Design of a semi-spherical applicator for intraoperative radiotherapy with a linear accelerator and assessment of its dosemetric characteristics based on Monte Carlo simulation
10.3760/cma.j.issn.0254-5098.2020.11.010
- VernacularTitle:基于蒙特卡罗方法的脑转移瘤术中放疗施照器设计及剂量学评估
- Author:
Pan MA
1
;
Yongbao LI
;
Minghui LI
;
Chuanmeng NIU
;
Xin XIE
;
Min MA
;
Bo LIU
;
Fugen ZHOU
;
Jianrong DAI
Author Information
1. 国家癌症中心 国家肿瘤临床医学研究中心 中国医学科学院北京协和医学院肿瘤医院放疗科，北京 100021
- From:
Chinese Journal of Radiological Medicine and Protection
2020;40(11):868-872
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To design a semi-spherical applicator for delivery of semi-spherical dose distributions and assess its dosemetric characteristics.Methods:The applicator was designed in the following way. First, the scattering angle and dose rate of the electron beam having passed through a series of scattering foils of different thicknesses were calculated to determine the thickness of the scattering foil. And then, a series of location model was designed, and the variances of the mean electron energy on the surface of these models were calculated to determine the foil location. Finally, the relationship between the geometric characteristics of the layer and the surface dose on the applicator was established to design the modulator. Monte Carlo (MC) codes EGSnrc/BEAMnrc and EGS4/DOSXYZ were employed to model the head of the Mobetron, the location model, the layer, the semi-spherical applicator, and to calculate the dose distributions.Results:A semi-spherical applicator was designed for electron beam of energy 12 MeV, which consisted of a 2.5 cm diametre cylindrical collimator with 0.5 cm thick wall made of 0.3 cm thick steel and 0.2 cm thick water equivalent material (WEM), a 0.14 cm-thick foil made of tansgen, and a 2.5 cm diametre hollow semi-sphere containing a crescent modulator made of WEM. The dose rate was about 160 cGy/min, and the depth of the 50% isodose curve was 0.85 cm.Conclutions:We designed and performed a MC simulation of a semi-spherical applicator to deliver a semi-spherical dose distribution from a high energy electron beam.
