McParland B J, Cunningham J R, Woo M K
Department of Clinical Physics, Princess Margaret Hospital, Toronto, Ontario, Canada.
Med Phys. 1988 Jul-Aug;15(4):489-97. doi: 10.1118/1.596303.
Pencil beam algorithms for the calculation of electron beam dose distributions have come into widespread use. These algorithms, however, have generally exhibited difficulties in reproducing dose distributions for small field dimensions or, more specifically, for those conditions in which lateral scatter equilibrium does not exist. The work described here has determined that this difficulty can arise from the manner in which the width of the pencil beam is calculated. A unique approach for determining the pencil beam widths required to accurately reproduce small field dose distributions in a homogeneous phantom is described and compared with measurements and the results of other calculations. This method has also been extended to calculate electron beam dose distributions in heterogeneous media and the results of this work are presented. Suggestions for further improvements are discussed.
用于计算电子束剂量分布的笔形束算法已得到广泛应用。然而，这些算法在再现小射野尺寸的剂量分布时，或者更具体地说，在不存在侧向散射平衡的条件下，通常会遇到困难。本文所述的工作已确定，这种困难可能源于笔形束宽度的计算方式。本文描述了一种独特的方法，用于确定在均匀模体中准确再现小射野剂量分布所需的笔形束宽度，并将其与测量结果及其他计算结果进行比较。该方法还被扩展用于计算非均匀介质中的电子束剂量分布，并给出了这项工作的结果。文中还讨论了进一步改进的建议。
