SU‐E‐E‐10: Statistical Process Control for VMAT Pre‐Treatment Verification QA Using ArcCHECK and Mobius3D

Abstract

Purpose:Process capability indices (PCI) are intended to provide single number assessment of ability to meet specification limits on quality characteristics of interest. It can be deduced from the multiple literature citations that PCI are both an effective and excellent means of measuring quality and performance, and have been widely used in the manufacturing industry. This work applied PCI to establish the control limits of the gamma analysis pass rate percentage for patient specific volumetric modulated arc therapy (VMAT) quality assurance (QA), and to evaluate the efficiency of the QA process by using the process capability performance measurement index (Cpm).Methods:335 QA plans were measured and evaluated with Mobius3D, a software designed to be an independent treatment plan evaluation tool, and ArcCHECK, a hardware/software product designed for measurement‐based patient‐specific plan QA analysis. The Γ‐(3%/3mm) criteria were used to evaluate the QA plans.Results:A statistical analysis of the Γ‐(3%/3mm) passing rates was performed. The Cpm calculated to evaluate QA the capabilities and suitability of the Mobius3D and ArcCHECK QA.The Cpm values of Mobius3D QA was 1.73 and ArcCHECK QA was 1.82 The average Γ‐(3%/3mm)pass was 96.2 +/−2.9 % for ArcCHECK and 95.3 +/−2.1 % for Mobius3D.Conclusion:Statistical process controls are useful to quantifiably demonstrate the QA process conformance to specifications. Systematic errors were greater with the ArcCHECK QA process than with the Mobius3D QA process. We speculate that this is due to the physical effort/manual intervention required to setup the ArcCHECK phantom for the measurements.Both the Mobius3D and ArcCHECK QA processes have proven to be acceptable because the values are higher than 1.0