摘要
目的:分析研究具有非均整(FFF)模式的医用直线加速器机房放射防护设计与屏蔽效果,为医用直线加速器FFF模式的放射防护设计提供技术参考。方法:在Versa HD型医用直线加速器X射线能量10 MV、照射野40 cm×40 cm条件下,分别使用均整模式最大输出剂量率600 MU/min和FFF模式最大输出剂量率2200 MU/min照射,按照国家职业卫生标准(GBZ126-2011)规定的方法,对加速器机房外表面30 cm处剂量水平进行检测,对检测结果中的超标位点计算改造方案的屏蔽厚度,并在改造完成后重新进行检测。结果:按照均整模式设计的原屏蔽方案在10 MV的FFF模式下,机房外表面部分检测点辐射剂量率>2.5μSv/h,超出国家职业卫生标准(GBZ126-2011)限值(≤2.5μSv/h)要求;防护门外中子辐射剂量当量率最大为1.0μSv/h,明显高于预期值。根据检测结果计算需要增加的屏蔽厚度,改造完成后原超标位点辐射剂量率均<2.5μSv/h,满足标准限值要求。结论:在FFF模式下机房外表面辐射剂量率较均整模式明显增加,具备10 MV的FFF模式的医用直线加速器机房设计需要考虑中子防护,在不改变周围剂量当量率参考控制水平的情况下,需要增加屏蔽厚度才能达到国家标准要求。
Objective:To analyze the effects of design and radiation shielding of machine room of medical linear accelerator with flattening filter free(FFF)mode,so as to provide a technique reference for the design of radiation shielding of FFF mode of linear accelerator.Methods:Under the conditions of X-ray energy with 10MV and radiation field with 40 cm×40 cm of Versa HD medical linear accelerator,the maximum output dosage rate(600MU/min)of flattening filter mode and that(2200MU/min)of FFF mode were respectively used to implement radiation.According to the method of National Occupational Health Standard(GBZ126-2011),the dosage levels at the 30cm away the outside surface of machine room was detected.The thickness of radiation shielding of modification scheme of the point which exceeded the standard in the detection results was calculated,and the detection was implemented again after the modification was completed.Results:Under the FFF mode with 10MV,the original shielding scheme were designed as FF mode.The radiation dose rate of the part of detecting points outside the surface of machine room was larger than 2.5μSv/h,which exceeded the limiting value(≤2.5μSv/h)of National Occupational Health Standard(GBZ126-2011).And the maximum value of neutron radiation dose equivalent rate outside the door was 1.0μSv/h,which was significantly higher than expected value.And the thickness of radiation shielding that should be added was calculated according to the detection results.All of radiation dose rates of the points of original scheme that exceeded the standard were less than 2.5μSv/h after the scheme was modified,which could meet the requirement of the limiting value of standard.Conclusion:The radiation dose rate of outside surface of machine room under FFF mode was significantly higher than that of FF mode.The design of the machine room of medical linear accelerator which has FFF mode with 10 MV should consider to shield neutron.And we should add the thickness of radiation shielding to achieve the requirement of national s
作者
董硕
张文龙
白玫
殷旭君
张秋杭
徐建堃
吴航
DONG Shuo;ZHANG Wen-long;BAI Mei(Department of Medical Engineering,Xuanwu Hospital,Capital Medical University,Beijing 100053,China;不详)
出处
《中国医学装备》
2021年第10期36-40,共5页
China Medical Equipment
基金
国家标准化管理委员会第七批社会管理和公共服务综合标准化试点项目(国标委发[2021]5号)“北京宣武医院精准放射治疗服务标准化试点”。
关键词
医用直线加速器
非均整(FFF)模式
辐射剂量率
放射治疗机房
放射防护
Medical linear accelerator
Flattening filter free(FFF)mode
Radiation dose rate
Machine room of radiotherapy
Radiation shielding
