期刊论文详细信息
Radiation Oncology
The sensitivity of gamma-index method to the positioning errors of high-definition MLC in patient-specific VMAT QA for SBRT
Jong Min Park3  Sung-Joon Ye1  Jin Ho Kim2  Hak Jae Kim2  So-Yeon Park4  Jung-in Kim3 
[1] Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Seoul, Korea;Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea;Center for Convergence Research on Robotics, Advance Institutes of Convergence Technology, Suwon, Korea;Interdiciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea
关键词: High-definition multi-leaf collimator;    Dose-volumetric indicator;    Gamma-index method;    Stereotactic body radiation therapy;    Patient-specific quality assurance;   
Others  :  1132064
DOI  :  10.1186/1748-717X-9-167
 received in 2013-12-20, accepted in 2014-07-21,  发布年份 2014
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【 摘 要 】

Background

To investigate the sensitivity of various gamma criteria used in the gamma-index method for patient-specific volumetric modulated arc therapy (VMAT) quality assurance (QA) for stereotactic body radiation therapy (SBRT) using a flattening filter free (FFF) photon beam.

Methods

Three types of intentional misalignments were introduced to original high-definition multi-leaf collimator (HD-MLC) plans. The first type, referred to Class Out, involved the opening of each bank of leaves. The second type, Class In, involved the closing of each bank of leaves. The third type, Class Shift, involved the shifting of each bank of leaves towards the ground. Patient-specific QAs for the original and the modified plans were performed with MapCHECK2 and EBT2 films. The sensitivity of the gamma-index method using criteria of 1%/1 mm, 1.5%/1.5 mm, 1%/2 mm, 2%/1 mm and 2%/2 mm was investigated with absolute passing rates according to the magnitudes of MLCs misalignments. In addition, the changes in dose-volumetric indicators due to the magnitudes of MLC misalignments were investigated. The correlations between passing rates and the changes in dose-volumetric indicators were also investigated using Spearman’s rank correlation coefficient (γ).

Results

The criterion of 2%/1 mm was able to detect Class Out and Class In MLC misalignments of 0.5 mm and Class Shift misalignments of 1 mm. The widely adopted clinical criterion of 2%/2 mm was not able to detect 0.5 mm MLC errors of the Class Out or Class In types, and also unable to detect 3 mm Class Shift errors. No correlations were observed between dose-volumetric changes and gamma passing rates (γ < 0.8).

Conclusions

Gamma criterion of 2%/1 mm was found to be suitable as a tolerance level with passing rates of 90% and 80% for patient-specific VMAT QA for SBRT when using MapCHECK2 and EBT2 film, respectively.

【 授权许可】

   
2014 Kim et al.; licensee BioMed Central Ltd.

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