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The quantification and potential impact of dark current on treatments with an MR‐guided radiotherapy (MRgRT) system
PURPOSE: Dark current radiation produced during linac beam‐hold has the potential to lead to unplanned dose delivered to the patient. With the increased usage of motion management and step‐and‐shoot IMRT deliveries for MR‐guided systems leading to increased beam‐hold time, it is necessary to conside...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2020
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7769391/ https://www.ncbi.nlm.nih.gov/pubmed/33119933 http://dx.doi.org/10.1002/acm2.13059 |
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author | Shepard, Andrew J. Mittauer, Kathryn E. Bayouth, John E. Yadav, Poonam |
author_facet | Shepard, Andrew J. Mittauer, Kathryn E. Bayouth, John E. Yadav, Poonam |
author_sort | Shepard, Andrew J. |
collection | PubMed |
description | PURPOSE: Dark current radiation produced during linac beam‐hold has the potential to lead to unplanned dose delivered to the patient. With the increased usage of motion management and step‐and‐shoot IMRT deliveries for MR‐guided systems leading to increased beam‐hold time, it is necessary to consider the impact of dark current radiation on patient treatments. METHODS: The relative dose rate due to dark current for the ViewRay MRIdian linac was measured longitudinally over 15 months (June 2018‐August 2019). Ion chamber measurements were acquired with the linac in the beam‐hold state and the beam‐on state, with the ratio representing the relative dark current dose rate. The potential contribution of the dark current dose to the overall prescription was retrospectively analyzed for 972 fractions from 83 patients over the same time period. The amount of time spent in the beam‐hold state was combined with the monthly measured relative dark current dose rate to estimate the dark current dose contribution. RESULTS: The relative dark current dose rate compared to the beam‐on dose rate was 0.12% ± 0.027%. In a near worst‐case estimation, the dark current dose contribution accounted for 0.90% ± 0.67% of the prescription dose across all fractions (3.61% maximum). Gantry and MLC motion between segments accounted for 87% of the dark current contribution, with the remaining 13% attributable to gating during segment delivery. The largest dark current contributions were associated with plans delivering a small dose per treatment segment. CONCLUSIONS: The dark current associated with new clinical treatment units should be considered prior to treatment delivery to ensure it will not lead to dosimetric inaccuracies. For the MRIdian linac system investigated in this work, the contribution from dark current remained relatively low, though users should be cognizant of the larger potential dosimetric contribution for plans with small doses per segment. |
format | Online Article Text |
id | pubmed-7769391 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-77693912020-12-31 The quantification and potential impact of dark current on treatments with an MR‐guided radiotherapy (MRgRT) system Shepard, Andrew J. Mittauer, Kathryn E. Bayouth, John E. Yadav, Poonam J Appl Clin Med Phys Radiation Oncology Physics PURPOSE: Dark current radiation produced during linac beam‐hold has the potential to lead to unplanned dose delivered to the patient. With the increased usage of motion management and step‐and‐shoot IMRT deliveries for MR‐guided systems leading to increased beam‐hold time, it is necessary to consider the impact of dark current radiation on patient treatments. METHODS: The relative dose rate due to dark current for the ViewRay MRIdian linac was measured longitudinally over 15 months (June 2018‐August 2019). Ion chamber measurements were acquired with the linac in the beam‐hold state and the beam‐on state, with the ratio representing the relative dark current dose rate. The potential contribution of the dark current dose to the overall prescription was retrospectively analyzed for 972 fractions from 83 patients over the same time period. The amount of time spent in the beam‐hold state was combined with the monthly measured relative dark current dose rate to estimate the dark current dose contribution. RESULTS: The relative dark current dose rate compared to the beam‐on dose rate was 0.12% ± 0.027%. In a near worst‐case estimation, the dark current dose contribution accounted for 0.90% ± 0.67% of the prescription dose across all fractions (3.61% maximum). Gantry and MLC motion between segments accounted for 87% of the dark current contribution, with the remaining 13% attributable to gating during segment delivery. The largest dark current contributions were associated with plans delivering a small dose per treatment segment. CONCLUSIONS: The dark current associated with new clinical treatment units should be considered prior to treatment delivery to ensure it will not lead to dosimetric inaccuracies. For the MRIdian linac system investigated in this work, the contribution from dark current remained relatively low, though users should be cognizant of the larger potential dosimetric contribution for plans with small doses per segment. John Wiley and Sons Inc. 2020-10-29 /pmc/articles/PMC7769391/ /pubmed/33119933 http://dx.doi.org/10.1002/acm2.13059 Text en © 2020 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Radiation Oncology Physics Shepard, Andrew J. Mittauer, Kathryn E. Bayouth, John E. Yadav, Poonam The quantification and potential impact of dark current on treatments with an MR‐guided radiotherapy (MRgRT) system |
title | The quantification and potential impact of dark current on treatments with an MR‐guided radiotherapy (MRgRT) system |
title_full | The quantification and potential impact of dark current on treatments with an MR‐guided radiotherapy (MRgRT) system |
title_fullStr | The quantification and potential impact of dark current on treatments with an MR‐guided radiotherapy (MRgRT) system |
title_full_unstemmed | The quantification and potential impact of dark current on treatments with an MR‐guided radiotherapy (MRgRT) system |
title_short | The quantification and potential impact of dark current on treatments with an MR‐guided radiotherapy (MRgRT) system |
title_sort | quantification and potential impact of dark current on treatments with an mr‐guided radiotherapy (mrgrt) system |
topic | Radiation Oncology Physics |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7769391/ https://www.ncbi.nlm.nih.gov/pubmed/33119933 http://dx.doi.org/10.1002/acm2.13059 |
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