Correlated histogram representation of Monte Carlo derived medical accelerator photon-output phase space.
Correlated histogram representation of Monte Carlo derived medical accelerator photon-output phase space.
复制标题
蒙特卡罗导出的医疗加速器光子输出相空间的相关直方图表示。
DOI：
10.1118/1.598613
复制
发表时间：
1999
期刊：
影响因子：
3.8
通讯作者：
Mohan,R
中科院分区：
文献类型：
--
作者：
SchachvonWittenau,AE;Cox,LJ;BergstromJr,PM;Chandler,WP;HartmannSiantar,CL;Mohan,R
本文提出了一种对医用加速器蒙特卡罗模拟得到的光子能量和角分布进行压缩的方法。该方法将输出表示为一系列相关直方图，因此非常适合作为蒙特卡罗代码的光子源包，用于确定光子远程治疗中的剂量分布。该方法解释了轫致辐射靶中产生的辐射以及加速器头内各种处理机部件散射的辐射随距离光束中心轴的增加而产生的光子能谱分布的等心平面变化。将该算法计算的等中心能量影响与底层全物理蒙特卡罗光子相空间的能量影响进行比较，表明在一定的开场尺寸范围内，能量影响误差小于最大能量影响的1%。下颌边缘半影的比较表明，光子的角度分布得到了准确的再现。对于开放的10×10场，该算法的蒙特卡罗采样效率（产生的光子清除准直器颚的比例）约为83%，对于开放的40×40场，该算法的蒙特卡罗采样效率约为96%。在给定能量下，典型的医疗加速器的数据文件大小约为150 kB，而底层全物理相空间文件的大小为1 GB。
We present a method for condensing the photon energy and angular distributions obtained from Monte Carlo simulations of medical accelerators. This method represents the output as a series of correlated histograms and as such is well‐suited for inclusion as the photon‐source package for Monte Carlo codes used to determine the dose distributions in photon teletherapy. The method accounts for the isocenter‐plane variations of the photon energy spectral distributions with increasing distance from the beam central axis for radiation produced in the bremsstrahlung target as well as for radiation scattered by the various treatment machine components within the accelerator head. Comparison of the isocenter energy fluence computed by this algorithm with that of the underlying full‐physics Monte Carlo photon phase space indicates that energy fluence errors are less than 1% of the maximum energy fluence for a range of open‐field sizes. Comparison of jaw‐edge penumbrae shows that the angular distributions of the photons are accurately reproduced. The Monte Carlo sampling efficiency (the fraction of generated photons which clear the collimator jaws) of the algorithm is approximately 83% for an open 10×10 field, rising to approximately 96% for an open 40×40 field. Data file sizes for a typical medical accelerator, at a given energy, are approximately 150 kB, compared to the 1 GB size of the underlying full‐physics phase space file.