Mesbahi Asghar, Mehnati Parinaz, Keshtkar Ahmad, Farajollahi Alireza
Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Attare Nishabouri Street, Tabriz, Iran.
Radiat Med. 2007 Aug 1;25(7):315-24. doi: 10.1007/s11604-007-0142-6. Epub 2007 Aug 27.
The dosimetric features of an unflattened 6-MV photon beam of an Elekta SL-25 linac was calculated by the Monte Carlo (MC) method.
The head of the Elekta SL-25 linac was simulated using the MCNP4C MC code. The accuracy of the model was evaluated using measured dosimetric features, including depth dose values and dose profiles in a water phantom. The flattening filter was then removed, and beam dosimetric properties were calculated by the MC method and compared with those of the flattened photon beam.
Our results showed a significant (twofold) increase in the dose rate for all field sizes. Also, the photon beam spectra for an unflattened beam were softer, which led to a steeper reduction in depth doses. The decrease in the out-of-field dose and increase in the contamination electrons and a buildup region dose were the other consequences of removing the flattening filter.
Our study revealed that, for recent radiotherapy techniques, the use of multileaf collimators for beam shaping removing the flattening filter could offer some advantages, including an increased dose rate and decreased out-of-field dose.
采用蒙特卡罗（MC）方法计算医科达SL-25直线加速器未 flattening 的6兆伏光子束的剂量学特征。
使用MCNP4C MC代码模拟医科达SL-25直线加速器的头部。通过测量剂量学特征（包括水模中的深度剂量值和剂量分布）评估模型的准确性。然后移除 flattening 滤波器，通过MC方法计算束流剂量学特性，并与 flattening 光子束的特性进行比较。
我们的结果显示，所有射野尺寸的剂量率均显著（两倍）增加。此外，未 flattening 束的光子束谱更软，导致深度剂量下降更陡峭。移除 flattening 滤波器的其他后果是野外剂量降低、污染电子增加以及建成区剂量增加。
我们的研究表明，对于近期的放射治疗技术，使用多叶准直器进行束流整形并移除 flattening 滤波器可能具有一些优势，包括剂量率增加和野外剂量降低。
Zotero 插件