ProBeam质子治疗系统辐射屏蔽的防护效果

Effectiveness of radiation shielding design for ProBeam proton therapy system

目的:对医用质子治疗系统的辐射屏蔽效果进行实际测量和分析,以期为相关单位和部门进行质子放射工作场所辐射防护检测或相关研究提供参考。方法:以瓦里安ProBeam质子治疗系统为研究对象,根据回旋加速器、治疗机房的布局和质子束流的传输路径和方向,进行了各关注点位的布局设计。另外,测量方案中对各关注点位设计了最不利工况,使用X/γ探测器和中子探测器对各关注点位在对应工况下的X/γ剂量率和中子剂量率进行实测,并对测量结果进行理论分析。结果:各关注点位实测到的X/γ和中子剂量率均低于辐射防护标准要求的限值,且大部分点位的实测数据接近环境本底水平。其中,位于降能器上方电源室的U1点位的剂量率测量值最高,为2.28μSv/h,同样低于防护标准要求的适用于该点位的剂量率限值10μSv/h。结论:本研究涉及的质子治疗系统的屏蔽设计满足辐射防护的要求,所有关注点位在最不利条件下的剂量率实测结果均满足防护标准的剂量率限值要求。对于质子治疗系统屏蔽防护效果研究的点位布局及测量工况设计和实测数据方面,本工作可以为同类研究提供参考依据。

Objective To measure and analyze the effectiveness of radiation shielding design for medical proton therapy system for providing a reference for relevant institutes and departments to carry out radiation protection measurements in proton radiation workplace and related researches.Methods Taking Varian ProBeam proton therapy system as the research object,a number of concerned measurement positions were selected according to the layouts of the cyclotron,treatment rooms and proton beam transmission path.Furthermore,the worst-case scenarios were chosen at each concerned position during the measurements.X/γdetectors and neutron detectors were used to measure the ambient radiation levels(X/γdose rate and neutron dose rate)at each concerned position in different case scenarios of the proton system,and a theoretical analysis was carried out on the measurement results.Results The dose rates of X/γand neutron at each concerned position were all below the limit of radiation protection standard,and most of the measurements were close to the background level.Particularly,the maximal dose rate which measured at the U1 position in the power room upon the energy degrader was 2.28μSv/h,lower than the dose rate limit(10μSv/h)applicable to this point that was required by the radiation protection standard.Conclusion The radiation shielding design for proton therapy system meets the requirements of radiation protection standard.All the measured dose rates at concerned positions in worst-case scenarios are within the tolerance of radiation protection standard.The idea of concerned position selection,setting up the worst-case scenarios and onsite radiation measurement in this research provides a reference for similar researches.