Department of Radiation Oncology, Ruby Hall Clinic, Pune, India.
J Appl Clin Med Phys. 2012 Jul 5;13(4):3912. doi: 10.1120/jacmp.v13i4.3912.
In static intensity-modulated radiation therapy (IMRT), the fundamental factors that determine the quality of a plan are the number of beams and their angles. The objective of this study is to investigate the effect of beam angle optimization (BAO) on the beam number in IMRT. We used six head and neck cases to carry out the study. Basically the methodology uses a parameter called "Beam Intensity Profile Perturbation Score" (BIPPS) to determine the suitable beam angles in IMRT. We used two set of plans in which one set contains plans with equispaced beam configuration starting from beam numbers 3 to 18, and another set contains plans with optimal beam angles chosen using the in-house BAO algorithm. We used quadratic dose-based single criteria objective function as a measure of the quality of a plan. The objective function scores obtained for equispaced beam plans and optimal beam angle plans for six head and neck cases were plotted against the beam numbers in a single graphical plot for effective comparison. It is observed that the optimization of beam angles reduces the beam numbers required to produce clini-cally acceptable dose distribution in IMRT of head and neck tumors. Especially N0.1 (represents the beam number at which the objective function reaches a value of 0.1) is considerably reduced by beam angle optimization in almost all the cases included in the study. We believe that the experimental findings of this study will be helpful in understanding the interplay between beam angle optimization and beam number selection process in IMRT which, in turn, can be used to improve the performance of BAO algorithms and beam number selection process in IMRT.
在静态强度调制放射治疗（IMRT）中，决定计划质量的基本因素是射束的数量和角度。本研究的目的是研究射束角度优化（BAO）对 IMRT 中射束数量的影响。我们使用了六个头颈部病例进行了这项研究。基本上，该方法使用了一个名为“射束强度分布扰动量评分”（BIPPS）的参数来确定 IMRT 中的合适射束角度。我们使用了两组计划，一组包含从射束数 3 到 18 的等距射束配置的计划，另一组包含使用内部 BAO 算法选择的最佳射束角度的计划。我们使用基于二次剂量的单一标准目标函数作为计划质量的度量。对头颈部六个病例的等距射束计划和最佳射束角度计划获得的目标函数得分，在单个图形中绘制了射束数量的关系图，以便进行有效比较。观察到，优化射束角度可以减少在头颈部肿瘤的 IMRT 中产生临床可接受的剂量分布所需的射束数量。特别是在几乎所有纳入研究的病例中，通过射束角度优化，N0.1（表示目标函数达到 0.1 值的射束数量）明显减少。我们相信，这项研究的实验结果将有助于理解 BAO 算法和 IMRT 中射束数量选择过程之间的相互作用，从而可以提高 BAO 算法和 IMRT 中射束数量选择过程的性能。
