Room: Davidson Ballroom A
Purpose: High dose-rate brachytherapy (HDRBT) is widely used for gynecological cancer treatment. Although commercial treatment planning systems (TPSs) have inverse optimization modules, it takes several iterations to adjust planning objectives to achieve a satisfactory plan. Interactive plan-modification modules enable modifying the plan and visualizing results in real time, but they update plans based on simple geometrical or heuristic algorithms, which cannot ensure resulting plan optimality. This project develops an interactive plan optimization module for HDRBT of gynecological cancer. By efficiently solving an optimization problem in real time, it allows a user to visualize plan and interactively modify it to improve quality.
Methods: We formulate an optimization problem with an objective function containing weighted sum of doses to normal organs subject to user-specified target coverage. A user interface is developed that allows a user to adjust organ weights using scroll bars. Up on release a mouse click, the optimization problem is solved in seconds with a highly efficient alternating-direction method of multipliers and a warm start optimization strategy. Resulting clinically relevant D2cc of organs are displayed immediately. This allows a user intuitively adjust plan towards satisfactory quality. We tested effectiveness of our development in cervix cancer cases treated with a tandem-and-ovoid applicator.
Results: It took maximally 3 second to solve the optimization problem each time. With interactive optimization capability, a satisfactory plan can be obtained in <1 min. In our clinic, although the time for plan adjustment was typically <5min with simple interactive plan modification tools in TPS, the resulting plans do not ensure optimality. Our plans achieved on average 5% lower D2cc than clinical plans, while maintaining target coverage.
Conclusion: The interactive optimization tool is effective in terms of helping a planner to generate a plan with improved efficiency and plan quality.