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MOSFET dosimeter characterization in MR‐guided radiation therapy (MRgRT) Linac

PURPOSE: With the increasing use of MR‐guided radiation therapy (MRgRT), it becomes important to understand and explore accuracy of medical dosimeters in the presence of magnetic field. The purpose of this work is to characterize metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) in MRgRT...

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Autores principales: Yadav, Poonam, Hallil, Abdelbasset, Tewatia, Dinesh, Dunkerley, David A. P., Paliwal, Bhudatt
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6964768/
https://www.ncbi.nlm.nih.gov/pubmed/31854078
http://dx.doi.org/10.1002/acm2.12799
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author Yadav, Poonam
Hallil, Abdelbasset
Tewatia, Dinesh
Dunkerley, David A. P.
Paliwal, Bhudatt
author_facet Yadav, Poonam
Hallil, Abdelbasset
Tewatia, Dinesh
Dunkerley, David A. P.
Paliwal, Bhudatt
author_sort Yadav, Poonam
collection PubMed
description PURPOSE: With the increasing use of MR‐guided radiation therapy (MRgRT), it becomes important to understand and explore accuracy of medical dosimeters in the presence of magnetic field. The purpose of this work is to characterize metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) in MRgRT systems at 0.345 T magnetic field strength. METHODS: A MOSFET dosimetry system, developed by Best Medical Canada for in‐vivo patient dosimetry, was used to study various commissioning tests performed on a MRgRT system, MRIdian(®) Linac. We characterized the MOSFET dosimeter with different cable lengths by determining its calibration factor, monitor unit linearity, angular dependence, field size dependence, percentage depth dose (PDD) variation, output factor change, and intensity modulated radiation therapy quality assurance (IMRT QA) verification for several plans. MOSFET results were analyzed and compared with commissioning data and Monte Carlo calculations. RESULTS: MOSFET measurements were not found to be affected by the presence of 0.345 T magnetic field. Calibration factors were similar for different cable length dosimeters either placed at the parallel or perpendicular direction to the magnetic field, with variations of less than 2%. The detector showed good linearity (R(2) = 0.999) for 100–600 MUs range. Output factor measurements were consistent with ionization chamber data within 2.2%. MOSFET PDD measurements were found to be within 1% for 1–15 cm depth range in comparison to ionization chamber. MOSFET normalized angular response matched thermoluminescent detector (TLD) response within 5.5%. The IMRT QA verification data for the MRgRT linac showed that the percentage difference between ionization chamber and MOSFET was 0.91%, 2.05%, and 2.63%, respectively for liver, spine, and mediastinum. CONCLUSION: MOSFET dosimeters are not affected by the 0.345 T magnetic field in MRgRT system. They showed physics parameters and performance comparable to TLD and ionization chamber; thus, they constitute an alternative to TLD for real‐time in‐vivo dosimetry in MRgRT procedures.
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spelling pubmed-69647682020-01-27 MOSFET dosimeter characterization in MR‐guided radiation therapy (MRgRT) Linac Yadav, Poonam Hallil, Abdelbasset Tewatia, Dinesh Dunkerley, David A. P. Paliwal, Bhudatt J Appl Clin Med Phys Radiation Measurements PURPOSE: With the increasing use of MR‐guided radiation therapy (MRgRT), it becomes important to understand and explore accuracy of medical dosimeters in the presence of magnetic field. The purpose of this work is to characterize metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) in MRgRT systems at 0.345 T magnetic field strength. METHODS: A MOSFET dosimetry system, developed by Best Medical Canada for in‐vivo patient dosimetry, was used to study various commissioning tests performed on a MRgRT system, MRIdian(®) Linac. We characterized the MOSFET dosimeter with different cable lengths by determining its calibration factor, monitor unit linearity, angular dependence, field size dependence, percentage depth dose (PDD) variation, output factor change, and intensity modulated radiation therapy quality assurance (IMRT QA) verification for several plans. MOSFET results were analyzed and compared with commissioning data and Monte Carlo calculations. RESULTS: MOSFET measurements were not found to be affected by the presence of 0.345 T magnetic field. Calibration factors were similar for different cable length dosimeters either placed at the parallel or perpendicular direction to the magnetic field, with variations of less than 2%. The detector showed good linearity (R(2) = 0.999) for 100–600 MUs range. Output factor measurements were consistent with ionization chamber data within 2.2%. MOSFET PDD measurements were found to be within 1% for 1–15 cm depth range in comparison to ionization chamber. MOSFET normalized angular response matched thermoluminescent detector (TLD) response within 5.5%. The IMRT QA verification data for the MRgRT linac showed that the percentage difference between ionization chamber and MOSFET was 0.91%, 2.05%, and 2.63%, respectively for liver, spine, and mediastinum. CONCLUSION: MOSFET dosimeters are not affected by the 0.345 T magnetic field in MRgRT system. They showed physics parameters and performance comparable to TLD and ionization chamber; thus, they constitute an alternative to TLD for real‐time in‐vivo dosimetry in MRgRT procedures. John Wiley and Sons Inc. 2019-12-18 /pmc/articles/PMC6964768/ /pubmed/31854078 http://dx.doi.org/10.1002/acm2.12799 Text en © 2019 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 Measurements
Yadav, Poonam
Hallil, Abdelbasset
Tewatia, Dinesh
Dunkerley, David A. P.
Paliwal, Bhudatt
MOSFET dosimeter characterization in MR‐guided radiation therapy (MRgRT) Linac
title MOSFET dosimeter characterization in MR‐guided radiation therapy (MRgRT) Linac
title_full MOSFET dosimeter characterization in MR‐guided radiation therapy (MRgRT) Linac
title_fullStr MOSFET dosimeter characterization in MR‐guided radiation therapy (MRgRT) Linac
title_full_unstemmed MOSFET dosimeter characterization in MR‐guided radiation therapy (MRgRT) Linac
title_short MOSFET dosimeter characterization in MR‐guided radiation therapy (MRgRT) Linac
title_sort mosfet dosimeter characterization in mr‐guided radiation therapy (mrgrt) linac
topic Radiation Measurements
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6964768/
https://www.ncbi.nlm.nih.gov/pubmed/31854078
http://dx.doi.org/10.1002/acm2.12799
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