Gudowska Irena, Sobolevsky Nikolai, Andreo Pedro, Belkić Dzevad, Brahme Anders
Division of Medical Radiation Physics, Karolinska Institutet and Stockholm University, PO Box 260, S-171 76 Stockholm, Sweden.
Phys Med Biol. 2004 May 21;49(10):1933-58. doi: 10.1088/0031-9155/49/10/008.
The development of the Monte Carlo code SHIELD-HIT (heavy ion transport) for the simulation of the transport of protons and heavier ions in tissue-like media is described. The code SHIELD-HIT, a spin-off of SHIELD (available as RSICC CCC-667), extends the transport of hadron cascades from standard targets to that of ions in arbitrary tissue-like materials, taking into account ionization energy-loss straggling and multiple Coulomb scattering effects. The consistency of the results obtained with SHIELD-HIT has been verified against experimental data and other existing Monte Carlo codes (PTRAN, PETRA), as well as with deterministic models for ion transport, comparing depth distributions of energy deposition by protons, 12C and 20Ne ions impinging on water. The SHIELD-HIT code yields distributions consistent with a proper treatment of nuclear inelastic collisions. Energy depositions up to and well beyond the Bragg peak due to nuclear fragmentations are well predicted. Satisfactory agreement is also found with experimental determinations of the number of fragments of a given type, as a function of depth in water, produced by 12C and 14N ions of 670 MeV u(-1), although less favourable agreement is observed for heavier projectiles such as 16O ions of the same energy. The calculated neutron spectra differential in energy and angle produced in a mimic of a Martian rock by irradiation with 12C ions of 290 MeV u(-1) also shows good agreement with experimental data. It is concluded that a careful analysis of stopping power data for different tissues is necessary for radiation therapy applications, since an incorrect estimation of the position of the Bragg peak might lead to a significant deviation from the prescribed dose in small target volumes. The results presented in this study indicate the usefulness of the SHIELD-HIT code for Monte Carlo simulations in the field of light ion radiation therapy.
描述了用于模拟质子和重离子在类组织介质中传输的蒙特卡罗代码SHIELD-HIT（重离子传输）的开发。代码SHIELD-HIT是SHIELD（可作为RSICC CCC-667获得）的衍生版本，它将强子级联传输从标准靶扩展到任意类组织材料中的离子传输，同时考虑了电离能量损失离散和多次库仑散射效应。已将SHIELD-HIT获得的结果与实验数据、其他现有蒙特卡罗代码（PTRAN、PETRA）以及离子传输的确定性模型进行了验证，比较了质子、12C和20Ne离子撞击水时能量沉积的深度分布。SHIELD-HIT代码产生的分布与核非弹性碰撞的适当处理一致。对由于核裂变导致的直至布拉格峰及远超过布拉格峰的能量沉积进行了很好的预测。对于给定类型碎片的数量作为水中深度的函数，由670 MeV u(-1)的12C和14N离子产生的情况，实验测定结果也与计算结果达成了令人满意的一致，尽管对于相同能量的较重射弹如16O离子，一致性稍差。用290 MeV u(-1)的12C离子辐照模拟火星岩石时产生的能量和角度微分的计算中子谱也与实验数据显示出良好的一致性。得出的结论是，对于放射治疗应用，有必要仔细分析不同组织的阻止本领数据，因为布拉格峰位置的错误估计可能导致小靶体积中与规定剂量的显著偏差。本研究给出的结果表明SHIELD-HIT代码在轻离子放射治疗领域进行蒙特卡罗模拟时是有用的。
