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Correction for Ion Recombination in a Built-in Monitor Chamber of a Clinical Linear Accelerator at Ultra-High Dose Rates

Konradsson, Elise LU ; Ceberg, Crister LU orcid ; Lempart, Michael LU ; Blad, Börje LU ; Bäck, Sven LU ; Knöös, Tommy LU orcid and Petersson, Kristoffer LU (2020) In Radiation Research 194(6). p.580-586
Abstract

In the novel and promising radiotherapy technique known as FLASH, ultra-high dose-rate electron beams are used. As a step towards clinical trials, dosimetric advances will be required for accurate dose delivery of FLASH. The purpose of this study was to determine whether a built-in transmission chamber of a clinical linear accelerator can be used as a real-Time dosimeter to monitor the delivery of ultra-high-dose-rate electron beams. This was done by modeling the drop-in ion-collection efficiency of the chamber with increasing dose-per-pulse values, so that the ion recombination effect could be considered. The raw transmission chamber signal was extracted from the linear accelerator and its response was measured using radiochromic film... (More)

In the novel and promising radiotherapy technique known as FLASH, ultra-high dose-rate electron beams are used. As a step towards clinical trials, dosimetric advances will be required for accurate dose delivery of FLASH. The purpose of this study was to determine whether a built-in transmission chamber of a clinical linear accelerator can be used as a real-Time dosimeter to monitor the delivery of ultra-high-dose-rate electron beams. This was done by modeling the drop-in ion-collection efficiency of the chamber with increasing dose-per-pulse values, so that the ion recombination effect could be considered. The raw transmission chamber signal was extracted from the linear accelerator and its response was measured using radiochromic film at different dose rates/dose-per-pulse values, at a source-To-surface distance of 100 cm. An increase of the polarizing voltage, applied over the transmission chamber, by a factor of 2 and 3, improved the ion-collection efficiency, with corresponding increased efficiency at the highest dose-per-pulse values by a factor 1.4 and 2.2, respectively. The drop-in ion-collection efficiency with increasing dose-per-pulse was accurately modeled using a logistic function fitted to the transmission chamber data. The performance of the model was compared to that of the general theoretical Boag models of ion recombination in ionization chambers. The logistic model was subsequently used to correct for ion recombination at dose rates ranging from conventional to ultra-high, making the transmission chamber useful as a real-Time monitor for the dose delivery of FLASH electron beams in a clinical setup.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Radiation Research
volume
194
issue
6
pages
7 pages
publisher
Radiation Research Society
external identifiers
  • pmid:33348371
  • scopus:85097981491
ISSN
0033-7587
DOI
10.1667/RADE-19-00012
language
English
LU publication?
yes
id
7e3a5a8b-8fde-45e4-bcdd-edc4dd56c8ad
date added to LUP
2021-01-07 10:30:02
date last changed
2024-04-17 23:13:47
@article{7e3a5a8b-8fde-45e4-bcdd-edc4dd56c8ad,
  abstract     = {{<p>In the novel and promising radiotherapy technique known as FLASH, ultra-high dose-rate electron beams are used. As a step towards clinical trials, dosimetric advances will be required for accurate dose delivery of FLASH. The purpose of this study was to determine whether a built-in transmission chamber of a clinical linear accelerator can be used as a real-Time dosimeter to monitor the delivery of ultra-high-dose-rate electron beams. This was done by modeling the drop-in ion-collection efficiency of the chamber with increasing dose-per-pulse values, so that the ion recombination effect could be considered. The raw transmission chamber signal was extracted from the linear accelerator and its response was measured using radiochromic film at different dose rates/dose-per-pulse values, at a source-To-surface distance of 100 cm. An increase of the polarizing voltage, applied over the transmission chamber, by a factor of 2 and 3, improved the ion-collection efficiency, with corresponding increased efficiency at the highest dose-per-pulse values by a factor 1.4 and 2.2, respectively. The drop-in ion-collection efficiency with increasing dose-per-pulse was accurately modeled using a logistic function fitted to the transmission chamber data. The performance of the model was compared to that of the general theoretical Boag models of ion recombination in ionization chambers. The logistic model was subsequently used to correct for ion recombination at dose rates ranging from conventional to ultra-high, making the transmission chamber useful as a real-Time monitor for the dose delivery of FLASH electron beams in a clinical setup.</p>}},
  author       = {{Konradsson, Elise and Ceberg, Crister and Lempart, Michael and Blad, Börje and Bäck, Sven and Knöös, Tommy and Petersson, Kristoffer}},
  issn         = {{0033-7587}},
  language     = {{eng}},
  number       = {{6}},
  pages        = {{580--586}},
  publisher    = {{Radiation Research Society}},
  series       = {{Radiation Research}},
  title        = {{Correction for Ion Recombination in a Built-in Monitor Chamber of a Clinical Linear Accelerator at Ultra-High Dose Rates}},
  url          = {{http://dx.doi.org/10.1667/RADE-19-00012}},
  doi          = {{10.1667/RADE-19-00012}},
  volume       = {{194}},
  year         = {{2020}},
}