity distributions for DVO. The new approach includes two steps. First, fluence map optimization, based on the organ model that adopts our proposed increasing objective function, to assure organ evaluation criteria Pareto surface, was performed. Second, DVO procedure was performed by using the initial intensity distributions determined in the first step. We demonstrated this technique in two kinds of clinical cases. DV histogram metrics were adopted as the criterion to evaluate the treatment plans. Compared with the conventional DVO plan with uniform initial intensity distributions, the improved DVO plan provided better protection of organ at risk (OAR); the planning target volume coverage was similar. Moreover, the improved DVO plan was better than the plan generated in the first step. The proposed method, with advantages in determining the initial intensity distributions, was highly efficient to improve DVO plans.