Laboratoire de Physique Moléculaire et des Collisions, Université Paul Verlaine-Metz, France.
Int J Radiat Biol. 2012 Jan;88(1-2):54-61. doi: 10.3109/09553002.2011.641451.
We describe here a novel full-differential Monte Carlo (MC) event-by-event simulation, for modelling electron and positron histories in liquid and gaseous water, with impact energies ranging from the water excitation threshold (7.4 eV) to 10 keV. This new track-structure code is named EPOTRAN, an acronym for Electron and POsitron TRANsport in water.
All the processes induced by both electrons and positrons are studied in detail via theoretical differential and total cross sections, calculated within the quantum mechanical framework by using the partial-wave method. Elastic and inelastic interactions are then successively reviewed, including in particular an original description of the positron-induced capture process leading to Positronium formation.
Total and differential cross sections are reported and compared with a large set of existing measurements. Rather good agreement is generally observed over the considered energy range.
This work reports the theoretical cross sections used in a special purpose Monte Carlo simulation suitable for electron and positron transport in gaseous and liquid water. This MC code should represent an accurate tool for dose calculation at the nanometric scale, by providing a detailed spatial distribution of energy deposits. Furthermore, positron trajectory studies made possible by this approach should prove useful for evaluating the real contribution of the positron range on the overall spatial resolution of PET (Positron Emission Tomography) imaging.
我们在此描述了一种新颖的全微分蒙特卡罗（MC）事件驱动模拟方法，用于模拟液体和气体水中电子和正电子的历史，其影响能量范围从水激发阈值（7.4eV）到 10keV。这个新的轨迹结构代码被命名为 EPOTRAN，是电子和 POsitron 在水中 TRANsport 的缩写。
通过理论微分和总截面，在量子力学框架内使用分波方法计算，详细研究了所有由电子和正电子引起的过程。然后，相继回顾了弹性和非弹性相互作用，特别是包括了导致正电子素形成的正电子诱导俘获过程的原始描述。
报告了总截面和微分截面，并与大量现有的测量结果进行了比较。在考虑的能量范围内，通常观察到相当好的一致性。
这项工作报告了在特殊用途的蒙特卡罗模拟中使用的理论截面，适用于气态和液态水中的电子和正电子传输。这个 MC 代码应该代表一种在纳米尺度上进行剂量计算的精确工具，通过提供能量沉积的详细空间分布。此外，通过这种方法进行的正电子轨迹研究应该有助于评估正电子射程对 PET（正电子发射断层扫描）成像整体空间分辨率的实际贡献。
