放疗机房设计和防护检测中特殊问题的研究

目的 针对顶层薄弱的放疗机房,对机房周围的天空反射和侧向散射光子辐射进行计算和检测,探讨计算和检测中应注意的问题。方法 依据NCRP第151号报告中给出的计算方法及公式,对两个顶层薄弱的医用直线加速器机房周围天空反射和侧向散射光子辐射进行计算,并对机房周围地面和临近高层建筑的辐射水平进行检测,将计算结果和检测结果进行对比。结果 天空反射的计算结果和检测结果存在一定差异,侧向散射光子辐射计算结果与测量结果处于同一数量级水平。结论 对顶层薄弱的放疗机房,应考虑天空反射和侧向散射光子辐射,NCRP第151号报告中给出的天空反射理论计算公式存在局限性。

Special Considerations about Designing and Protection Measurements of Radiotherapy Facilities

Objective Some radiation facilities are designed with little shielding in the ceiling above the accelerator. This paper is to calculate and mesure skyshine and side-scattered for these accelerator facilities, and to study the caution required for the calculation and measurement. Methods The examples are based on two medical linear accelerator room with little shielding in the ceiling. To compare skyshine and side-scattered measurements with values calculated using the techniques presented in NCRP Report No. 151. Results There is difference between the calculated and measured values of skyshine. It gets an rough order of magnitude between the calculation and measurement of side-scattered. Conclusion For radiation therapy rooms with thin roof barriers, we should consider skyshine and side-scattered. The calculation equation of skyshine given by NCRP Report No. 151 exists limitation.