Room: AAPM ePoster Library
The purpose of this study is to introduce a novel method to determine optimal arc parameters in VMAT such as arc length, angle of avoidance and number of arcs required for a given plan
Our approach is based on the following assertion: If a Control point’s dose contribution from an optimal angle is removed from an optimized VMAT plan, it will result in a larger increase in the OFV. Likewise, if a Control point’s dose contribution from a non-optimal or sub-optimal angle is removed from the optimized VMAT plan, it will result in a lesser increase in the OFV . By using this assertion, we have optimized the aforementioned arc parameters and performed VMAT optimization. Subsequently, we have compared the results with a conventional VMAT plan with full arcs (single/dual arcs). We used Pinnacle3 TPS to create clinical VMAT plans for three anatomical sites (Prostate, Lung and Abdomen). All plans were created using Varian True beam machine with single/dual arc technique with 6 MV photon beams.
We have compared both set of plans (VMATConventional and VMATArcOptimized) in terms of DVH statistics, Delivery time, Number of control points and Low dose volume (Volume covered by 5Gy). Compared to VMATConventional plans, VMATArcOptimized plans resulted in significantly lesser low dose volume (on the average, 6.15%) with comparable target dose coverage and homogeneity. In addition, total number of control points are reduced by 16.8% and delivery time is reduced by 29.7 % in VMATArcOptimized as compared to VMATConventional Plans. Compared to VMATConventional plans, VMATArcOptimized plans resulted in significantly lower OAR mean doses (on the average 16.7 %)
It is evident from the study that the proposed method can be effectively applied to determine the optimal arc parameters for a given VMAT plan to improve the delivery efficiency