Evaluation of Patient-Specific Quality Assurance for RapidArc Treatment Delivery Using Dose Volume Histogram

This study aims to evaluate the application of dose volume histogram (DVH) metrics within the patient-specific quality assurance (PSQA) protocol in various sites for RapidArc treatment delivery. Forty patients were included in this study, of which twenty each Head and Neck (H&N) and Pelvis Rapid Arc plans were evaluated. Octavius 4D 1500 detector array with vented parallel plate ion chambers was used for this study, which reconstruct the pre-treatment measured doses into threedimensional (3D) during pre-treatment quality assurance. The verisoft DVH application was utilized to estimate the dose administered to the patient's volume, explicitly focusing on the errors associated in the DVH. The measured data were compared with the treatment planning system created verification plan. Three-dimensional local and global gamma were evaluated using different gamma criteria of 3 mm/3%, 3 mm/2%, 2 mm/3% and 2 mm/2%, respectively. In addition, the agreement score was analysed for axial, coronal, and sagittal planes in addition to the volumetric analysis. All plans meet the action level requirement of > 95% with 3%/3 mm gamma acceptance criteria. In addition, the DVH demonstrated that the doses administered to the target volumes and organs at risk remained within the specified dose tolerances for all cases. The DVH analysis will be applied to identify the instances where patient dose errors surpass the predetermined established action threshold. The gamma index did not initially identify these and may have utility in determining the reason for failed plans. Further, it enables identifying and managing dose errors associated with the patient's anatomy. Finally, this study has showcased the incorporation of DVH metrics into RapidArc PSQA protocol may deliver clinically meaningful outcomes in close proximity to the gamma index.