Department of Radiation Oncology, Medical Physics Division, Advance Medicare and Research Institute Cancer Centre, Kolkata, West Bengal, India.
Br J Radiol. 2013 Nov;86(1031):20130238. doi: 10.1259/bjr.20130238. Epub 2013 Aug 30.
This report provides the mathematical commissioning instructions for the evaluation of beam matching between two different linear accelerators.
Test packages were first obtained including an open beam profile, a wedge beam profile and a depth-dose curve, each from a 10×10 cm(2) beam. From these plots, a spatial error (SE) and a percentage dose error were introduced to form new plots. These three test package curves and the associated error curves were then differentiated in space with respect to dose for a first and second derivative to determine the slope and curvature of each data set. The derivatives, also known as bandwidths, were analysed to determine the level of acceptability for the beam matching test described in this study.
The open and wedged beam profiles and depth-dose curve in the build-up region were determined to match within 1% dose error and 1-mm SE at 71.4% and 70.8% for of all points, respectively. For the depth-dose analysis specifically, beam matching was achieved for 96.8% of all points at 1%/1 mm beyond the depth of maximum dose.
To quantify the beam matching procedure in any clinic, the user needs to merely generate test packages from their reference linear accelerator. It then follows that if the bandwidths are smooth and continuous across the profile and depth, there is greater likelihood of beam matching. Differentiated spatial and percentage variation analysis is appropriate, ideal and accurate for this commissioning process.
We report a mathematically rigorous formulation for the qualitative evaluation of beam matching between linear accelerators.
本报告提供了评估两台不同直线加速器之间光束匹配的数学调试指令。
首先获得测试包，包括一个开放光束轮廓、一个楔形光束轮廓和一个深度剂量曲线，每个光束均来自 10×10cm²。从这些图中，引入了空间误差（SE）和百分比剂量误差，以形成新的图。然后，针对剂量对这三个测试包曲线和相关误差曲线进行空间微分，以确定每个数据集的斜率和曲率。这些导数，也称为带宽，用于分析以确定本文所述光束匹配测试的可接受水平。
在 71.4%和 70.8%的所有点处，开放光束和楔形光束轮廓以及在 buildup 区域的深度剂量曲线的剂量误差均在 1%以内，SE 误差均在 1mm 以内。对于深度剂量分析，在最大剂量深度以外 1%/1mm 的所有点处，实现了 96.8%的光束匹配。
为了在任何诊所量化光束匹配过程，用户只需从其参考直线加速器生成测试包。如果带宽在轮廓和深度上平滑且连续，则更有可能实现光束匹配。微分空间和百分比变化分析适用于此调试过程，是理想且准确的。
我们报告了一种用于定性评估直线加速器之间光束匹配的数学严格公式。
