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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。“,”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.Methods:The 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_Dn w with relative small difference compared with that between GBZT_Dn w and GBZT_IDR.n Conclusions:The 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.