Lewis R D, Ryde S J, Hancock D A, Evans C J
Department of Medical Physics and Clinical Engineering, Singleton Hospital, Swansea, UK.
Phys Med Biol. 1999 May;44(5):1219-30. doi: 10.1088/0031-9155/44/5/010.
The Monte Carlo N-Particle radiation transport computer code (MCNP) has been employed on a personal computer to develop a simple model simulating the major components within the beam path of a linear accelerator radiation head, namely the electron target, primary conical collimator, beam flattening filter, wedge filter and the secondary collimators. The model was initially used to calculate the energy spectra and angular distributions of the x-ray beam for the Philips SL 75/5 linear accelerator, in a plane immediately beneath the flattening filter. These data were subsequently used as a 'source' of x-rays at the target position, to assess the emergent beam from the secondary collimators. The depth dose distributions and dose profiles at constant depth for various field sizes have been calculated for a nominal operating potential of 4 MV and found to be within acceptable limits. It is concluded that the technique may be used to calculate the energy spectra of any linear accelerator upon specification of the component dimensions, materials and nominal accelerating potential. It is anticipated that this work will serve as the basis of a quality control tool for linear accelerators and treatment planning systems.
蒙特卡罗N粒子辐射输运计算机代码（MCNP）已在个人计算机上使用，以开发一个简单模型，模拟直线加速器辐射头束流路径中的主要部件，即电子靶、初级锥形准直器、束流均整滤过器、楔形滤过器和次级准直器。该模型最初用于计算飞利浦SL 75/5直线加速器在均整滤过器正下方平面内X射线束的能谱和角分布。这些数据随后被用作靶位置处X射线的“源”，以评估来自次级准直器的出射束。对于4 MV的标称工作电位，已计算了各种射野大小在恒定深度处的深度剂量分布和剂量剖面，结果发现其在可接受范围内。得出的结论是，在指定部件尺寸、材料和标称加速电位后，该技术可用于计算任何直线加速器的能谱。预计这项工作将成为直线加速器和治疗计划系统质量控制工具的基础。
