Khosravi Mostafa, Shahbazi-Gahrouei Daryoush, Jabbari Keyvan, Nasri-Nasrabadi Mehdi, Baradaran-Ghahfarokhi Milad, Siavashpour Zahra, Gheisari Ruhollah, Amiri Behnam
Department of Medical Physics and Medical Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.
Radiat Prot Dosimetry. 2013 Sep;156(3):356-63. doi: 10.1093/rpd/nct078. Epub 2013 Mar 28.
Dose escalation with high-energy X rays of medical linear accelerators (linacs) in radiotherapy offers several distinct advantages over the lower energy photons. However, owing to photoneutron reactions, interaction of high-energy photons (>8 MV) with various high-Z nuclei of the materials in the linac head components produces unavoidable neutrons. The aim of this study was to evaluate the photoneutron dose equivalent per unit therapeutic X-ray dose of 18 MV, GE Saturne 20 linac in the treatment room using Monte Carlo (MC) MCNP linac head full simulation as well as thermoluminescence dosemeter measurements. This machine is one of the old linac models manufactured by General Electric Company; however, it is widely used in the developing countries because of low cost and simple maintenance for radiotherapy applications. The results showed a significant photoneutron dose from Saturne 20 linac head components especially at distances near the linac head (<150 cm). Results of this work could be used in several applications, especially designing bunker and entrance door shielding against neutrons produced by photoneutron reactions in GE Saturne 20. However, a detailed cost optimisation for a specific room would require a dedicated calculation.
在放射治疗中，医用直线加速器（直线加速器）使用高能X射线进行剂量递增比使用低能光子具有几个明显的优势。然而，由于光中子反应，高能光子（>8 MV）与直线加速器头部组件中材料的各种高Z原子核相互作用会产生不可避免的中子。本研究的目的是使用蒙特卡罗（MC）MCNP直线加速器头部全模拟以及热释光剂量计测量，评估治疗室中18 MV的GE Saturne 20直线加速器每单位治疗X射线剂量的光中子剂量当量。这台机器是通用电气公司制造的旧直线加速器型号之一；然而，由于成本低且放疗应用维护简单，它在发展中国家被广泛使用。结果表明，Saturne 20直线加速器头部组件产生了显著的光中子剂量，尤其是在直线加速器头部附近的距离（<150 cm）处。这项工作的结果可用于多种应用，特别是设计针对GE Saturne 20中光中子反应产生的中子的掩体和入口门屏蔽。然而，针对特定房间的详细成本优化需要进行专门的计算。
