中华放射医学与防护杂志

田源,宋一昕,冯泽臣,等.高能医用电子直线加速器的机房屏蔽设计方案国内外比较[J].中华放射医学与防护杂志,2020,40(12):903-910.Tian Yuan,Song Yixin,Feng Zechen,et al.Bunker shielding design scheme for high energy medical linear accelerator: Comparison between Chinese and international radiation shielding standards for radiotherapy facilities[J].Chin J Radiol Med Prot,2020,40(12):903-910

高能医用电子直线加速器的机房屏蔽设计方案国内外比较

Bunker shielding design scheme for high energy medical linear accelerator: Comparison between Chinese and international radiation shielding standards for radiotherapy facilities

投稿时间：2020-04-01

DOI：10.3760/cma.j.issn.0254-5098.2020.12.003

中文关键词: 医用直线加速器辐射防护屏蔽设计瞬时剂量当量率标准

英文关键词:Medical linear accelerator Radiation protection Shielding design Instantaneous dose-equivalent rate Standard

基金项目:

作者	单位	E-mail
田源	国家癌症中心国家肿瘤临床医学研究中心中国医学科学院北京协和医学院肿瘤医院放疗科, 北京 100021
宋一昕	国家癌症中心国家肿瘤临床医学研究中心中国医学科学院北京协和医学院肿瘤医院放疗科, 北京 100021
冯泽臣	北京市疾病预防控制中心放射卫生防护所 100013
戴建荣	国家癌症中心国家肿瘤临床医学研究中心中国医学科学院北京协和医学院肿瘤医院放疗科, 北京 100021	dai_jianrong@163.com

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中文摘要:

目的比较国内外3种标准在高能医用电子直线加速器机房屏蔽设计和效果检测中的差异，为修订和完善现行国家标准提供参考。方法对于一个具有两档X射线能量（6和10 MV），日均使用X射线治疗105例患者（90%为调强放疗技术）的高能医用电子直线加速器机房，分别按照美国国家辐射防护与测量委员会（NCRP）151号报告、英国电离辐射法规（IRR）17和GBZ/T 201现行国家标准计算并比较所需的屏蔽方案。分析按照3种标准各自评价指标计算得到的各关注点所需的混凝土屏蔽厚度随高能X射线工作负荷占比的变化。提出一种基于瞬时剂量当量率保守估计值的屏蔽效果检测和评价方法。结果按照NCRP 151号报告和IRR 17号法规计算得到的各关注点（主束次屏蔽区A、B点、主束主屏蔽区C、D点、侧墙次屏蔽点E、室顶主屏蔽点F和室顶次屏蔽点G）所需的混凝土屏蔽厚度分别为89、115、162、183、113、163、86 cm和104、130、215、213、128、207、105 cm。而GBZ/T 201屏蔽方案所需的混凝土屏蔽厚度最大，分别为136、153、243、265、131、207和105 cm。与NCRP 151号报告屏蔽方案相比，GBZ/T 201屏蔽方案治疗室内使用面积、室内层高的显著降低（分别减小14.01%和8.68%），室顶承重增加明显（24.01%）。IRR 17和GBZ/T 201屏蔽方案的最终屏蔽厚度主要由瞬时剂量当量率限值决定，基本不随高能X射线工作负荷的增加而变化。基于本文提出的瞬时剂量当量率保守估计值确定的屏蔽厚度均大于由周剂量控制目标值计算得到的屏蔽厚度，且能减小二者之间的差异。结论由于不同标准使用的评价指标（特别是剂量当量率限值）的不同，各屏蔽方案所需的屏蔽厚度差异明显。瞬时剂量当量率保守估计值作为屏蔽效果检测评价指标，安全合理且使用方便。

英文摘要:

Objective To compare the differences between Chinese and two international radiation shielding standards for radiotherapy facilities in the bunker shielding design for high energy medical linear accelerator, so as to provide reference for revising and improving the current national standard. MethodsThe required bulker shielding for a high energy (6 MV and 10 MV) medical electron linear accelerator to treat an average of 105 patients (90% with IMRT technology) per day was calculated and compared according to the NCRP report 151 (America), IRR 17 legislation (British) and Chinese national standard GBZ/T 201, respectively. The changes of the required shielding thickness of each concern point according to the change of workload were analyzed. A novel method of shielding effect evaluation based on the conservative estimation of instantaneous dose-equivalent rate was proposed. Results The values of concrete shielding thickness required for point A and B (secondary barrier of the primary wall), C and D (primary barrier of the primary wall),E(secondary barrier of the side wall),F(primary barrier of the roof) and G(secondary barrier of the roof) according to the NCRP report 151 and IRR 17 legislation were 89, 115, 162, 183, 113, 163, 86 cm, and 104, 130, 215, 213, 128, 207, 105 cm, respectively. The values for these points according to the GBZ/T 201 national standards were 136, 153, 243, 265, 131, 207 and 105 cm, respectively. Compared with the NCRP 151 shielding scheme, the indoor use area and floor height of the treatment room were significantly decreased by 14.01% and 8.68%, respectively, while the roof load-bearing increased significantly by 24.01% by GBZ/T. The final values of shielding thickness of either IRR 17 or GBZ/T 201 shielding schemes were mainly dominated by the instantaneous dose equivalent rates, generally without changing with the increase of high-energy X-ray workload. The values of shielding thickness based on the conservative estimates of instantaneous dose equivalent rate GBZT_IDR2 were larger than those calculated in terms of weekly dose control limit GBZT_D_w with relative small difference compared with that between GBZT_D_w and GBZT_IDR. ConclusionsThe differences in shielding thickness for high energy linear accelerator were obvious among different standards due to different evaluation indices, especially the dose equivalent rate limit used. The conservative estimates of instantaneous dose equivalent rate are safe, reasonable, easy to use, and available as evaluation index for shielding calculation.

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