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Evaluation of a conventionally shielded proton treatment room for FLASH radiotherapy

PURPOSE: FLASH radiotherapy (FLASH‐RT) is the potential for a major breakthrough in cancer care, as preclinical results have shown significantly reduced toxicities to healthy tissues while maintaining excellent tumor control. However, FLASH conditions were not considered in the current proton facili...

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Autores principales: Xiao, Zhiyan, Zhang, Yongbin, Speth, Joseph, Lee, Eunsin, Mascia, Anthony, Lamba, Michael
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10091931/
https://www.ncbi.nlm.nih.gov/pubmed/36114793
http://dx.doi.org/10.1002/mp.15964
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author Xiao, Zhiyan
Zhang, Yongbin
Speth, Joseph
Lee, Eunsin
Mascia, Anthony
Lamba, Michael
author_facet Xiao, Zhiyan
Zhang, Yongbin
Speth, Joseph
Lee, Eunsin
Mascia, Anthony
Lamba, Michael
author_sort Xiao, Zhiyan
collection PubMed
description PURPOSE: FLASH radiotherapy (FLASH‐RT) is the potential for a major breakthrough in cancer care, as preclinical results have shown significantly reduced toxicities to healthy tissues while maintaining excellent tumor control. However, FLASH conditions were not considered in the current proton facilities’ shielding designs. The purpose of this study is to validate the adequacy of conventionally shielded proton rooms used for FLASH‐RT. METHODS: Clinical FLASH irradiations typically take place in a few 100 ms, orders of magnitude shorter than the response time of the wide‐energy neutron detector (WENDI–II). The nozzle beam current (representing the dose rate) dependence of the WENDI–II detector response was empirically determined to stabilize with a beam current of ≤10 nA at the measurement point with the highest dose rate. A large, predefined proton transmission FLASH plan (250 MeV, 7 × 20 cm(2), 8 Gy at isocenter) was commissioned as part of a FLASH clinical trial. For purpose of this study, that field was adjusted from 250 to 244 MeV, allowing a lower beam current of 10 nA to provide reliable detector response. Radiation surveys were performed for the proton beams with/without extra beam stopper (30 × 30 × 40‐cm(3) solid water slabs) at 0°, 90°, 180°, and 270° gantry angles. RESULTS: Ambient doses were recorded at seven different locations. A 170‐nA beam current, commonly used for clinical FLASH plans, was chosen to normalize the average ambient dose rate to FLASH conditions. Assuming 200‐Gy/h workload (25 FLASH beams, 8 Gy/beam), annual occupational dose at controlled areas was calculated. For all gantry angles, ≤0.4 mSv/year is expected at treatment room door. The highest ambient dose, 2.46 mSv/year, ∼5% of the maximum annual permissible occupational dose, was identified at the isocenter of the adjacent treatment room with 90° gantry. CONCLUSION: These survey results indicate that our conventionally shielded proton rotating gantry rooms result in acceptable occupational and public doses when the transmission FLASH beams delivered at four cardinal gantry angles based on 200‐Gy/h workload assumption. These findings support that FLASH clinical trials in our conventionally shielded proton facilities can be safely implemented.
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spelling pubmed-100919312023-04-13 Evaluation of a conventionally shielded proton treatment room for FLASH radiotherapy Xiao, Zhiyan Zhang, Yongbin Speth, Joseph Lee, Eunsin Mascia, Anthony Lamba, Michael Med Phys THERAPEUTIC INTERVENTIONS PURPOSE: FLASH radiotherapy (FLASH‐RT) is the potential for a major breakthrough in cancer care, as preclinical results have shown significantly reduced toxicities to healthy tissues while maintaining excellent tumor control. However, FLASH conditions were not considered in the current proton facilities’ shielding designs. The purpose of this study is to validate the adequacy of conventionally shielded proton rooms used for FLASH‐RT. METHODS: Clinical FLASH irradiations typically take place in a few 100 ms, orders of magnitude shorter than the response time of the wide‐energy neutron detector (WENDI–II). The nozzle beam current (representing the dose rate) dependence of the WENDI–II detector response was empirically determined to stabilize with a beam current of ≤10 nA at the measurement point with the highest dose rate. A large, predefined proton transmission FLASH plan (250 MeV, 7 × 20 cm(2), 8 Gy at isocenter) was commissioned as part of a FLASH clinical trial. For purpose of this study, that field was adjusted from 250 to 244 MeV, allowing a lower beam current of 10 nA to provide reliable detector response. Radiation surveys were performed for the proton beams with/without extra beam stopper (30 × 30 × 40‐cm(3) solid water slabs) at 0°, 90°, 180°, and 270° gantry angles. RESULTS: Ambient doses were recorded at seven different locations. A 170‐nA beam current, commonly used for clinical FLASH plans, was chosen to normalize the average ambient dose rate to FLASH conditions. Assuming 200‐Gy/h workload (25 FLASH beams, 8 Gy/beam), annual occupational dose at controlled areas was calculated. For all gantry angles, ≤0.4 mSv/year is expected at treatment room door. The highest ambient dose, 2.46 mSv/year, ∼5% of the maximum annual permissible occupational dose, was identified at the isocenter of the adjacent treatment room with 90° gantry. CONCLUSION: These survey results indicate that our conventionally shielded proton rotating gantry rooms result in acceptable occupational and public doses when the transmission FLASH beams delivered at four cardinal gantry angles based on 200‐Gy/h workload assumption. These findings support that FLASH clinical trials in our conventionally shielded proton facilities can be safely implemented. John Wiley and Sons Inc. 2022-10-03 2022-11 /pmc/articles/PMC10091931/ /pubmed/36114793 http://dx.doi.org/10.1002/mp.15964 Text en © 2022 The Authors. Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine. https://creativecommons.org/licenses/by-nc-nd/4.0/This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ (https://creativecommons.org/licenses/by-nc-nd/4.0/) License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
spellingShingle THERAPEUTIC INTERVENTIONS
Xiao, Zhiyan
Zhang, Yongbin
Speth, Joseph
Lee, Eunsin
Mascia, Anthony
Lamba, Michael
Evaluation of a conventionally shielded proton treatment room for FLASH radiotherapy
title Evaluation of a conventionally shielded proton treatment room for FLASH radiotherapy
title_full Evaluation of a conventionally shielded proton treatment room for FLASH radiotherapy
title_fullStr Evaluation of a conventionally shielded proton treatment room for FLASH radiotherapy
title_full_unstemmed Evaluation of a conventionally shielded proton treatment room for FLASH radiotherapy
title_short Evaluation of a conventionally shielded proton treatment room for FLASH radiotherapy
title_sort evaluation of a conventionally shielded proton treatment room for flash radiotherapy
topic THERAPEUTIC INTERVENTIONS
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10091931/
https://www.ncbi.nlm.nih.gov/pubmed/36114793
http://dx.doi.org/10.1002/mp.15964
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