Mandour M A, Nüsslin F, Harder D
Acta Radiol Suppl. 1983;364:43-8.
Narrow electron beams with approximately Gaussian radial fluence distributions were extracted from a clinical 42 MeV betatron by means of a special multi-diaphragm lead collimator with either 3 or 7.5 mm diameter of the effective diaphragm. From each narrow beam the dose distribution in water, was measured with an automated scanning system, and the corresponding dose distribution of the point monodirectional source was obtained by deconvolution. As a reference, the fluence distribution in air at the same distance z was used, corrected for multiple scattering in air where necessary. At 10, 20 and 40 MeV, non-linear pear-shaped curves for the root mean square radial excursion, sigma(z), as functions of the depth, with maxima of 12, 19.7 and 27.8 mm at about 70 per cent of the practical range were obtained. The second characteristic function, I(z), the integral of the dose over the transverse plane at depth z, was obtained from the measured broad beam depth dose curve and the associated transverse dose distributions.
利用一种特殊的多隔板铅准直器，从一台临床用42兆电子伏特电子感应加速器中引出径向注量分布近似为高斯分布的窄电子束，该准直器的有效隔板直径为3毫米或7.5毫米。使用自动扫描系统测量了每个窄束在水中的剂量分布，并通过去卷积获得了点单向源的相应剂量分布。作为参考，使用了在相同距离z处空气中的注量分布，并在必要时对空气中的多次散射进行了校正。在10兆电子伏特、20兆电子伏特和40兆电子伏特时，均获得了均方根径向偏移量σ(z)随深度变化的非线性梨形曲线，在实际射程的约70%处，其最大值分别为12毫米、19.7毫米和27.8毫米。第二个特征函数I(z)，即深度z处横截面上剂量的积分，是从测量的宽束深度剂量曲线和相关的横向剂量分布中获得的。
