Out-of-field dose distributions of different beams from Varian Edge accelerator and protection effects of lead protective equipments(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2020年第8期
- Page:
- 982-988
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Out-of-field dose distributions of different beams from Varian Edge accelerator and protection effects of lead protective equipments
- Author(s):
- WANG Haiyang; PI Yifei; GUO Yuexin
- Department of Radiation Oncology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
- Keywords:
- Keywords: out-of-field dose distribution lead protective equipment secondary cancer radiotherapy planning
- PACS:
- R815
- DOI:
- DOI:10.3969/j.issn.1005-202X.2020.08.008
- Abstract:
- Abstract: Objective To study the out-of-field dose distributions of different beams from Varian Edge accelerator under different working conditions and to investigate the protection effects of lead protective equipments. Methods When different energy levels, flattening filter-free (FFF) or flattening filter (FF) mode, and different protective equipments were adopted, the variations of the dose distributions at different distances from the edge of the beam field and at different depths of measurement were determined by experimental measurements. Results The out-of-field dose distributions were approximately exponentially decreasing with increasing distance from the edge of the beam field (5-40 cm). Within 20 cm from the edge of the beam field, the irradiation dose of low-energy beams (6 MV, 6 MV FFF) was lower than that of high-energy beams (10 MV, 10 MV FFF), and the irradiation dose was decreased with the increase of the depth of measurement (1-2 cm). FFF mode had more obvious effects on reducing the out-of-field dose distributions as compared with FF mode. Under the same energy condition, the protective effect of lead protective equipments was independent on FF or FFF mode. The protection against high-energy beams was better than that against low-energy beams, and the protective effect was decreased rapidly with the increase of the depth of measurement. When the depth of measurement was 1 cm, the protective effect was the strongest for the condition of 10 MV FFF beams and 5-30 cm from the edge of the beam field, and the reduction of out-of-field doses was larger than 50%. When the depth of measurement was 2 cm, the protective effect was the worst for the condition of 6 MV FFF beams and 5-30 cm from the edge of the beam field, and only a reduction of 10% was achieved. Conclusion Under the premise of achieving clinical goals, if no lead protective equipments were applied during the treatment, it is recommended to adopt low-energy FFF beams. If lead protective equipments were used for protection, high-energy FFF beams can be adopted, and at that time, the protective effect of lead protective equipments is the best, and the shallow organs out of the field are irradiated by the lowest dose, which can greatly reduce the probability of secondary cancer.
Last Update: 2020-08-27