Medical Physics Division, Dr. Kamakshi Memorial Hospital, No. 1, Radial Road, Pallikaranai, Chennai - 600 100, Tamil Nadu, India.
Technol Cancer Res Treat. 2013 Jun;12(3):207-16. doi: 10.7785/tcrt.2012.500316. Epub 2013 Jan 25.
The 4 MV photon beam offers equal build-up region behavior like Co-60 beam and it plays a major role in head and neck and pediatric radiotherapy. In this study an attempt is made to study the head scatter factor (SC) for 4 MV photon beam using locally designed PMMA and Brass miniphantoms. The SC is measured in combination of PMMA miniphantom with 0.6 cc chamber and Brass miniphantom with 0.6 cc and 0.13 cc chambers. The measured SC is compared with the literature data and it agrees within ± 1.98%. The study reveals that either 0.13 cc or 0.6 cc chamber with PMMA or Brass phantom materials can be used for SC measurements in a 4 MV photon beam. The variation of SSD does not alter the head scatter factor. The collimator exchange effect is found to be within 1, and it is less than that of other linear accelerators. It is also found that the presence of internal wedge has significant contribution to head scatter factor. The Phantom scatter factor is also calculated and it agrees within ±1% with published data.
4MV 光子束具有与 Co-60 束相同的建成区行为，它在头颈部和儿科放疗中起着重要作用。本研究旨在使用本地设计的 PMMA 和 Brass 微型体模研究 4MV 光子束的头部散射因子（SC）。SC 是在 PMMA 微型体模与 0.6cc 腔室以及 Brass 微型体模与 0.6cc 和 0.13cc 腔室组合下进行测量的。测量的 SC 与文献数据进行比较，两者在 ±1.98%以内一致。该研究表明，在 4MV 光子束中，PMMA 或 Brass 体模材料的 0.13cc 或 0.6cc 腔室可用于 SC 测量。SSD 的变化不会改变头部散射因子。发现准直器交换效应在 1 以内，小于其他线性加速器。还发现内部楔形物的存在对头部散射因子有显著贡献。还计算了 Phantom 散射因子，与已发表的数据在±1%以内一致。
