A novel audit methodology to improve detection of planning and delivery errors in passive motion management

Background and purpose: End-to-end dosimetry audits, including respiratory motion, typically compare film measurements acquired in a moving frame directly to planned dose distributions that do not resolve the applied motion. Inherent motion-induced dose differences cannot be distinguished from error-induced differences in this analysis. An alternate comparison approach is proposed utilising both motion-coupled and decoupled film measurements to overcome the motion-induced differences, and improve error detection. Materials and methods: ) was used to calculate sensitivity/specificity using the standard and proposed (test) comparison approaches. Results: ≥ 5% (range: -21.0% to + 3.0%). 3/25 combinations in the standard arm had sensitivity and specificity ≥ 0.5, versus 9/25 in the test arm. Standard analysis performed optimally using 5%/3mm criteria (sensitivity = 1.0, specificity = 0.62). The test arm had equal sensitivity with improved specificity (0.75) using 4%/2mm criteria. Conclusions: Film measurements acquired in a moving frame are over-sensitive with low specificity. Eliminating the impact of motion using the proposed measurement/analysis approach enables more stringent gamma criteria (4%/2mm versus 5%/3mm) for better classification accuracy.