| 潘永祥,李明生,郭朝晖,程金生.重混凝土屏蔽质子放疗机房的感生放射性估算[J].中华放射医学与防护杂志,2020,40(4):321-325 |
| 重混凝土屏蔽质子放疗机房的感生放射性估算 |
| Calculation of induced radioactivity of heavy concrete shielding wall in proton therapy room |
| 投稿时间：2019-12-10 |
| DOI：10.3760/cma.j.issn.0254-5098.2020.04.013 |
| 中文关键词: 质子治疗 重混凝土 感生放射性 周围剂量当量率 |
| 英文关键词:Proton therapy Heavy concrete Induced radioactivity Ambient dose equivalent rate |
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| 中文摘要: |
| 目的 估算肿瘤质子治疗时重混凝土屏蔽墙中铁元素因中子活化产生的感生放射性56Mn及其水平。方法 采用Geant4程序构建某质子治疗机房的重混凝土屏蔽墙模型，模拟245 MeV的质子束照射水模体产生的次级中子，统计屏蔽墙内放射性核素56Mn的分布。将屏蔽墙按每10 cm厚度分层，计算前3层屏蔽墙中放射性核素56Mn产生的周围剂量当量率。结果 在最大的束流照射条件（1.872×1010个）下，前3层屏蔽墙内的放射性核素56Mn个数分别为3.10×108、1.60×108和9.33×107个；对治疗室内1 m远处产生的周围剂量当量率分别为2.13×10-3、8.82×10-4 和9.10×10-4 μSv/h，总的周围剂量当量率为3.92×10-3 μSv/h。结论 在质子治疗时，距离射束中心轴越近，屏蔽墙的感生放射性越强；屏蔽墙前端中子活化铁元素产生的感生放射性最强，感生放射性随着屏蔽墙厚度增大呈指数形式减小，应主要考虑质子治疗机房屏蔽墙前端产生的感生放射性。 |
| 英文摘要: |
| Objective To estimate the induced radioactive 56Mn and its level of iron in heavy concrete shielding wall due to neutron activation during tumor proton therapy. Methods A Geant4 program was adopted to build the model of a heavy concrete shielding wall in a proton therapy room, simulate secondary neutrons generated by 245 MeV proton beam irradiating water phantom. The statistical distribution of radionuclide 56Mn in shielding wall was calculated. The shielding wall was layered every 10 cm thickness, the dose equivalent rate of radionuclide 56Mn in the first three shielding walls was calculated. Results Under the maximum beam irradiation conditions (1.872×1010), the number of radionuclide 56Mn in the first three layers of shielding walls are 3.10×108, 1.60×108, 9.33×107. The ambient dose equivalent rate at a distance of 1 m from the treatment room are 2.13×10-3, 8.82×10-4, 9.10×10-4 μSv/h, and the total ambient dose equivalent rate for the first three layers was 3.92×10-3 μSv/h. Conclusions During proton therapy, the shielded walls near the central axis of the beam produce more induced radioactivity. The induced radioactivity produced by the neutron-activated iron element at the ahead of the shielding wall is the strongest, and decreases exponentially as the thickness of the shield wall increases.The induced radioactivity in front of the shielding wall of proton therapy room should be concerned. |
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