Sichani B Teimouri, Sohrabpour M
Physics Department, Amir Kabir University of Technology, Tehran, IR Iran.
Phys Med Biol. 2004 Mar 7;49(5):807-18. doi: 10.1088/0031-9155/49/5/011.
The Monte Carlo transport code MCNP was used to simulate the photon beam from a Theratronics 780-C cobalt therapy unit and to calculate some dose-dependent parameters as functions of field size. The simulation process has included the source capsule, collimators (fixed and adjustable), lead in the unit head, and the field sizes as ranged from 5 x 5 to 35 x 35 cm2. Calculations have been carried out in a water phantom at a fixed source-surface distance of 80 cm. Detailed simulation of the major components of the therapy unit made it possible to calculate the effects of each unit component on the photon spectrum at the phantom surface. Percentage depth dose and peak scatter factor were evaluated for various field sizes. And tissue-air ratios were also determined for a field size of 10 x 10 cm2, as a function of depth down to 30 cm. To test the accuracy of the calculated results, they were compared with the published data of the British Journal of Radiology (BJR) suppl. 25 and good agreement between measurements and calculations has been obtained. Deviations typically were found to be of the order of 1%.
使用蒙特卡罗输运代码MCNP来模拟Theratronics 780 - C型钴治疗机发出的光子束，并计算一些与剂量相关的参数作为射野大小的函数。模拟过程包括源容器、准直器（固定和可调）、治疗机头中的铅以及从5×5到35×35 cm²的射野大小。在源皮距固定为80 cm的水模体中进行了计算。对治疗机主要部件的详细模拟使得能够计算每个部件对模体表面光子能谱的影响。评估了不同射野大小的百分深度剂量和峰值散射因子。还确定了射野大小为10×10 cm²时组织空气比与深度达30 cm的函数关系。为了检验计算结果的准确性，将其与《英国放射学杂志》（BJR）增刊25发表的数据进行了比较，测量值与计算值之间取得了良好的一致性。通常发现偏差约为1%。
