Clinically relevant quality assurance for intensity modulated radiotherapy plans: Gamma maps and DVH-based evaluation

Purpose: To explore a novel patient-dose DVH-based method for pretreatment dose quality assurance tests. Methods: 20 IMRT plans for head-and-neck cancer patients were used. A comparison was performed between the planned dose distributions, the computed, and the reconstructed ones using the gamma-index (GI) method. The GI analysis was performed using both the 3%/3 mm and the 2%/2 mm criteria. Results: No significant DVH-deviation was observed. Considering the 3%/3 mm criteria the mean GI% <1 for the body and structures was significantly higher compared to 2%/2 mm criteria. Conclusions: Our results underline the importance of QA-methods based on DVH-metrics to predict the impact of delivered dose.