Cadini Francesco, Bolst David, Guatelli Susanna, Beltran Chris, Jackson Michael, Rosenfeld Anatoly B
Politecnico di Milano, Dipartimento di Energia, Via La Masa 34, I-20156 Milano, Italy; Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia.
Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia.
Phys Med. 2016 Dec;32(12):1862-1871. doi: 10.1016/j.ejmp.2016.12.003.
In this work, we used the Monte Carlo-based Geant4 simulation toolkit to calculate the ambient dose equivalents due to the secondary neutron field produced in a new projected proton therapy facility. In particular the facility geometry was modeled in Geant4 based on the CAD design. Proton beams were originated with an energy of 250MeV in the gantry rooms with different angles with respect to the patient; a fixed 250MeV proton beam was also modeled. The ambient dose equivalent was calculated in several locations of interest inside and outside the facility, for different scenarios. The simulation results were compared qualitatively to previous work on an existing facility bearing some similarities with the design under study, showing that the ambient dose equivalent ranges obtained are reasonable. The ambient dose equivalents, calculated by means of the Geant4 simulation, were compared to the Australian regulatory limits and showed that the new facility will not pose health risks for the public or staff, with a maximum equivalent dose rate equal to 7.9mSv/y in the control rooms and maze exit areas and 1.3·10mSv/y close to the walls, outside the facility, under very conservative assumptions. This work represents the first neutron shielding verification analysis of a new projected proton therapy facility and, as such, it may serve as a new source of comparison and validation for the international community, besides confirming the viability of the project from a radioprotection point of view.
在这项工作中，我们使用基于蒙特卡罗方法的Geant4模拟工具包来计算新建质子治疗设施中产生的次级中子场导致的周围剂量当量。特别是，该设施的几何结构是基于CAD设计在Geant4中建模的。质子束在机架室中以250MeV的能量产生，相对于患者有不同的角度；还对固定的250MeV质子束进行了建模。针对不同场景，在设施内部和外部的几个感兴趣位置计算了周围剂量当量。将模拟结果与先前关于一个与正在研究的设计有一些相似之处的现有设施的工作进行了定性比较，结果表明所获得的周围剂量当量范围是合理的。通过Geant4模拟计算得到的周围剂量当量与澳大利亚的监管限值进行了比较，结果表明，在非常保守的假设下，新设施不会对公众或工作人员构成健康风险，控制室和迷宫出口区域的最大当量剂量率等于7.9mSv/y，设施外部靠近墙壁处为1.3×10mSv/y。这项工作代表了对新建质子治疗设施的首次中子屏蔽验证分析，因此，除了从辐射防护角度确认该项目的可行性外，它还可以作为国际社会新的比较和验证来源。
