A comprehensive site-specific analysis of patient-specific quality assurance based on dose volume histogram of RapidArc treatment delivery.

Background: The current study aims to evaluate the use of dose-volume histogram (DVH) metrics as part of a comprehensive pre-treatment quality assurance (PSQA) protocol for RapidArc treatment delivery.

Materials and methods: A total of ninety patients were included in this study, with the patient population divided into four groups: Brain (n = 15), Head and Neck (H & N) (n = 30), Thorax (n = 15), and Pelvis (n = 30) RapidArc plans. The delivered dose was assessed using the Octavius 4D 1500 detector array and the Verisoft DVH application, focusing on DVH-related errors pertaining to targets and organ-at-risk (OARs). Additionally, three-dimensional local and global gamma passing rates were analyzed in the axial, coronal, and sagittal planes using various gamma criteria, including 3 mm/3%, 3 mm/2%, 2 mm/3%, and 2 mm/2%.

Results: All treatment plans met the action level requirement, achieving a gamma acceptance rate exceeding 95% with a 3%/3 mm criterion. Among the anatomical planes, the transverse plane consistently exhibited the highest passing rates for various global gamma criteria across all treatment sites. Local gamma analysis revealed that the coronal plane had the highest passing rates for thorax and pelvis sites compared to other planes. DVH analysis indicated that doses to target volumes remained within specified tolerances for all cases. The most significant OAR dose discrepancies were observed in the H&N region.

Conclusion: Integrating DVH metrics into the RapidArc PSQA protocol can yield clinically significant results closely aligned with the gamma index. It was observed that a single action-level approach cannot be universally applied to DVH metrics across different anatomical sites.