| 张达光,朱紫夕,孙佳娜,田源,王伟.低能X射线术中放射治疗的辐射屏蔽[J].中华放射医学与防护杂志,2022,42(8):629-635 |
| 低能X射线术中放射治疗的辐射屏蔽 |
| Radiation shielding for the intraoperative radiotherapy using low energy X-rays |
| 投稿时间：2022-03-16 |
| DOI：10.3760/cma.j.cn112271-20220316-00103 |
| 中文关键词: 术中放射治疗 低能X射线治疗机 放射防护 屏蔽设计 |
| 英文关键词:Intraoperative radiotherapy Low energy X-ray radiotherapy unit Radiation protection Shielding design |
| 基金项目:国家自然科学基金（81872472）；MDAnderson癌症中心全球学术项目（4-1-97） |
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| 中文摘要: |
| 目的 依据国内外标准和指南评估低能X射线术中放射治疗室的屏蔽需求，测量屏蔽材料的透射系数、关注位置的周围剂量当量率水平以及防护装置的应用效果，为此类设备屏蔽方案的设计和防护装置的应用提供参考。方法 分别依据我国GBZ 121标准、英国医学物理与工程研究所（IPEM）75号报告和美国国家辐射防护与测量委员会（NCRP）151号报告计算INTRABEAM术中放射治疗室所需的屏蔽厚度。实际测量固体水板、屏蔽贴片和防辐射围裙对于此设备产生低能X射线的透射系数，对模拟治疗条件下关注位置处的周围剂量当量率进行测量并评估辐射防护屏的应用效果。结果 依据不同标准和指南计算得到治疗室全部关注点处所需铅屏蔽厚度均<0.6 mm，差异为亚毫米水平。此设备产生的低能X射线在屏蔽物质中衰减明显，0.05 mm铅当量屏蔽贴片和0.25 mm铅当量防辐射围裙的透射系数为0.068和0.0038。使用球形施用器在空气中进行照射时，距离射线源1和2 m处测得的周围剂量当量率为10.7和2.6 mSv/h。将施用器置于小水箱中后，相应的周围剂量当量率降为3.8和0.9 μSv/h，防护屏的使用可以使2 m处的周围剂量当量率降为本底水平。结论 低能X射线术中放射治疗设施的屏蔽需求较低，设备产生的射线有效能量低，但在邻近未屏蔽辐射源位置的剂量率较高，应优化设计治疗室屏蔽方案并合理使用防护装置。 |
| 英文摘要: |
| Objective To assess the shielding requirements of low energy X-ray intraoperative radiotherapy room under the domestic and foreign standards and guidelines, to measure the sured transmission factors for a range of shielding materials, the ambient dose equivalent rate around concerned positions and the shielding effect of protective devices, so as to provide references for shielding design of such radiotherapy units and applications of radiological protection devices.Methods The required shielding thicknesses for a treatment room with INTRABEAM intraoperative radiotherapy system were calculated under the Chinese national standard GBZ 121, IPEM report No. 75 and NCRP report No. 151, respectively. The transmission factors for a range of shielding materials including solid water slab, shielding sheet and shielding apron were measured. Moreover, the ambient dose equivalent rates were measured under the simulated working conditions and the shielding effectiveness of a lead screen was evaluated.Results The required lead thicknesses calculated under different standards and guidelines were less than 0.6 mm for all the concerned points, with the differences at sub-millimeter level. The low energy X-rays generated by this equipment attenuated rapidly in the shielding materials. The measured transmission factors of 0.05 mm lead equivalent shielding sheet and 0.25 mm lead equivalent shielding apron were 0.068 and 0.0038, respectively. When the radiation was delivered using spherical applicator without any attenuation, the ambient dose equivalent rates at 1 m and 2 m from the X-ray source were 10.7 and 2.6 mSv/h, respectively. The corresponding measurement values decreased to 3.8 and 0.9 μSv/h, respectively, when the spherical applicator was inserted into a small water tank. Meanwhile, the ambient dose equivalent rate at 2 m was reduced to the background level when using protective screen.Conclusions The shielding requirements for a low energy X-ray intraoperative radiotherapy facility are minimal, with low effective energy of X-rays generated by this equipment, but the dose rate close to the unshielded radiation source is high. The shielding scheme of treatment room should be optimized in design and the protective device should be used in a reasonable way. |
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