Giżyńska Marta Krystyna, Kukołowicz Paweł F
Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Centre and Institute of Oncology, Warsaw, Poland.
Biomedical Physics Division, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Poland.
Rep Pract Oncol Radiother. 2014 May 13;19(Suppl):S9-S12. doi: 10.1016/j.rpor.2014.03.002. eCollection 2014 May.
In this work we test the usage of dose gradient based algorithm for the selection of beam weights in 3D-CRT plans for different cancer locations. Our algorithm is easy to implement for three fields technique with wedges defined by planner.
3D-CRT is usually realized with forward planning which is quite time consuming. Several authors published a few methods of beams weights optimization applicable to the 3D-CRT.
Optimization is based on an assumption that the best plan is achieved if dose gradient at ICRU point is equal to zero. Method was tested for 120 patients, treated in our clinic in 2011-2012, with different cancer locations. For each patient, three fields conformal plan (6 MV and 15 MV X-ray) with the same geometry as proposed by experienced planners was prepared. We compared dose distributions achieved with the proposed method and those prepared by experienced planners. The homogeneity of dose distributions was compared in terms of STD and near minimum and near maximum doses in the PTV.
Mean difference of STD obtained by the proposed algorithm and by planners was 0.1%: 0.1% for prostate cancer, 0.3% for lung cancer, -0.1% for esophagus cancer, 0.1% for rectum cancer, -0.1% for gynecology cancer, -0.1% for stomach cancer.
Applying the proposed algorithm leads to obtain the similar dose distribution homogeneity in the PTV as these achieved by planners and therefore can serve as a support in creating 3D-CRT plans. It is also simple to use and can significantly speed up the treatment planning process.
在本研究中，我们测试了基于剂量梯度的算法在不同癌症部位的三维适形放疗（3D - CRT）计划中选择射束权重的应用。我们的算法对于由计划者定义楔形板的三野技术而言易于实现。
3D - CRT通常通过正向计划来实现，这相当耗时。几位作者发表了一些适用于3D - CRT的射束权重优化方法。
优化基于这样一种假设，即如果国际辐射单位与测量委员会（ICRU）点处的剂量梯度等于零，则可实现最佳计划。该方法针对2011 - 2012年在我们诊所接受治疗的120例不同癌症部位的患者进行了测试。对于每位患者，准备了具有与经验丰富的计划者所提议相同几何形状的三野适形计划（6兆伏和15兆伏X射线）。我们比较了用所提议方法获得的剂量分布与经验丰富的计划者所制定的剂量分布。在PTV中，根据标准差以及接近最小和接近最大剂量来比较剂量分布的均匀性。
所提议算法与计划者获得的标准差的平均差异为0.1%：前列腺癌为0.1%，肺癌为0.3%，食管癌为 - 0.1%，直肠癌为0.1%，妇科癌症为 - 0.1%，胃癌为 - 0.1%。
应用所提议的算法可在PTV中获得与计划者所实现的相似的剂量分布均匀性，因此可作为创建3D - CRT计划的一种辅助手段。它使用也很简单，并且可以显著加快治疗计划过程。
