An empirical model for small circular electron fields was developed. This can be of great help in the treatment planning process for small circular electron fields. A complete dosimetric analysis of the circular fields defined by electron cutouts diameters (2 cm–9 cm) was done for nominal electron energies ranging between 6 MeV and 20 MeV using a 3D water phantom and a pin-point ion chamber. Properties studied included depth dose, in-air inverse-square fall-off, and beam profiles. The Varian Clianc 2100 C accelerator was modelled, benchmarked and Monte Carlo simulations were performed using the EGSnrc/BEAMnrc code for the small circular cutouts. A simple exponential model was found to accurately predict the very important therapeutic depth (90% of Dmax) for the small circular field size within an accuracy of better than 2 mm in most cases. The model has only two parameters (d₉₀ and ‘b’). Also, the penumbra widths (90% of the off-axis profiles) of these small circular electron fields were studied and least square fitted to a simple quadratic model. Full dosimetric profiles of these small circular electron fields were further studied using the benchmarked Monte Carlo simulations. This study presents a simple model to predict the very important therapeutic depth (90% of Dmax) and a recipe to develop such an electron treatment model for any linear accelerator system. Such predictions can be extremely valuable and time saving prior to treatment planning involving not only small circular shaped electron fields but also irregularly shaped electron fields.

开发了小圆形电子场的经验模型。这对小圆形电子场的治疗计划过程有很大帮​​助。使用 3D 水模型和针点离子室对 6 MeV 和 20 MeV 之间的标称电子能量进行了由电子切口直径 (2 cm–9 cm) 定义的圆形场的完整剂量分析。研究的特性包括深度剂量、空中平方反比衰减和光束轮廓。使用 EGSnrc/BEAMnrc 代码对 Varian Clianc 2100 C 加速器进行建模、基准测试和蒙特卡罗模拟，用于小圆形切口。发现一个简单的指数模型可以准确地预测非常重要的治疗深度（Dmax 的 90%），在大多数情况下精度优于 2 mm。₉₀和“b”）。此外，研究了这些小圆形电子场的半影宽度（离轴轮廓的 90%），并将最小二乘拟合到一个简单的二次模型。使用基准蒙特卡罗模拟进一步研究了这些小圆形电子场的完整剂量分布。这项研究提出了一个简单的模型来预测非常重要的治疗深度（Dmax 的 90%），以及为任何直线加速器系统开发这种电子治疗模型的方法。在治疗计划之前，这种预测可能非常有价值并且可以节省时间，不仅涉及小的圆形电子场，还涉及不规则形状的电子场。