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Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up

Mohammad Qutub, Richard Hugtenburg Orcid Logo, Ihsan Al-affan

Medical Physics, Volume: 47, Issue: 9, Pages: 4522 - 4530

Swansea University Authors: Mohammad Qutub, Richard Hugtenburg Orcid Logo, Ihsan Al-affan

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DOI (Published version): 10.1002/mp.14304

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AbstractPurposeThe determination of x‐ray spectra near the maze entrance of linear accelerator (LINAC) rooms is challenging due to the pulsed nature of the LINAC source. Mathematical methods to account for pulse pile‐up have been examined. These methods utilize the highly periodic pulsing structure...

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Published in: Medical Physics
ISSN: 0094-2405 2473-4209
Published: Wiley 2020
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URI: https://cronfa.swan.ac.uk/Record/cronfa55881
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Mathematical methods to account for pulse pile&#x2010;up have been examined. These methods utilize the highly periodic pulsing structure of the LINAC, differing from the effects of high&#x2010;intensity radioactive sources.MethodsSodium iodide (NaI) and plastic scintillation detectors were used to determine the energy spectra at different points near the maze entrance of a medical LINAC. Monte Carlo calculations of the energy distribution of scattered photons were used to simulate the energy spectrum at the maze entrance. The proposed algorithm uses the Monte Carlo code, FLUKA, to calculate a response function for both detectors. To determine the effects of the pile&#x2010;up in the spectra, the Poisson distribution was used, employing the average number of photons per pulse (&#x3BC;) interacting with the detector. The quantity, &#x3BC;, was obtained from the ratio of the number of events detected to the number of pulses delivered.The energy spectra at various distances from the maze entrance were measured using NaI and plastic scintillation detectors. From these measurements, the values of &#xB5; were calculated, and the pile&#x2010;up probability was determined. The FLUKA Monte Carlo code was used to calculate the spectrum at the maze entrance and the response matrices of the NaI and plastic scintillation detectors. The algorithm based on the Poisson distribution was applied to calculate the spectrum.ResultsThe agreement between the calculated and measured spectra was within the first standard deviation of the variance expected in &#xB5;. This agreement confirms that photons at the maze entrance have energies between 30 and 240 keV for a maze with three turns, with an average energy of around 85 keV. After pile&#x2010;up correction, the range of the pulse height distribution with the plastic scintillation detector, which has a low atomic number, was decreased (0 to 140 keV). In contrast, the range of the pulse height distribution with the NaI scintillation detector was closer to the photon spectrum (0 to 240 keV).ConclusionsThe corrected spectrum demonstrates that using a FLUKA Monte Carlo code and an algorithm based on the Poisson distribution are effective methods in removing the distortion due to the pile&#x2010;up in LINAC spectra when measuring with NaI and plastic scintillation detectors. 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spelling 2021-03-15T12:00:16.5269939 v2 55881 2020-12-11 Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up 5f1da18133cb6e7e96fcbcd5c8e37cfb Mohammad Qutub Mohammad Qutub true false efd2f52ea19cb047e01a01e6fa6fa54c 0000-0003-0352-9607 Richard Hugtenburg Richard Hugtenburg true false 8b20e64bf4213acb48ff8ceb777bfb1e Ihsan Al-affan Ihsan Al-affan true false 2020-12-11 MEDS AbstractPurposeThe determination of x‐ray spectra near the maze entrance of linear accelerator (LINAC) rooms is challenging due to the pulsed nature of the LINAC source. Mathematical methods to account for pulse pile‐up have been examined. These methods utilize the highly periodic pulsing structure of the LINAC, differing from the effects of high‐intensity radioactive sources.MethodsSodium iodide (NaI) and plastic scintillation detectors were used to determine the energy spectra at different points near the maze entrance of a medical LINAC. Monte Carlo calculations of the energy distribution of scattered photons were used to simulate the energy spectrum at the maze entrance. The proposed algorithm uses the Monte Carlo code, FLUKA, to calculate a response function for both detectors. To determine the effects of the pile‐up in the spectra, the Poisson distribution was used, employing the average number of photons per pulse (μ) interacting with the detector. The quantity, μ, was obtained from the ratio of the number of events detected to the number of pulses delivered.The energy spectra at various distances from the maze entrance were measured using NaI and plastic scintillation detectors. From these measurements, the values of µ were calculated, and the pile‐up probability was determined. The FLUKA Monte Carlo code was used to calculate the spectrum at the maze entrance and the response matrices of the NaI and plastic scintillation detectors. The algorithm based on the Poisson distribution was applied to calculate the spectrum.ResultsThe agreement between the calculated and measured spectra was within the first standard deviation of the variance expected in µ. This agreement confirms that photons at the maze entrance have energies between 30 and 240 keV for a maze with three turns, with an average energy of around 85 keV. After pile‐up correction, the range of the pulse height distribution with the plastic scintillation detector, which has a low atomic number, was decreased (0 to 140 keV). In contrast, the range of the pulse height distribution with the NaI scintillation