Abstract Objective To investigate the application of the Monte Carlo dose calculation of output factors for electron beams in radiotherapy. Methods The code EGS4/MCTP was used to simulate the head of a medical linear accelerator (Varian 23EX) to calculate the output factors for 6 MeV,9 MeV and 18 MeV electron beams. The source-to-surface distance used was 100 cm. The field sizes ranged from 2 cm×2 cm to 25 cm×25 cm. The calculated output factors agreed with the corresponding measured factors which were measured by the IBA Phantom system to within 2%. Then, the output factors of direct articles and indirect articles which were under different energy and various cone-insert combinations were calculated by the code EGS4/MCTP. Results The calculated output factors agreement with the measurements is found to be mostly under the 1% level. The variation of output factors depends on the characteristics of the beams and themodifications that the various cone-insert combinations introduce to these characteristics. Conclusions Monte Carlo dose calculations for electron beams in homogeneous water phantoms have been demonstrated to be accurate under the 1% level in comparison with measurements. The output factors were influenced by energy and cone-insert combinations in complex ways.
Chi Zifeng*,Liu Dan,Zhang Yong et al. Analysis of electron beam output factors by Monte Carlo method[J]. Chinese Journal of Radiation Oncology, 2014, 23(3): 265-268.
Chi Zifeng*,Liu Dan,Zhang Yong et al. Analysis of electron beam output factors by Monte Carlo method[J]. Chinese Journal of Radiation Oncology, 2014, 23(3): 265-268.
[1] Hogstrom KR, Mills MD, Almond PR. Electron beam dose calculations[J]. Phys Med Biol,1981,26:445-459. [2] Nahum AE. The computation of dose distributions in electron beam radiotherapy[D]. Umea:University of Umea,1985. [3] Cygler J, Battista JJ, Scrimger JW, et, al. Electron dose distributions in experimental phantoms:a comparison with 2D pencil beam calculations[J]. Phys Med Biol,1987,32:1073-1086. [4] Mah E, Antolak J, Scrimger JW, et al. Experimental evaluation of a 2D and 3D electron pencil beam algorithm[J]. Phys Med Biol,1989,34:1179-1194. [5] AAPM Task Group 21. Radiation therapy committee:a protocol for the determination of absorbed dose from high-energy photon and electron beams[J]. Med Phys,1983,10:741-71. [6] AAPM TG-25. Clinical electron beam dosimetry:report of AAPM Radiation Therapy Committee Task Group No.25[J]. Med Phys,1991,18:73-109. [7] AAPM Task Group 39. Radiation therapy committee:the calibration and use of plane-parallel ionization chambers for dosimetry of electron beams:an extension of the 1983 AAPM protocol report of the AAPM Radiation Therapy Committee[J]. Med Phys,1994,21:1251-1260. [8] Ma CM, Rogers DWO. Beam characterization:a multiple source model. Technical report PIRS 509d, National Research Council of Canada. Ottawa:NRCC,1995. [9] Ma CM, Faddegon BA, Rogers DWO, et al. Accurate characterization of Monte Carlo calculated electron beams for radiotherapy[J].Med Phys,1997,24:401-416. [10] 单国平,严英师.电子线不规则射野的输出因子研究[J].中华放射医学与防护杂志,2004,24:163-165. [11] 陈英海,杨月琴,邓涛,等.Varian 2300 C/D直线加速器高能电子线铅挡野输出因子的测定与分析[J].中国医学物理学杂志,2001,18:14-15. [12] 张颖,陶建民,胡杰,等.高能医用电子线输出因子的剂量学特性[J].现代医学,2010,38:458-461. [13] 沈国辉,张书旭,吴少焜,等.电子线输出剂量随射野大小变化规律的探讨[J].中国辐射卫生,2008,17:272-273. [14] 黄贤湛.自制铅挡块对电子线输出因子的影响[J].实用医技杂志,2006,13:965-966. [15] 吴爱敏,潘建基,张秀春.电子线输出剂量影响因素的测定与分析[J].福建医药杂志,2004,26:183-184. [16] 陶建民,胡杰,张莹,等.直线加速器电子线输出因子的影响因素和修正方法[J].上海医学,2008,31:434-437. [17] 黄晓延,钱剑扬,钟宁山,等.高能电子线射野中心轴百分深度剂量测定[J].癌症,2000,19:603-606.
2014, Vol. 23 
