EXTENSION OF A 3-D DOSE FIELD MODEL

计算由以下因素产生的吸收剂量分布的能力 光子束和电子束的最一般的特性是 在放射治疗中至关重要。 从概念上讲，这个新的辐射场 模型以经验分布为基础，沿沿着三个相互 在“主字段”中的垂直参考线和数学 表达式来描述的影响，如果变化的领域大小，深度和 焦距 该概念被应用于射束修改装置， 好. 该方法从理论上和实践上都很有吸引力 的观点 研究包括不规则的推广 由用于光子束和电子束的不规则块修改的场， 以及不均匀性的影响。 描述的新发展 的沿射线分布以及场大小的依赖性， 正在实施射束轮廓。 电子束的延伸是 继续。 特别令人感兴趣的是， 电子能量和需要灵活应用不同的 能量和场的形状与光子场的结合。 中央 射线分布现在可以描述的基础上只有七个 特征性深度剂量数据点，60 Co至18 MV X射线，使用 净部分深度剂量（NFD）。 NFD形式主义目前 被扩展到不均匀性的影响的描述，如 肺组织。

The capability to calculate the distribution of absorbed dose produced by photon beams and electron beams of the most general characteristics is of vital importance in radiotherapy. Conceptually, this new radiation field model takes as a basis the empirical distributioins along three mutually perpendicular reference lines in a "master field" and mathematical expressions to describe the effect if variations of field size, depth and focal distance. This concept is applied to the beam-modifying devices as well. The approach is attractive from a theoretical as well as a practical point of view. The investigations include the generalization for irregular fields modified by irregular blocks for photon beams and electron beams, and the influence of inhomogeneities. New developments in the description of the along-the-ray distirbution as well as the field size dependence of the beam profile are being implemented. The extension to electron beams is continuing. Of special interest are the implications of the large number of electron energies and the need for flexible application of different energies and field shapes in conbination with photon fields. The central ray distributions can now be described on the basis of only seven charactertistic depth dose data points, for 60Co to 18 MV x-rays, using the concept of Net Fractional Depth Dose (NFD). The NFD formalism is currently being extended to the description of the influence of inhomogeneities, such as lung tissue.