Jabbari Keyvan, Anvar Hossein Saberi, Tavakoli Mohammad Bagher, Amouheidari Alireza
Department of Medical Physics and Engineering, School of Medicine, Medical Image & Signal Processing Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
Department of Radiation-Oncology, Isfahan Milad Hospital, Isfahan, Iran.
J Med Signals Sens. 2013 Jul;3(3):172-9.
The Monte Carlo method is the most accurate method for simulation of radiation therapy equipment. The linear accelerators (linac) are currently the most widely used machines in radiation therapy centers. In this work, a Monte Carlo modeling of the Siemens ONCOR linear accelerator in 6 MV and 18 MV beams was performed. The results of simulation were validated by measurements in water by ionization chamber and extended dose range (EDR2) film in solid water. The linac's X-ray particular are so sensitive to the properties of primary electron beam. Square field size of 10 cm × 10 cm produced by the jaws was compared with ionization chamber and film measurements. Head simulation was performed with BEAMnrc and dose calculation with DOSXYZnrc for film measurements and 3ddose file produced by DOSXYZnrc analyzed used homemade MATLAB program. At 6 MV, the agreement between dose calculated by Monte Carlo modeling and direct measurement was obtained to the least restrictive of 1%, even in the build-up region. At 18 MV, the agreement was obtained 1%, except for in the build-up region. In the build-up region, the difference was 1% at 6 MV and 2% at 18 MV. The mean difference between measurements and Monte Carlo simulation is very small in both of ONCOR X-ray energy. The results are highly accurate and can be used for many applications such as patient dose calculation in treatment planning and in studies that model this linac with small field size like intensity-modulated radiation therapy technique.
蒙特卡罗方法是模拟放射治疗设备最精确的方法。直线加速器（linac）是目前放射治疗中心使用最广泛的设备。在这项工作中，对西门子ONCOR直线加速器在6兆伏和18兆伏射束下进行了蒙特卡罗建模。模拟结果通过在水中使用电离室测量以及在固体水中使用扩展剂量范围（EDR2）胶片测量进行了验证。直线加速器的X射线特性对初级电子束的性质非常敏感。将由准直器产生的10厘米×10厘米方形射野尺寸与电离室和胶片测量结果进行了比较。使用BEAMnrc进行机头模拟，使用DOSXYZnrc进行剂量计算以用于胶片测量，并使用自制的MATLAB程序分析DOSXYZnrc生成的3ddose文件。在6兆伏时，蒙特卡罗建模计算的剂量与直接测量之间的一致性在最宽松的情况下达到1%，即使在剂量建成区也是如此。在18兆伏时，除剂量建成区外，一致性达到1%。在剂量建成区，6兆伏时差异为1%，18兆伏时差异为2%。在两种ONCOR X射线能量下，测量值与蒙特卡罗模拟之间的平均差异都非常小。结果高度精确，可用于许多应用，如治疗计划中的患者剂量计算以及在诸如调强放射治疗技术等小射野尺寸模拟该直线加速器的研究中。
