Efficiency improvements of x-ray simulations in EGSnrc user-codes using bremsstrahlung cross-section enhancement (BCSE)
Efficiency improvements of x-ray simulations in EGSnrc user-codes using bremsstrahlung cross-section enhancement (BCSE)
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DOI：
10.1118/1.2736778
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发表时间：
2007-06-01
期刊：
影响因子：
3.8
通讯作者：
Rogers, D. W. O.
中科院分区：
文献类型：
--
作者：
Ali, E. S. M.;Rogers, D. W. O.
本文介绍了实施韧致辐射截面增强（BCSE）方差减少技术到EGSnrc/BEAMnrc系统。BCSE使得从韧致辐射目标产生X射线的模拟更有效;它通过人为地使韧致辐射的罕见事件更丰富来实现这一点，这增加了独立光子的数量，有助于减少感兴趣的量的方差，而不明显增加CPU时间。BCSE不会干扰EGSnrc中的带电粒子输运，并且它与EGSnrc和BEAMnrc中已经使用的所有其他方差减小技术兼容，包括范围抑制，均匀韧致辐射分裂和定向韧致辐射分裂。当最佳地将BCSE与分裂相结合以模拟医学物理研究和临床实践中感兴趣的典型情况时，效率可以比模拟模拟获得的效率高出五个数量级，并且比单独优化分裂获得的效率高出整整一个数量级（这是本研究进行之前EGSnrc/BEAMnrc系统的最新技术水平）。这项研究建议，BCSE与现有的分裂技术相结合的所有EGSnrc/BEAMnrc模拟，涉及韧致辐射的目标，无论是在千伏和兆伏范围。推荐了诊断X射线成像和放射治疗中典型情况下的最佳横截面增强因子，沿着一种简单的模拟优化算法。(c)2007年美国医学物理学家协会。
This paper presents the implementation of the bremsstrahlung cross-section enhancement (BCSE) variance-reduction technique into the EGSnrc/BEAMnrc system. BCSE makes the simulation of x-ray production from bremsstrahlung targets more efficient; it does so by artificially making the rare event of bremsstrahlung emission more abundant, which increases the number of statisticallyindependent photons that contribute to reducing the variance of the quantity of interest without increasing the CPU time appreciably. BCSE does not perturb the charged-particle transport in EGSnrc and it is made compatible with all other variance-reduction techniques already used in EGSnrc and BEAMnrc, including range rejection, uniform bremsstrahlung splitting, and directional bremsstrahlung splitting. When optimally combining BCSE with splitting to simulate typical situations of interest in medical physics research and in clinical practice, efficiencies can be up to five orders of magnitude larger than those obtained with analog simulations, and up to a full order of magnitude larger than those obtained with optimized splitting alone (which is the state-of-the-art of the EGSnrc/BEAMnrc system before this study was carried out). This study recommends that BCSE be combined with the existing splitting techniques for all EGSnrc/BEAMnrc simulations that involve bremsstrahlung targets, both in the kilovoltage and megavoltage range. Optimum cross-section enhancement factors for typical situations in diagnostic x-ray imaging and in radiotherapy are recommended, along with an easy algorithm for simulation optimization. (c) 2007 American Association of Physicists in Medicine.