An MCNPX Monte Carlo model of a discrete spot scanning proton beam therapy nozzle
An MCNPX Monte Carlo model of a discrete spot scanning proton beam therapy nozzle
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DOI：
10.1118/1.3476458
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发表时间：
2010-09-01
期刊：
影响因子：
3.8
通讯作者：
Titt, Uwe
中科院分区：
文献类型：
--
作者：
Sawakuchi, Gabriel O.;Mirkovic, Dragan;Titt, Uwe
目的：本研究的目的是验证一个离散点扫描质子束喷嘴使用蒙特卡罗（MC）代码MCNPX和使用MC验证模型调查的影响，一个低剂量的信封，它围绕着束的中心轴，对测量的积分深度剂量（IDD）profiles.Methods的离散点扫描束喷嘴的精确模型从得克萨斯大学M。D.安德森癌症中心（休斯顿，得克萨斯州）是根据喷嘴制造商提供的蓝图开发的。作者使用MCNPX源代码中的标准多次库仑散射（MCS）算法和MCNPX源代码中实现的新MCS算法对各种能量的单质子笔形束进行了模拟。通过比较计算的单个笔形射束的空气和水中横向分布和百分比深度剂量分布与其相应的测量值，验证了MC模型。然后通过比较计算的和测量的三维（3-D）剂量分布进一步测试模型。最后，IDD的配置文件进行了计算与不同的评分半径，以确定使用市售的平面平行电离室来测量IDD.Results的限制：协议的距离，定义为最近的位置之间的距离的两个等效分布具有相同的剂量值，测量和模拟的范围是在0.13厘米的MCS算法。对于低和中等笔形波束能量，使用标准MCS算法的MC模拟与测量结果更一致。相反，新的MCS算法产生了更好的结果为高能量的单笔形波束。IDD档案计算与圆柱形吻合面积相当于面积的最大的市售电离室显示高达7.8%低估的积分剂量在某些深度的IDD profile.Conclusions：作者得出结论，MCS算法的组合需要准确地再现实验数据的单笔束和3-D剂量分布的扫描束喷嘴。此外，MC模拟表明，由于低剂量包层，半径高达4.08厘米的电离室不足以准确测量扫描束喷嘴中221.8 MeV笔形束的IDD分布。(C)2010年美国医学物理学家协会。[DOI 10.1118/1.3476458]
Purpose: The purposes of this study were to validate a discrete spot scanning proton beam nozzle using the Monte Carlo (MC) code MCNPX and use the MC validated model to investigate the effects of a low-dose envelope, which surrounds the beam's central axis, on measurements of integral depth dose (IDD) profiles.Methods: An accurate model of the discrete spot scanning beam nozzle from The University of Texas M. D. Anderson Cancer Center (Houston, Texas) was developed on the basis of blueprints provided by the manufacturer of the nozzle. The authors performed simulations of single proton pencil beams of various energies using the standard multiple Coulomb scattering (MCS) algorithm within the MCNPX source code and a new MCS algorithm, which was implemented in the MCNPX source code. The MC models were validated by comparing calculated in-air and in-water lateral profiles and percentage depth dose profiles for single pencil beams with their corresponding measured values. The models were then further tested by comparing the calculated and measured three-dimensional (3-D) dose distributions. Finally, an IDD profile was calculated with different scoring radii to determine the limitations on the use of commercially available plane-parallel ionization chambers to measure IDD.Results: The distance to agreement, defined as the distance between the nearest positions of two equivalent distributions with the same value of dose, between measured and simulated ranges was within 0.13 cm for both MCS algorithms. For low and intermediate pencil beam energies, the MC simulations using the standard MCS algorithm were in better agreement with measurements. Conversely, the new MCS algorithm produced better results for high-energy single pencil beams. The IDD profile calculated with cylindrical tallies with an area equivalent to the area of the largest commercially available ionization chamber showed up to 7.8% underestimation of the integral dose in certain depths of the IDD profile.Conclusions: The authors conclude that a combination of MCS algorithms is required to accurately reproduce experimental data of single pencil beams and 3-D dose distributions for the scanning beam nozzle. In addition, the MC simulations showed that because of the low-dose envelope, ionization chambers with radii as large as 4.08 cm are insufficient to accurately measure IDD profiles for a 221.8 MeV pencil beam in the scanning beam nozzle. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3476458]