放射治疗模拟机房的屏蔽改造方案设计与分析

Designing and analyzing on shielding reconstruction project of radiotherapy simulator room

目的:分析放射治疗模拟机房物理条件与设备剂量学参数的相互关系,设计并确定合理的机房屏蔽改造方案。方法:以某单位拟投入运行的1台放射治疗模拟机及其拟改造机房为研究对象,在设备调试性出束时使用451P高压电离室巡测仪和SG-102型X-γ环境剂量率仪测量机房外围关注点的辐射水平,并据此进行机房墙体的屏蔽改造方案设计。结果:该模拟机在125 kV、1.8mA的最高透视条件下,东、西主束墙外周围剂量当量率最高分别为14μSv/h和4μSv/h,机房室顶上方最高剂量率为185μSv/h,据此初步确定了该模拟机房主束屏蔽的改造方案。结论:放射治疗模拟机房外在透视条件下关注点的周围剂量当量率作为放射防护指标,根据其实测值设计机房的屏蔽改造方案实用可行。

Objective：The relationship between the physical condition of radiotherapy simulator room and dosimetry parameters of the facility was analyzed to design and determine reasonable shielding reconstruction project of the room.Methods：A normal radiotherapy simulator and its room to be reconstructed were determined as the research object.Under the condition of debugging beam-on time,a 451P high pressure ionization chamber survey meter and a SG-102 X-γ environmental dose rate meter were used to measure radiation level of the interest point in the periphery of the room.Then,the shielding reconstruction project of the simulator room was framed on the basis of the actual ambient dose equivalent rate.Results：While the simulator was beaming under the maximum fluoroscope condition of 125 kV and 1.8 mA,the maximum ambient dose equivalent rate outside east wall,west wall and roof of the room from primary radiation were 14,4 and 185μSv/h respectively.The preliminary shielding reconstruction project of the room was illustrated as：the shield thickness added on east wall.Conclusion：The ambient dose equivalent rate of interest point outside a radiotherapy simulator room can be adopted as a protective parameter,and it is practical and feasible that the shielding reconstruction project of the room is designed according to the actual measured values of radiation dose rate outside the original room.