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Feasibility and Sensitivity of Individual Volume Based 3D Gamma Indices for Composite IMRT QA
X Jin*, C Han , C Xie , the 1st Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang
Presentations
SU-I-GPD-T-291 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: Per-beam based intensity-modulated radiation therapy (IMRT) quality assurance (QA) had been questioned, and dose-volume histogram (DVH) metrics based QA have been developed and tested recently. However, for DVH based IMRT QA, previous simple passing rate is no longer applicable. The purpose of this study is to investigate the feasibility and sensitivity of individual volume based 3D gamma indices for composite DVH based IMRT QA.
Methods: Composite IMRT QA for 15 cervical cancer patients were performed with ArcCheck. Percentage dosimetric errors (%DE) of DVH metrics ( includes target volumes and organ at risks) between treatment planning system and QA reconstructed dose distribution, percentage gamma passing rate (%GP) for individual volumes and global gamma indices with different criteria (2%/2mm, 3%/3mm,4%/4mm) were evaluated, as well as their correlations. Receiver operating characteristic (ROC) curves were applied to study the sensitivities of global and individual volume gamma indices.
Results: Most of %DE of the DVH metrics were within 3%. The global %GP for 2%/2mm, 3%/3mm,4%/4mm were 87.78%±3.06%, 96.33%±1.57%, 99.03%±0.57%, respectively. For criteria of 2%/2mm, 3%/3mm,4%/4mm, individual volume %GP were correlated with 19, 17, and 13 out of 23%DE metrics, and global %GP were correlated with 10, 8, and 2 out 23 of %DE metrics, respectively. Individual volume based %GP had a higher percent of correlation with individual DVH metrics %DE compared with global %GP in composite IMRT QA. The area under curves (AUC) of individual volume %GP were higher than those of global %GP.
Conclusion: DVH metrics based IMRT QA were time consuming and inefficient. Individual volume based 3D gamma indices were feasible and sensitive for composite IMRT QA.
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