Effect of overlapping areas on craniospinal irradiation plans(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2018年第2期
- Page:
- 131-134
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Effect of overlapping areas on craniospinal irradiation plans
- Author(s):
- JU Mengyang1; SHI Yujing1; TIAN Tian2; SUN Xinchen2
- 1. Department of Medicine in Specific Environments, Nanjing Medical University, Nanjing 210009, China; 2. Department of Radiation Oncology, the First Affiliated Hospital of Nanjing Medical University, Nanjing 210009, China
- Keywords:
- ; craniospinal irradiation; overlapping area; setup error; conformity index; homogeneity index
- PACS:
- R739.4；R815.6
- DOI:
- DOI:10.3969/j.issn.1005-202X.2018.02.002
- Abstract:
- Objective To set different sizes of overlapping areas and setup errors during the design of craniospinal irradiation (CSI) plan and analyze the effects of overlapping lengths on CSI plans. Methods Eight patients treated with CSI were retrospectively collected. Six overlapping lengths, namely 1, 2, 4, 6, 8 and 10 cm, were set to design CSI plans, and the qualities and implementations of plans with different overlapping lengths were compared. Based on the above six lengths, we simulated different setup errors in head-feet direction, and then conducted the plan optimization. The effects of overlapping lengths and setup errors on plans were compared. Results A total of 272 treatment plans were designed for 8 patients. When the overlapping lengths were 1, 2, 4, 6, 8 and 10 cm, all plans were able to meet prescribed requirements (95%-107% PTV was covered). However, the prescribed dose coverage rate was 95.2%±1.0% in plans with the overlapping length of 1 cm, smaller than the other plans (P=0.000). With the overlapping lengths increasing from 2 cm to 10 cm, the conformity index increased, while the homogeneity index decreased (P=0.03). When the setup errors were ±0.5 cm or larger, the dose distribution in overlapping areas was obviously uneven. Conclusion The overlapping of irradiation field which in a proper range avoids the movement of irradiation field during CSI, reducing the system error. Considering the six overlapping lengths above, when the overlapping length raises from 4 cm to 10 cm, the plans meet the plan requirements. Moreover, the setup errors smaller than 0.5 cm scarcely affect the plan.
Last Update: 2018-01-29