Effect of field size on EPID verification of whole-brain radiotherapy plan(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2020年第6期
- Page:
- 661-665
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Effect of field size on EPID verification of whole-brain radiotherapy plan
- Author(s):
- ZHANG Jin1; NIE Xin2; XIONG Yi3
- 1. Department of Pharmacy, Zhongnan Hospital of Wuhan University, Wuhan 430071, China 2. Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China 3. School of Physics and Technology, Wuhan University, Wuhan 430072, China
- Keywords:
- Keywords: electronic portal imaging device intensity-modulated radiotherapy radiation field whole brain plan verification
- PACS:
- R312；R815
- DOI:
- DOI:10.3969/j.issn.1005-202X.2020.06.001
- Abstract:
- Abstract: Objective To verify whole-brain radiotherapy plan by electronic portal imaging device (EPID) using γ test for discussing the effects of plan design on test results, thereby analyzing how to optimize whole-brain radiotherapy plans and speculating the limitations of EPID in dose verification. Methods Sixty-seven patients scheduling for whole-brain radiotherapy were selected and their radiotherapy plans were verified by EPID on the accelerator. For volumetric modulated arc therapy (VMAT) plans, the relationship between X-direction field size and γ (3 mm/3%) passing rate was statistically analyzed. For intensity-modulated radiotherapy (IMRT) plans, the differences in γ (3 mm/3%) passing rate between whole-field and split-field plans were analyzed. Results The result of VMAT plan verification showed that the γ (3 mm/3%) passing rates of plans with X-direction field size less than 15 cm were generally superior to the ones with their X-direction field size greater than or equal to 15 cm, and the results of t-test by SPSS software also verified that the results had statistical significance (t=-3.828, P<0.05). The result of IMRT plan verification showed that the radiation fields with X-direction greater than or equal to 15 cm contained two sub-fields. The γ (3 mm/3%) passing rate was lower in their overlapping areas, while splitting these fields could gain a much better results for the elimination of overlapping areas. Conclusion For whole-brain VMAT plans, controlling the X-direction field size within 15 cm can improve the adjusting ability of multi-leaf collimators, thus improving γ (3 mm/3%) passing rate of EPID verification. Meanwhile, the deviation of the response of EPID to low dose area will lead to a lower γ (3 mm/3%) passing rate at the overlapping areas of two sub-fields inside the radiation field of whole-brain IMRT plans, but using split-field verification can significantly eliminate the effect.
Last Update: 2020-07-03