Comparison of different systems for quality assurance applied volumetric arc therapy (VMAT) plans in head and neck cancer

Purpose: To compare various dose verification systems used in Volumetric Modulated Arc Therapy (VMAT) in terms of their reliability and applicability with treatment planning system (TPS) on dosimetric aspects. Material and Methods: In this study, the accuracy of VMAT plans, which were prepared by using Eclipse (Varian Medical Systems) TPS, were compared with different (various) dose verification systems for a total of thirty one locally advanced head and neck cancer patiens before their treatment. The VMAT plans were checked with ArcCheck (Sun Nuclear) diode detectors, EPID (Varian Medical Systems) and EPIQA quality assurance (QA) systems using gamma analysis method. The QA plans for each patient were created by placing the gantry, collimator and table angles in the appropriate positions in the Eclips TPS for all QA systems. The plans for each QA systems were irradiated with TrueBeam. Dose maps were obtained with irradiation. Dose difference was 3%, whereas distance to agreement was 3 mm selected for comparison QA systems. Statistical analyzes were performed using SPSS Version 24 program Correlation analysis and Sample Paired T-test. Results: The average results of ArcCheck, EPID and EPIQA using gamma analysis method compared with TPS was observed as %98,41 (94,9-100) (±1,700), %99,70 (98,6-100) (±0,329), %96,78 (86,7-99,32) (±2,893) , respectively. According to gamma analysis results, two of the measurements made with ArcCheck and EPIQA did not pass acceptance limit (%95), but ArcCheck's measurement results too close to acceptance limit (%95). Besides this, all of the measurements made with EPID are above the 95% acceptance limit. The r values obtained by Correlation analysis were 0,506 for compared ArcCheck and EPID, 0,132 for compared EPID and EPIQA, 0,203 for compared ArcCheck and EPIQA. Conclusion: ArcCheck and EPID devices can be used interchangeably when comparing the measurement results of the qualitative reliability systems of the VMAT plans in the local advanced head and neck cancer with the Sample Paired T test and the Correlation test. Key Words: head and neck cancer, VMAT, quality assurance systems, gamma analysis