TH-D-AUD B-02: A Technique For Creating VMAT Plans Using Direct Machine Parameter Optimization

Abstract

Purpose: The objective of this study was to develop a technique for single rotation volume modulated arc therapy (VMAT) treatment plans using the current clinical version of the Pinnacle Treatment Planning system. The goal was to create treatment plans using only tools currently available in Pinnacle. Method and Materials:Treatment planning for VMAT was performed using the Direct Machine Parameter Optimization (DMPO) algorithm. With DMPO, inverse planning is performed by optimizing MLC leaf positions and segment weights. The treatment delivery was modeled and optimized as 51 equally spaced fixed beams. This beam geometry was selected to generate comparable plans to helical tomotherapy. Upon completion of optimization, the MLC delivery files were exported and converted into a single arc. Fixed‐gantry IMRT plans were also created for comparison by analyzing dose statistics, volume histograms, and differences. Calculated doses and MLC controller files were extracted from Pinnacle and imported into MATLAB for analysis. Gamma analyses were performed between the fixed‐gantry and VMAT plans. In addition, the modulation factor was calculated for the VMAT plans. Results: A total of 11 treatment plans were created for VMAT and fixed‐gantry IMRT. In all cases, the DMPO algorithm was able to optimize a plan resulting in one beam aperture. For prostate and HN and 2.) The VMAT plans have dose distributions similar to fixed‐gantry IMRT.