Premium
SU‐F‐P‐63: Individual Volume Based 3D Gamma Indices for Pretreatment VMAT QA
Author(s) -
Jin X,
Yi J,
Xie C
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4955771
Subject(s) - nuclear medicine , dose volume histogram , prostate cancer , volume (thermodynamics) , mathematics , nasopharyngeal cancer , radiation therapy , medicine , radiation treatment planning , cancer , radiology , nasopharyngeal carcinoma , physics , quantum mechanics
Purpose: To investigate the feasibility of individual volume based 3D gamma indices for pretreatment volumetric modulated arc therapy (VMAT) QA. Methods: Both model‐ and measurement‐based VMAT QA for one‐ and two‐arc VMAT plans were performed with COMPASS system. Percentage dosimetric errors (%DE) of dose‐volume histogram (DVH) metrics between TPS and QA reconstructed dose distribution, percentage gamma passing rate (%GP) for individual volume and global gamma indices, as well as the statistical correlations between %GP and %DE were investigated. The sensitivities of different %GP were also investigated. Results: The %DE of model‐based QA for most DVH metrics of VMAT plans were within 3%. There were 9, 12, and 9 out of 15 metrics %DE, and only 2 out of 15 %DE metrics were correlated with individual volume %GP and global %GP of nasopharyngeal cancer (NPC) with 2%/2 mm, 3%/3 mm and 4%/4 mm criteria, respectively. For prostate cancer, there were 18, 16 and 13 out of 23 %DE metrics, and 19, 12 and 1 out 23 of %DE metrics were correlated with individual volume %GP and global %GP with 2%/2mm, 3%/3mm and 4%/4mm criteria, respectively. The area under curves (AUC) of individual volume %GP were higher than those of global %GP for NPC patients, but with a mixed results for prostate cancer patients. Conclusion: Individual volume based %GP were strongly correlated with DVH metrics %DE compared with global %GP for both one‐ and two‐arc VMAT plans. Sensitivity analysis indicated that individual volume gamma indices were feasible for VMAT QA.