Electron Transport in Tissue-like Material

描述（由申请人提供）：本提案是对2002年7月启动的三年期资助的竞争性续期的修订。提出的薄片电子发射的研究旨在提供数据，以测试用于描述电离辐射在生物材料中能量沉积的初始空间格局的计算模型。这些初始损伤模式影响随后的化学和生物化学，影响导致生物修复、基因组不稳定、细胞凋亡和/或最终癌症诱导的关键细胞途径。我们对辐射损伤的初始模式的大部分知识都是从逐个事件的蒙特卡罗轨道模拟模型中获得的，这些模型通常在其截面数据库中包含不确定性。目前的工作，以及提议的扩展，提供了我们可以在电子传输物理水平上测试轨道模拟模型的数据，即在化学反应修改和平均之前。在最初的拨款期间，已经获得了组织的主要成分——水中电子传递的数据；SF6是一种在低能电子传递谱中具有明确结构的独特分子；并且已经获得了一些分子的初步数据，这些数据有助于评估表面键合和分子结构对电子能谱的影响，例如，数据来自固体（冷冻）CO2, C2H6, C3H6， C2F2H2和氙。碳氢化合物的持续研究正在进行中，目标技术正在开发中，以将这项工作扩展到更大的生物分子和组织。低温靶标提供了一种独特的能力来研究生物分子和组织作为温度的函数，从而作为含水量的函数。继续工作的一个主要目标是更好地理解水在生物分子和组织中电子传输中的作用。我们认为这项扩展的研究将为组织成分对电子传递的作用提供独特的见解，并提供数据，可以为电离辐射能量沉积后电子传递的演变模型提供敏感的测试。这项工作将有助于提高对传递到细胞、细胞成分和关键生物分子的局部剂量分布评估的准确性。这些结果将加强我们建立临床相关的放射治疗的努力，更好地了解对健康组织的潜在损害。

DESCRIPTION (provided by applicant): This proposal is a revised competitive renewal of a three year grant initiated in July, 2002. The proposed study of electron emission from thin foils is designed to provide data to test computational models developed to describe the initial spatial pattern of energy deposition by ionizing radiation in biologic material. These initial damage patterns affect subsequent chemistry and biochemistry that influence crucial cellular pathways leading to biological repair, genomic instability, apoptosis, and/or finally cancer induction. Much of our knowledge of the initial patterns of radiation damage is obtained from event-by-event Monte Carlo track simulation models that often contain uncertainties in their cross section database. The current work, and the proposed extension, provides data on which we can test track simulation models at the level of the physics of electron transport, i.e., prior to modification and averaging by chemical reactions. During the initial grant period data have been obtained for electron transport in water, a major constituent of tissue; SF6, a unique molecule with well defined structure in the low-energy electron transport spectra; and preliminary data have been obtained for several molecules that aid in assessment of effects of surfaces bonding and molecular structure on electron spectra, e.g., data have been derived from solid (frozen) CO2, C2H6, C3H6, C2F2H2, and Xenon. Continuing study of hydrocarbons is underway and target technology is being developed to extend this work to larger bio-molecules and tissue. The cryogenic target provides a unique capability to study bio-molecules and tissue as a function of temperature and thereby as a function of water content. A major goal of the continued work is to better understand the role of water in the transport of electrons in bio- molecules and tissue. We feel this expanded study will provide unique insight into the role of tissue constituents on electron transport, and provide data that can provide sensitive tests of evolving models of electron transport following energy deposition by ionizing radiation. This work will contribute to increased accuracy in the assessment of local dose distributions delivered to cells, cellular components, and critical biomolecules. The results will enhance our effort to establish clinically relevant radiation treatment with a better understanding of potential damage to healthy tissue.