Investigation of a Monte Carlo model of scanning nozzle(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2019年第9期
- Page:
- 1001-1007
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Investigation of a Monte Carlo model of scanning nozzle
- Author(s):
- WANG Jinlong1; QU Weiwei2; XIE Shuqing1; WANG Hongkai3; YUAN Xiaogang1
- 1. Proton Technology Department, Guangzhou Concord Cancer Center, Guangzhou 510555, China; 2. School of Radiation Medicine and Protection, Medical College of Soochow University, Suzhou 215123, China; 3. Nuclear and Radiation Safety Center, Ministry of Ecology and Environment, Beijing 102400, China
- Keywords:
- ; Keywords: scanning nozzle; proton therapy; Monte Carlo simulation
- PACS:
- R312；R811.1
- DOI:
- DOI:10.3969/j.issn.1005-202X.2019.09.002
- Abstract:
- Abstract: Objective To estimate the effects of scanning nozzle in proton therapy on beam quality. Methods A Monte Carlo model of scanning nozzle was established to investigate the variation of depth dose curve, calculate the effect of range shifter on the cross section of beam spot and analyze the deflection of single proton beam caused by scanning magnet field. Results With the increase of energy, the range of proton in water was increased, and meanwhile scattering was more serious. Finally, the Bragg peak became wider and the tail became fatter. Compared with the direct incident into water phantom, the range of proton passing through the scanning nozzle in water was shortened by about 0.6 cm, but the Bragg peak shape remained basically unchanged. The range shifter of 4 cm thick polyethylene was placed at 0, 10, 20, 30, 40 and 50 cm away from the water phantom surface for independent calculation, and it was found that the farther the distance from the water phantom was, the greater the proton scattering was. Therefore, the range shifter should be as close as possible to the patient during treatment. The beam spot deviated from beam center due to the magnetic field loaded by scanning magnet. With the longitudinal magnetic field Bx = 0.1 T and transverse magnetic field By=0.3 T, 180 MeV proton beam had a deviation of 2.693 cm in Y direction and 8.427 cm in -X direction. When the beam was deflected, the cross section of range shifter was required to be wide enough to satisfy the need of wide scan field. Conclusion The Monte Carlo model of scanning nozzle is helpful for understanding proton therapy as an emerging radiotherapy method and the beam characteristics of scanning therapy and providing good references in commissioning and quality assurance.
Last Update: 2019-09-23