(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To develop a mixed integer linear programming (MILP) model for arc arrangement of noncoplanar VMAT treatment planning.
Methods: A MILP model is developed for arc arrangement of noncoplanar VMAT planning. The MILP model consists of the objective function and the constraints on the doses of target volume, critical organs, and normal tissue. In addition to the dose constraints, the specific constraints are included to account for the speed limits of gantry rotation and leaf motion, dose rate, etc. To validate the MILP model, one clinical case with tumor at right-anterior part of liver was investigated. Both noncoplanar and coplanar VMAT plans were made. The couch angle and arc range of noncoplanar VMAT plan was determined by MILP model, while the arc range of coplanar VMAT plan was set by experienced planner. The dosimetrical quality of both plans is evaluated by dose-volume histogram and dose distribution.
Results: Two partial arcs (arc 1: couch angle 320º and gantry angle [180º - 20º] clockwise; arc 2: couch angle 20º and gantry angle [180º - 20º] clockwise) of the noncoplanar VMAT plan were determined by the MILP model. Comparing to the dual arc coplanar VMAT plan with gantry angles between [180º - 20º] chosen by experienced human planner, the PTV dose coverage is comparable while the doses to most critical organs are reduced evidently.
Conclusion: Due to the nature of MILP, arc arrangement of noncoplanar VMAT plan converges quickly and the resulting solution is global optimum. The proposed MILP model provides an automated and effective way in determining the optimal arc arrangement of noncoplanar VMAT plan.
Funding Support, Disclosures, and Conflict of Interest: This research is funded by Varian research grant
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