Application of equivalent uniform dose based on organs-at-risk partition constraint in volumetric modulated arc therapy for rectal cancer(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2018年第1期
- Page:
- 36-40
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Application of equivalent uniform dose based on organs-at-risk partition constraint in volumetric modulated arc therapy for rectal cancer
- Author(s):
- ZUO Yuhao1; YANG Zhen2; ZHOU Jianliang1; LEI Mingjun2; CAO Ying2; YANG Xiaoyu2; TANG Du2; LIU Lidong1
- 1. College of Nuclear Science and Technology, University of South China, Hengyang 421000, China; 2. Department of Oncology, Xiangya Hospital, Central South University, Changsha 410008, China
- Keywords:
- ; Keywords: rectal cancer; partition constraint; equivalent uniform dose; volumetric modulated arc therapy; organs-at-risk
- PACS:
- R815；R735.3
- DOI:
- DOI:10.3969/j.issn.1005-202X.2018.01.008
- Abstract:
- Abstract: Objective To evaluate the dosimetric and biological advantages of equivalent uniform dose optimization based on organs-at-risk (OAR) partition constraint in volumetric modulated arc therapy (VMAT) for rectal cancer. Methods With dose-volume constraints, 10 VMAT plans for rectal cancer which were approved in clinic were selected (PHY plans). Based on the PHY plans, we performed the OAR partition according to the position relationships among the small intestine, the bladder and target areas, and carried out the equivalent uniform dose (EUD) optimization by giving different specific-tissues parameters (a value) which were different in sensitivity to hot spots, finally obtaining EUD plans. The greater a value was more sensitive to hot spots, and the dose of overlaps between target areas and OAR was relatively higher than that of other regions, with a higher probability of occurrence of hot spots, thus we selected a larger a value (a=10) to perform EUD optimization. The area where 9 mm expanded from the overlapping portions was intersected with the small intestine and the bladder had a low incidence of hot spots, therefore a value was at 8 and 5. As the rest of small intestine and bladder were away from high-dose area, we took a value of 6.7 and 2.3. The dosimetric and biological features of EUD plans and PHY plans were compared and SPSS 22 software was used to analyze the obtained data. Results The differences between PHY plan and EUD plan in PTV parameters were trivial. However, compared with PHY plans, EUD plans had reduced OAR dose parameters and normal tissue complication probability, with statistically significant differences (P<0.05). In EUD plan, the mean dose of the small intestine and the bladder decreased by 4.5 and 6.8 Gy,respectively; NTCP decreased 40.0% and 6.6%, respectively. Conclusion EUD optimization based on OAR partition constraint in VMAT for rectal cancer obviously decreases the OAR irradiation dose and normal tissue complication probability, without affecting PTV, which is significant to improve the quality of the plan.
Last Update: 2018-01-25