Lillicrap S C, Wilson P, Boag J W
Phys Med Biol. 1975 Jan;20(1):30-8. doi: 10.1088/0031-9155/20/1/002.
In a high energy electron beam the spatial distribution of absorbed energy is dominated by multiple scattering of the electrons. The dose distribution in a broad parallel electron beam entering a uniform phantom can be resolved into a series of narrow beams overlapping one another, in each of which the scattering conditions are identical. It is therefore possible to build up a broad beam dose distribution from a knowledge of the axial and radial dose distribution in a narrow beam. Measurements have been made of such narrow beam distributions using finely collimated electron beams in the energy range 4-10 MeV, and the resulting data added by computer to give broad beam distributions which are compared with measured isodose curves. The method has been extended also to construct isodose distributions in heterogeneous phantoms. The advantages of storing electron beam data in the form of narrow beam distributions are described with particular reference to the problem of irradiating heterogeneous tissue volumes.
在高能电子束中，吸收能量的空间分布主要由电子的多次散射决定。进入均匀体模的宽平行电子束中的剂量分布可分解为一系列相互重叠的窄束，其中每一束中的散射条件都是相同的。因此，根据窄束中的轴向和径向剂量分布知识，就有可能构建出宽束剂量分布。已使用能量范围为4 - 10 MeV的细准直电子束对这种窄束分布进行了测量，并通过计算机将所得数据相加，以给出宽束分布，并与测量的等剂量曲线进行比较。该方法也已扩展到构建非均匀体模中的等剂量分布。特别针对照射非均匀组织体积的问题，描述了以窄束分布形式存储电子束数据的优点。
