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Gamma Evaluation Combined with Isocenter Optimal Matching in Intensity Modulated Radiation Therapy Quality Assurance

Authors
 Jino Bak  ;  Jin Hwa Choi  ;  Suk Won Park  ;  Kwangwoo Park  ;  Sungho Park 
Citation
 JOURNAL OF THE KOREAN PHYSICAL SOCIETY, Vol.67(12) : 2131-2137, 2015 
Journal Title
 JOURNAL OF THE KOREAN PHYSICAL SOCIETY 
ISSN
 0374-4884 
Issue Date
2015
Keywords
Isocenter optimal matching (IOM) ; Gamma evaluation ; Dose distribution ; IMRT ; Patient-specific quality assurance (QA)
Abstract
Two-dimensional (2D) dose comparisons are widely performed by using a gamma evaluation with patient-specific intensity modulated radiation therapy quality assurance (IMRT QA) or dose delivery quality assurance (DQA). In this way, a pass/fail determination is made for a particular treatment plan. When gamma evaluation results are close to the failure criterion, the pass/fail decision may change applying a small shift to the center of the 2D dose distribution. In this study, we quantitatively evaluated the meaning of such a small relative shift in a 2D dose distribution comparison. In addition, we propose the use of a small shift for a pass/fail criterion in gamma analysis, where the concept of isocenter optimal matching (IOM) is applied to IMRT QA of 20 patients. Gamma evaluations were performed to compare two dose distributions, one with and the other without IOM. In-house software was developed in C++ in order to find IOM values including both translational and rotational shifts. Upon gamma evaluation failure, further investigation was initiated using IOM. In this way, three groups were categorized: group 1 for ‘pass’ on gamma evaluation, group 21 for ‘fail’ on the gamma evaluation and ‘pass’ on the gamma the evaluation with IOM, and group 22 for ‘fail’ on the both gamma evaluations and the IOM calculation. IOM results revealed that some failures could be considered as a ‘pass’. In group 21, 88.98% (fail) of the averaged gamma pass rate changed to 90.45% (pass) when IOM was applied. On average, a ratio of γ ≥ 1 was reduced by 11.06% in 20 patients. We propose that gamma evaluations that do not pass with a rate of 85% to 90% may be augmented with IOM to reveal a potential pass result.
Full Text
https://link.springer.com/article/10.3938/jkps.67.2131
DOI
2015
Appears in Collections:
1. College of Medicine (의과대학) > Dept. of Radiation Oncology (방사선종양학교실) > 1. Journal Papers
Yonsei Authors
Park, Kwang Woo(박광우) ORCID logo https://orcid.org/0000-0002-9843-7985
URI
https://ir.ymlib.yonsei.ac.kr/handle/22282913/157127
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