MULTIPLE SCATTERING THEORY APPLIED TO ELECTRON DOSIMETRY

电子束越来越多地用于放射治疗 因为它们的快速剂量下降最大限度地减少了 超出目标体积的关键健康组织。 不幸的是，对于 治疗计划的目的，它还不可能计算 精确的吸收剂量分布，特别是在存在 组织不均匀性和身体弯曲。 在穿透身体时， 高能电子遭受大量碰撞， 虽然主要是向前，路径。只是最近，一些 研究人员已经开始应用费米-艾格斯多重散射理论， 电子剂量学的问题，认识到这一理论描述了 电子束的行为作为一个合理的第一近似，在 至少在均匀或水平分层介质中。 才是目的 提出的研究，以发展和应用费米-艾格斯理论的方式， 这允许精确计算电子剂量分布在 组织不均匀性和身体弯曲的存在直接使用 计算机断层扫描（CT）数据。 目标是实现一个 在实际计算中， 可能遇到的最复杂情况下的电子剂量 临床上 建议的研究方法是发展费米-Eyges理论， 一个高精度，以简化它的数学到一个实际的 计算算法，并完善和验证算法，通过 实验 理论工作的关键是概念 代表性的电子路径，此外，将有必要 在计算算法中包括多个次级效应，这些次级效应 被费米-艾格斯理论忽略了 对于实验工作，四个 幻影提供逐渐更复杂的配置， 将使用不均匀性;整个体模的剂量分布 将记录在射线照相胶片上，热释光剂量测定 (TLD)将用于保持胶片剂量测定的准确性。 CT 扫描将用于描述更复杂的体模配置 到计算算法。

Electron beams are increasingly coming into use in the radiation treatment of cancer, because their rapid dose falloff minimizes irradiation of critical healthy tissues beyond the target volume. Unfortunately, for treatment planning purposes it is not yet possible to calculate the absorbed dose distribution precisely, particularly in the presence of tissue inhomogeneities and body curvature. In penetrating the body, high-energy electrons suffer a great many collisions and follow a tortuous, although mainly forward, path. It has only been recently that a number of investigators have begun to apply Fermi-Eyges multiple scattering theory to the problem of electron dosimetry, recognizing that this theory describes the behaviour of the electron beam as a reasonable first approximation, at least in a homogeneous or horizontally layered medium. It is the purpose of the proposed research to develop and apply Fermi-Eyges theory in a way which allows the accurate calculation of electron dose distributions in the presence of tissue inhomogeneities and body curvature using directly the data from computerized tomography (CT) scans. The goal is to achieve an accuracy of 5%, and preferably of 3%, in the practical calculation of electron dose in the most complicated situations likely to be encountered clinically. The method of the proposed research is to develop the Fermi-Eyges theory to a high accuracy, to simplify it mathematically into a practical computational algorithm, and to refine and verify the algorithm through experiments. The key to the theoretical work is the concept of representative electron path, and in addition it will be necessary to include in the computational algorithm a number of secondary effects which are ignored by Fermi-Eyges theory. For the experimental work, four phantoms providing progressively more complicated configurations of inhomogeneities will be use; the dose distribution throughout the phantom will be recorded on radiographic film, and thermoluminescent dosimetry (TLD) will be used to maintain the accuracy of the film dosimetry. CT scans will be used to describe the more complicated phantom configurations to the computational algorithm.