detector was closer to the photon spectrum (0 to 240 keV).ConclusionsThe corrected spectrum demonstrates that using a FLUKA Monte Carlo code and an algorithm based on the Poisson distribution are effective methods in removing the distortion due to the pile‐up in LINAC spectra when measuring with NaI and plastic scintillation detectors. The agreement between the corrected and measured spectra indicates that Monte Carlo modeling can accurately determine the spectrum of a LINAC machine at the maze entrance. Journal Article Medical Physics 47 9 4522 4530 Wiley 0094-2405 2473-4209 pile‐up effect; radiation protection; radiotherapy maze entrance spectrum 25 9 2020 2020-09-25 10.1002/mp.14304 COLLEGE NANME Medical School COLLEGE CODE MEDS Swansea University 2021-03-15T12:00:16.5269939 2020-12-11T12:59:17.2870519 Faculty of Medicine, Health and Life Sciences Swansea University Medical School - Medicine Mohammad Qutub 1 Richard Hugtenburg 0000-0003-0352-9607 2 Ihsan Al-affan 3 55881__19148__c1012e794cdb424785cbe55a99b2fd33.pdf 55881.pdf 2021-01-21T15:33:03.7086104 Output 2181842 application/pdf Version of Record true © 2020 The Authors. This is an open access article under the terms of the Creative Commons Attribution License true eng http://creativecommons.org/licenses/by/4.0/
title Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up
spellingShingle Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up
Mohammad Qutub
Richard Hugtenburg
Ihsan Al-affan
title_short Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up
title_full Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up
title_fullStr Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up
title_full_unstemmed Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up
title_sort Determination of the photon spectrum of a therapeutic linear accelerator near the maze entrance: Comparison of Monte Carlo modeling and measurements using scintillation detectors corrected for pulse pile‐up
author_id_str_mv 5f1da18133cb6e7e96fcbcd5c8e37cfb
efd2f52ea19cb047e01a01e6fa6fa54c
8b20e64bf4213acb48ff8ceb777bfb1e
author_id_fullname_str_mv 5f1da18133cb6e7e96fcbcd5c8e37cfb_***_Mohammad Qutub
efd2f52ea19cb047e01a01e6fa6fa54c_***_Richard Hugtenburg
8b20e64bf4213acb48ff8ceb777bfb1e_***_Ihsan Al-affan
author Mohammad Qutub
Richard Hugtenburg
Ihsan Al-affan
author2 Mohammad Qutub
Richard Hugtenburg
Ihsan Al-affan
format Journal article
container_title Medical Physics
container_volume 47
container_issue 9
container_start_page 4522
publishDate 2020
institution Swansea University
issn 0094-2405
2473-4209
doi_str_mv 10.1002/mp.14304
publisher Wiley
college_str Faculty of Medicine, Health and Life Sciences
hierarchytype
hierarchy_top_id facultyofmedicinehealthandlifesciences
hierarchy_top_title Faculty of Medicine, Health and Life Sciences
hierarchy_parent_id facultyofmedicinehealthandlifesciences
hierarchy_parent_title Faculty of Medicine, Health and Life Sciences
department_str Swansea University Medical School - Medicine{{{_:::_}}}Faculty of Medicine, Health and Life Sciences{{{_:::_}}}Swansea University Medical School - Medicine
document_store_str 1
active_str 0
description AbstractPurposeThe determination of x‐ray spectra near the maze entrance of linear accelerator (LINAC) rooms is challenging due to the pulsed nature of the LINAC source. Mathematical methods to account for pulse pile‐up have been examined. These methods utilize the highly periodic pulsing structure of the LINAC, differing from the effects of high‐intensity radioactive sources.MethodsSodium iodide (NaI) and plastic scintillation detectors were used to determine the energy spectra at different points near the maze entrance of a medical LINAC. Monte Carlo calculations of the energy distribution of scattered photons were used to simulate the energy spectrum at the maze entrance. The proposed algorithm uses the Monte Carlo code, FLUKA, to calculate a response function for both detectors. To determine the effects of the pile‐up in the spectra, the Poisson distribution was used, employing the average number of photons per pulse (μ) interacting with the detector. The quantity, μ, was obtained from the ratio of the number of events detected to the number of pulses delivered.The energy spectra at various distances from the maze entrance were measured using NaI and plastic scintillation detectors. From these measurements, the values of µ were calculated, and the pile‐up probability was determined. The FLUKA Monte Carlo code was used to calculate the spectrum at the maze entrance and the response matrices of the NaI and plastic scintillation detectors. The algorithm based on the Poisson distribution was applied to calculate the spectrum.ResultsThe agreement between the calculated and measured spectra was within the first standard deviation of the variance expected in µ. This agreement confirms that photons at the maze entrance have energies between 30 and 240 keV for a maze with three turns, with an average energy of around 85 keV. After pile‐up correction, the range of the pulse height distribution with the plastic scintillation detector, which has a low atomic number, was decreased (0 to 140 keV). In contrast, the range of the pulse height distribution with the NaI scintillation detector was closer to the photon spectrum (0 to 240 keV).ConclusionsThe corrected spectrum demonstrates that using a FLUKA Monte Carlo code and an algorithm based on the Poisson distribution are effective methods in removing the distortion due to the pile‐up in LINAC spectra when measuring with NaI and plastic scintillation detectors. The agreement between the corrected and measured spectra indicates that Monte Carlo modeling can accurately determine the spectrum of a LINAC machine at the maze entrance.
published_date 2020-09-25T05:02:26Z
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score 11.3749895

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