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Development of an ultra‐thin parallel plate ionization chamber for dosimetry in FLASH radiotherapy
BACKGROUND: Conventional air ionization chambers (ICs) exhibit ion recombination correction factors that deviate substantially from unity when irradiated with dose per pulse magnitudes higher than those used in conventional radiotherapy. This fact makes these devices unsuitable for the dosimetric ch...
Autores principales: | , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2022
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9545838/ https://www.ncbi.nlm.nih.gov/pubmed/35416306 http://dx.doi.org/10.1002/mp.15668 |
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author | Gómez, Faustino Gonzalez‐Castaño, Diego M. Fernández, Nicolás Gómez Pardo‐Montero, Juan Schüller, Andreas Gasparini, Alessia Vanreusel, Verdi Verellen, Dirk Felici, Giuseppe Kranzer, Rafael Paz‐Martín, Jose |
author_facet | Gómez, Faustino Gonzalez‐Castaño, Diego M. Fernández, Nicolás Gómez Pardo‐Montero, Juan Schüller, Andreas Gasparini, Alessia Vanreusel, Verdi Verellen, Dirk Felici, Giuseppe Kranzer, Rafael Paz‐Martín, Jose |
author_sort | Gómez, Faustino |
collection | PubMed |
description | BACKGROUND: Conventional air ionization chambers (ICs) exhibit ion recombination correction factors that deviate substantially from unity when irradiated with dose per pulse magnitudes higher than those used in conventional radiotherapy. This fact makes these devices unsuitable for the dosimetric characterization of beams in ultra‐high dose per pulse as used for FLASH radiotherapy. PURPOSE: We present the design, development, and characterization of an ultra‐thin parallel plate IC that can be used in ultra‐high dose rate (UHDR) deliveries with minimal recombination. METHODS: The charge collection efficiency (CCE) of parallel plate ICs was modeled through a numerical solution of the coupled differential equations governing the transport of charged carriers produced by ionizing radiation. It was used to find out the optimal parameters for the purpose of designing an IC capable of exhibiting a linear response with dose (deviation less than 1%) up to 10 Gy per pulse at 4 [Formula: see text] s pulse duration. As a proof of concept, two vented parallel plate IC prototypes have been built and tested in different ultra‐high pulse dose rate electron beams. RESULTS: It has been found that by reducing the distance between electrodes to a value of 0.25 mm it is possible to extend the dose rate operating range of parallel plate ICs to ultra‐high dose per pulse range, at standard voltage of clinical grade electrometers, well into several Gy per pulse. The two IC prototypes exhibit behavior as predicted by the numerical simulation. One of the so‐called ultra‐thin parallel plate ionization chamber (UTIC) prototypes was able to measure up to 10 Gy per pulse, 4 [Formula: see text] s pulse duration, operated at 300 V with no significant deviation from linearity within the uncertainties (ElectronFlash Linac, SIT). The other prototype was tested up to 5.4 Gy per pulse, 2.5 [Formula: see text] s pulse duration, operated at 250 V with CCE higher than 98.6% (Metrological Electron Accelerator Facility, MELAF at Physikalisch‐Technische Bundesanstalt, PTB). CONCLUSIONS: This work demonstrates the ability to extend the dose rate operating range of ICs to ultra‐high dose per pulse range by reducing the spacing between electrodes. The results show that UTICs are suitable for measurement in UHDR electron beams. |
format | Online Article Text |
id | pubmed-9545838 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2022 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-95458382022-10-14 Development of an ultra‐thin parallel plate ionization chamber for dosimetry in FLASH radiotherapy Gómez, Faustino Gonzalez‐Castaño, Diego M. Fernández, Nicolás Gómez Pardo‐Montero, Juan Schüller, Andreas Gasparini, Alessia Vanreusel, Verdi Verellen, Dirk Felici, Giuseppe Kranzer, Rafael Paz‐Martín, Jose Med Phys COMPUTATIONAL AND EXPERIMENTAL DOSIMETRY BACKGROUND: Conventional air ionization chambers (ICs) exhibit ion recombination correction factors that deviate substantially from unity when irradiated with dose per pulse magnitudes higher than those used in conventional radiotherapy. This fact makes these devices unsuitable for the dosimetric characterization of beams in ultra‐high dose per pulse as used for FLASH radiotherapy. PURPOSE: We present the design, development, and characterization of an ultra‐thin parallel plate IC that can be used in ultra‐high dose rate (UHDR) deliveries with minimal recombination. METHODS: The charge collection efficiency (CCE) of parallel plate ICs was modeled through a numerical solution of the coupled differential equations governing the transport of charged carriers produced by ionizing radiation. It was used to find out the optimal parameters for the purpose of designing an IC capable of exhibiting a linear response with dose (deviation less than 1%) up to 10 Gy per pulse at 4 [Formula: see text] s pulse duration. As a proof of concept, two vented parallel plate IC prototypes have been built and tested in different ultra‐high pulse dose rate electron beams. RESULTS: It has been found that by reducing the distance between electrodes to a value of 0.25 mm it is possible to extend the dose rate operating range of parallel plate ICs to ultra‐high dose per pulse range, at standard voltage of clinical grade electrometers, well into several Gy per pulse. The two IC prototypes exhibit behavior as predicted by the numerical simulation. One of the so‐called ultra‐thin parallel plate ionization chamber (UTIC) prototypes was able to measure up to 10 Gy per pulse, 4 [Formula: see text] s pulse duration, operated at 300 V with no significant deviation from linearity within the uncertainties (ElectronFlash Linac, SIT). The other prototype was tested up to 5.4 Gy per pulse, 2.5 [Formula: see text] s pulse duration, operated at 250 V with CCE higher than 98.6% (Metrological Electron Accelerator Facility, MELAF at Physikalisch‐Technische Bundesanstalt, PTB). CONCLUSIONS: This work demonstrates the ability to extend the dose rate operating range of ICs to ultra‐high dose per pulse range by reducing the spacing between electrodes. The results show that UTICs are suitable for measurement in UHDR electron beams. John Wiley and Sons Inc. 2022-04-22 2022-07 /pmc/articles/PMC9545838/ /pubmed/35416306 http://dx.doi.org/10.1002/mp.15668 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/4.0/This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | COMPUTATIONAL AND EXPERIMENTAL DOSIMETRY Gómez, Faustino Gonzalez‐Castaño, Diego M. Fernández, Nicolás Gómez Pardo‐Montero, Juan Schüller, Andreas Gasparini, Alessia Vanreusel, Verdi Verellen, Dirk Felici, Giuseppe Kranzer, Rafael Paz‐Martín, Jose Development of an ultra‐thin parallel plate ionization chamber for dosimetry in FLASH radiotherapy |
title | Development of an ultra‐thin parallel plate ionization chamber for dosimetry in FLASH radiotherapy |
title_full | Development of an ultra‐thin parallel plate ionization chamber for dosimetry in FLASH radiotherapy |
title_fullStr | Development of an ultra‐thin parallel plate ionization chamber for dosimetry in FLASH radiotherapy |
title_full_unstemmed | Development of an ultra‐thin parallel plate ionization chamber for dosimetry in FLASH radiotherapy |
title_short | Development of an ultra‐thin parallel plate ionization chamber for dosimetry in FLASH radiotherapy |
title_sort | development of an ultra‐thin parallel plate ionization chamber for dosimetry in flash radiotherapy |
topic | COMPUTATIONAL AND EXPERIMENTAL DOSIMETRY |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9545838/ https://www.ncbi.nlm.nih.gov/pubmed/35416306 http://dx.doi.org/10.1002/mp.15668 |
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