Review of theories on ionization in fast ion-atom collisions with prospects for applications to hadron therapy
Review of theories on ionization in fast ion-atom collisions with prospects for applications to hadron therapy
复制标题
快速离子原子碰撞电离理论综述及其在强子治疗中的应用前景
DOI：
10.1007/s10910-010-9662-x
复制
发表时间：
2010
影响因子：
1.7
通讯作者：
D. Belkić
中科院分区：
文献类型：
--
作者：
D. Belkić
这项研究强调需要一个系统的和深入的联系在高能离子碰撞的量子理论的进展和应用强子治疗。快速离子束的散射理论已经达到了它的发展阶段，准确和鲁棒适用的方法可以有利地出口到应用领域，如空间研究，聚变能计划，医学等，特别是在高能量的扭曲波碰撞理论很容易提供总的，部分和完全微分截面的非弹性碰撞的离子弹丸与任何目标系统。通过大量的测试，发现这种理论截面与原子靶的实验数据非常吻合。这些方法的分子目标的适当扩展也完成了计算工作，大约相当于多电子原子目标。这是通过使用任何分子靶点的标准Slater型原子基函数来完成的，包括与强子治疗相关的组织等效材料（例如水）。这种专业知识需要通过离子传输物理学带到医学中，其中最常用的是粗布拉格求和规则，用于获得作为原子截面线性组合的分子截面。相对论性扭曲波理论也是可用的，但目前还没有用于模拟相对论性离子通过组织的通道，因为需要在深部肿瘤的强子治疗。扭曲波散射理论在裸离子与水分子快速碰撞中的应用已经成熟。这种类型的应用程序将提供最准确的数据库的各种横截面（电子捕获，激发，电离等），可以用作可靠的入口数据，随后的Monte Carlo模拟的能量损失的离子通过组织期间。为了提高整体效率，这些理论截面可以在足够密集的多变量网格上预先计算，从而在随机模拟期间产生有利的直接采样模块。这样一个全面的战略可以提供准确和有效的算法，将纳入国家的最先进的方法，从高能原子散射理论，涉及离子束。这是目前强子疗法的物理学部分所缺少的，因为所有主要的蒙特卡罗代码通常都采用原子截面数据库，这些数据库几乎完全依赖于贝特-布洛赫公式和一些唯象表达式，这些表达式的拟合参数根据有限的实验数据集进行调整。至关重要的是，需要强调引入一个仍然缺少的蒙特卡罗代码，可以模拟运输的离子与二次电子在组织中。目前主要的蒙特卡罗程序模拟离子或电子的传输，但不能同时模拟两者。然而，高能离子通过密集地电离穿过的组织而产生大量电子，并且它们中的许多是δ电子，即，它们自身能够电离各种靶。由于它们的轻质量和相当大的能量，δ电子经历多次散射。由于这种累积效应，在经离子疗法处理的组织的DNA分子的所有双链断裂中，约70%是由δ电子产生的。因此，有必要模拟由初级离子束产生的δ电子的输运。这种类型的计算是目前缺少的主要离子输运代码。总的来说，这项工作彻底分析了领先的量子力学扭曲波理论的概念和计算的进展，旨在应用于医学的高能离子碰撞。同时指出了与强子治疗相关的快重离子碰撞理论的医学与基础研究之间的交叉研究的主要战略方向。
This study emphasizes the need for a systematic and in-depth connection between the progress in quantum theory of energetic ion collisions and applications to hadron therapy. Scattering theory for fast ion beams has reached its stage of development where accurate and robustly applicable methodologies can advantageously be exported to applied fields such as space research, fusion energy program, medicine, etc. In particular, distorted wave collision theories at high energies readily provide total, partial and fully differential cross sections for inelastic collisions of ionic projectiles with any target system. By numerous and thorough testings, such theoretical cross sections were found to exhibit excellent agreement with experimental data on atomic targets. Adequate extensions of these methods to molecular targets were also accomplished with computational efforts that are approximately comparable to that for multi-electron atomic targets. This was done by using the standard Slater-type atomic basis functions for any molecular targets, including tissue-equivalent materials (e.g. water) of relevance to hadron therapy. This expertize needs to be brought to medicine through ion transport physics, which most frequently employs the crude Bragg sum rule for obtaining molecular cross sections as linear combination of atomic cross sections. Relativistic distorted wave theories are also available, but not currently in use for modeling the passage of relativistic ions through tissue, as needed in hadron therapy of deep-seated tumors. It is high time for extensive and thorough applications of the well-established distorted wave scattering theories to fast collisions of bare and partially clothed multiple charged ions with water molecule. This type of application would provide the most accurate data bases for various cross sections (on electron capture, excitation, ionization, etc) that can be used as reliable entry data for subsequent Monte Carlo simulations of energy losses of ions during their passage through tissue. In order to gain in overall efficiency, these theoretical cross sections could be precomputed at sufficiently dense multi-variable grids, thus yielding modules for advantageous direct sampling during stochastic simulations. Such a comprehensive strategy could provide both accurate and efficient algorithms that would incorporate the state-of-the-art methodologies from high-energy atomic scattering theory involving ion beams. This is currently missing in the physics part of hadron therapy, since all the major Monte Carlo codes customarily employ atomic cross section data bases that rely almost exclusively upon the Bethe–Bloch formula and some phenomenological expressions with fitting parameters adjusted to the limited sets of experimental data. Crucially, the need is emphasized for the introduction of a still missing Monte Carlo code which could simulate transport of ions together with secondary electrons in tissue. The current main Monte Carlo codes simulate transport of either ions or electrons, but not both simultaneously. However, energetic ions produce a large number of electrons by densely ionizing the traversed tissue and many of them are δ-electrons i.e. capable on their own of ionizing various targets. Due to their light mass and considerable energy, δ-electrons undergo multiple scatterings. Because of this cumulative effect, among all the double strand breaks of DNA molecules of tissue treated by ion therapy, some 70% are produced by δ-electrons. Hence the necessity to simulate transport of δ-electrons produced by primary ion beams. Such types of computations are presently missing from the major ion transport codes. Overall, this work thoroughly analyzes conceptual and computational advances of the leading quantum-mechanical distorted wave theories for energetic ion collisions aimed at applications to medicine. Additionally, the main strategic directions are also indicated to further cross-disciplinary fertilization between medicine and basic research on collision theory of fast heavy ions of relevance to hadron therapy.
影响因子：
3.8
作者：
Parodi, Katia;Paganetti, Harald;Bortfeld, Thomas
通讯作者：
Bortfeld, Thomas