{"title":"放射治疗拱顶中与内部铅板相关的不合规中子剂量","authors":"Eduardo Galiano, Camila Salata, Marcelo Godin","doi":"10.1002/acm2.70182","DOIUrl":null,"url":null,"abstract":"<div>\n \n \n <section>\n \n <h3> Background</h3>\n \n <p>In high energy radiotherapy treatment vaults, photoneutrons can be produced by direct photon interactions with barrier materials and have a mean energy of approximately 20% of the nominal photon energy. Excess photoneutrons outside a treatment vault are always a concern due to their significant radiobiological efficacy, or Q value.</p>\n </section>\n \n <section>\n \n <h3> Methods</h3>\n \n <p>A pre-clinical regulatory inspection of a newly installed linear accelerator detected legally non-compliant photoneutron dose levels in a controlled area outside the treatment vault. The non-compliant dose was measured for a 10 MV photon beam external to the primary barrier improperly containing an internal 2.0 cm lead slab.</p>\n </section>\n \n <section>\n \n <h3> Results</h3>\n \n <p>Based on measurements at a photon energy of 10 MV, using a workload <i>W</i> = 1500 Gy/week, a use factor of <i>U</i> = 1, and an occupancy factor of <i>T </i>= 0.5—which are NCRP-151 recommended values—an equivalent neutron weekly dose of 443 ± 38 µSv was calculated for a point in a controlled area external to the vault (point A in Figure 1). This results in a calculated annual neutron dose at this point of 22.1 ± 2.2 mSv, which exceeds the legal occupational annual limit of 20 mSv for a controlled area in our jurisdiction. The lead slab was removed. Neutron measurements taken subsequent to the removal of the slab detected values slightly above natural background.</p>\n </section>\n \n <section>\n \n <h3> Conclusions</h3>\n \n <p>The probable source of the non-compliant neutron dose outside the treatment vault was the presence of the lead slab.</p>\n </section>\n </div>","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"26 8","pages":""},"PeriodicalIF":2.0000,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/acm2.70182","citationCount":"0","resultStr":"{\"title\":\"Non-compliant neutron dose associated with an internal lead slab in a radiotherapy treatment vault\",\"authors\":\"Eduardo Galiano, Camila Salata, Marcelo Godin\",\"doi\":\"10.1002/acm2.70182\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div>\\n \\n \\n <section>\\n \\n <h3> Background</h3>\\n \\n <p>In high energy radiotherapy treatment vaults, photoneutrons can be produced by direct photon interactions with barrier materials and have a mean energy of approximately 20% of the nominal photon energy. Excess photoneutrons outside a treatment vault are always a concern due to their significant radiobiological efficacy, or Q value.</p>\\n </section>\\n \\n <section>\\n \\n <h3> Methods</h3>\\n \\n <p>A pre-clinical regulatory inspection of a newly installed linear accelerator detected legally non-compliant photoneutron dose levels in a controlled area outside the treatment vault. The non-compliant dose was measured for a 10 MV photon beam external to the primary barrier improperly containing an internal 2.0 cm lead slab.</p>\\n </section>\\n \\n <section>\\n \\n <h3> Results</h3>\\n \\n <p>Based on measurements at a photon energy of 10 MV, using a workload <i>W</i> = 1500 Gy/week, a use factor of <i>U</i> = 1, and an occupancy factor of <i>T </i>= 0.5—which are NCRP-151 recommended values—an equivalent neutron weekly dose of 443 ± 38 µSv was calculated for a point in a controlled area external to the vault (point A in Figure 1). This results in a calculated annual neutron dose at this point of 22.1 ± 2.2 mSv, which exceeds the legal occupational annual limit of 20 mSv for a controlled area in our jurisdiction. The lead slab was removed. Neutron measurements taken subsequent to the removal of the slab detected values slightly above natural background.</p>\\n </section>\\n \\n <section>\\n \\n <h3> Conclusions</h3>\\n \\n <p>The probable source of the non-compliant neutron dose outside the treatment vault was the presence of the lead slab.</p>\\n </section>\\n </div>\",\"PeriodicalId\":14989,\"journal\":{\"name\":\"Journal of Applied Clinical Medical Physics\",\"volume\":\"26 8\",\"pages\":\"\"},\"PeriodicalIF\":2.0000,\"publicationDate\":\"2025-07-26\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://onlinelibrary.wiley.com/doi/epdf/10.1002/acm2.70182\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Applied Clinical Medical Physics\",\"FirstCategoryId\":\"3\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1002/acm2.70182\",\"RegionNum\":4,\"RegionCategory\":\"医学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Applied Clinical Medical Physics","FirstCategoryId":"3","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/acm2.70182","RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING","Score":null,"Total":0}
Non-compliant neutron dose associated with an internal lead slab in a radiotherapy treatment vault
Background
In high energy radiotherapy treatment vaults, photoneutrons can be produced by direct photon interactions with barrier materials and have a mean energy of approximately 20% of the nominal photon energy. Excess photoneutrons outside a treatment vault are always a concern due to their significant radiobiological efficacy, or Q value.
Methods
A pre-clinical regulatory inspection of a newly installed linear accelerator detected legally non-compliant photoneutron dose levels in a controlled area outside the treatment vault. The non-compliant dose was measured for a 10 MV photon beam external to the primary barrier improperly containing an internal 2.0 cm lead slab.
Results
Based on measurements at a photon energy of 10 MV, using a workload W = 1500 Gy/week, a use factor of U = 1, and an occupancy factor of T = 0.5—which are NCRP-151 recommended values—an equivalent neutron weekly dose of 443 ± 38 µSv was calculated for a point in a controlled area external to the vault (point A in Figure 1). This results in a calculated annual neutron dose at this point of 22.1 ± 2.2 mSv, which exceeds the legal occupational annual limit of 20 mSv for a controlled area in our jurisdiction. The lead slab was removed. Neutron measurements taken subsequent to the removal of the slab detected values slightly above natural background.
Conclusions
The probable source of the non-compliant neutron dose outside the treatment vault was the presence of the lead slab.
期刊介绍：
Journal of Applied Clinical Medical Physics is an international Open Access publication dedicated to clinical medical physics. JACMP welcomes original contributions dealing with all aspects of medical physics from scientists working in the clinical medical physics around the world. JACMP accepts only online submission.
JACMP will publish:
-Original Contributions: Peer-reviewed, investigations that represent new and significant contributions to the field. Recommended word count: up to 7500.
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