Validation of a 3D Pretreatment Quality Assurance Tool for Volumetric Modulated Arc Therapy (VMAT)

Abstract

Implementation of a pretreatment quality assurance (QA) system needs a strong validation process and a good comprehension of the tool. The aim of this study is to validate COMPASS (IBA Dosimetry, Germany) as our 3D pre- treatment QA tool for system of Pinnacle as treatment planning system and an ELEKTA synergy linear accelerator. Validation of the systems was performed with static and dynamic plans on AAPM TG-119 phantom and 10 real VMAT plans for prostate and head and neck. Comparison between point dose from TPS and COMPASS was performed to evaluate the confidence limit in high dose region (98.5% and 98.6%) and low dose region (94.1% and 95.2%) for COMPASS computed and reconstructed dose respectively. For planar dose the confidence limit was respectively 95.37% and 96.35% for COMPASS computed and reconstructed dose. Clinical validation was evaluated by comparing dose-volume parameters for real VMAT plans with TPS values (mean differences were below of 1% for the target). The comparison between 2D dose distribution from TPS and dose extracted from COMPASS computed and reconstructed for real VMAT plans were also performed (mean global gamma passing rate better than 94% and 98% for the 2%/2mm and 3%/3mm criteria). The 3D dose distribution comparison between TPS and COMPASS was also performed with good gamma score for global and local analysis. COMPASS was successfully evaluated as our 3D pretreatment system.