摘要
目的：基于IAEA Varian 6 MV X线相空间文件和目标机头的光子能谱分布，建立一种新的蒙特卡罗模拟方法，重建医用加速器机头模型及X射线能量的能谱。方法对已验的6 MV X线相空间文件进行预处理，提升每个粒子能量；根据位置、能量不同将粒子保存到不同的Phase？Space？Let （ PSL）文件中，得到初始目标能量加速器机头的蒙特卡罗模拟的初始光子能谱；然后对某一待验目标能量（医科达PRECISE 10 MV X线）加速器机头的光子能谱，用初始光子能谱拟合得到拟合系数，即每个PSL的权重；最后使用初始PSL文件和该权重信息重建出待验目标能量的加速器机头模型，对其不同开野进行中轴PDD分布的计算，并用一维γ通过率验证该方法的有效性。结果重建的10 MV光子能谱与已验的10 MV能谱峰值位置相同，整体分布一致；由重建的10 MV机头模型计算得到的PDD与实测的吻合度较高，一维γ通过率（参数1 mm 1％，Threshold＝0％）＞96％。结论笔者提出的蒙特卡罗重建方法可靠、准确有效。
Objective To establish a novel Monte Carlo simulation method for reconstruction of medical accelerator model and X-ray energy spectrum based on IAEA Varian 6 MV X-ray phase-space file and photon energy spectrum of the target accelerator. Methods The verified 6 MV X-ray phase-space files were preprocessed to elevate the energy of each particle. Particles were saved in different Phase-Space-Let （ PSL） files according to their position and energy, yielding an initial photon energy spectrum for Monte Carlo simulation of accelerator under an initial target energy. The initial photon energy spectrum was fit to a photon energy spectrum of an accelerator （ Elekta Precise 10 MV X-ray accelerator） under an unknown target energy to yield a fitting coefficient, which was the weight of each PSL. Finally, an accelerator model under an unknown target energy was reconstructed using the initial PSL files and the weight information. The percentage depth dose （ PDD） distribution was calculated in different square open fields. The effectiveness of this method was verified using one dimensional gamma passing rate. Results The peak position and overall distribution of the reconstructed 10 MV photon energy spectrum were in accordance with those of the verified 10 MV photon energy spectrum. The PDD calculated from the reconstructed 10 MV accelerator model agreed well with the measured PDD. The one-dimensional gamma passing rate was above 96%（ 1%/1 mm, threshold=0%） . Conclusion The Monte Carlo reconstruction method proposed in this study is reliable, accurate, and effective.
出处
《中华放射肿瘤学杂志》
CSCD
北大核心
2016年第8期847-850,共4页
Chinese Journal of Radiation Oncology
基金
上海市卫生和计划生育委员会重大项目（201540032）
