Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA 19111, USA. Department of Physics, Faculty of Science, AlAzhar University, Nasr City, Cairo, Egypt.
Phys Med Biol. 2014 Feb 21;59(4):819-36. doi: 10.1088/0031-9155/59/4/819. Epub 2014 Feb 3.
Electron beam therapy has been an important radiation therapy modality for many decades. Studies have been conducted recently for more efficient and advanced delivery of electron beam radiation therapy. X-ray contamination is a common problem that exists with all of the advanced electron beam therapy techniques such as Bolus Electron conformal therapy, segmented electron conformal therapy, and modulated electron arc therapy. X-ray contamination could add some limitations to the advancement and clinical utility of those electron modalities. It was previously shown in the literature that the scattering foil is one of the major accelerator parts contributing to the generation of bremsstrahlung photons. Thus, in this work we investigate the dosimetric characteristics of scattering foil free (SFF) electron beams and the feasibility of using those beams for breast cancer boosts. The SFF electron beams were modeled and simulated using the Monte Carlo method. CT scans of six previously treated breast patients were used for the treatment plan generation utilizing our in-house Monte Carlo-based treatment planning system. Electron boost plans with conventional beams and the SFF beams were generated, respectively, for all patients. A significant reduction of the photon component was observed with the removal of the primary scattering foil for beam energies higher than 12 MeV. Flatness was greatly affected but the difference in flatness between conventional and SFF beams was much reduced for small cone sizes, which were often used clinically for breast boosts. It was found that the SFF electron beams could deliver high-quality dose distributions as conventional electron beams for boost treatments of the breast with an added advantage of a further reduced dose to the lung and the heart.
电子束治疗在过去几十年一直是一种重要的放射治疗方式。最近已经开展了研究，以更有效地提供电子束放射治疗。X 射线污染是所有先进的电子束治疗技术都存在的一个常见问题，如电子束适形调强治疗、电子束分段适形调强治疗和调制电子弧形治疗。X 射线污染可能会给这些电子模式的发展和临床应用带来一些限制。文献之前已经表明，散射箔是产生韧致辐射光子的主要加速器部件之一。因此，在这项工作中，我们研究了无散射箔（SFF）电子束的剂量学特性，以及使用这些束进行乳腺癌增强治疗的可行性。使用蒙特卡罗方法对 SFF 电子束进行了建模和模拟。使用我们内部基于蒙特卡罗的治疗计划系统，对六名以前接受过治疗的乳腺癌患者的 CT 扫描进行了治疗计划生成。分别为所有患者生成了使用常规束和 SFF 束的电子增强计划。对于高于 12 MeV 的束能，去除初级散射箔后，观察到光子分量显著减少。平坦度受到很大影响，但对于小锥角，常规束和 SFF 束之间的平坦度差异大大减小，小锥角常用于临床的乳腺癌增强治疗。研究发现，SFF 电子束可以像常规电子束一样为乳腺癌的增强治疗提供高质量的剂量分布，同时还可以进一步降低对肺和心脏的剂量。
