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Modifying a clinical linear accelerator for delivery of ultra-high dose rate irradiation

Lempart, Michael LU ; Blad, Börje LU ; Adrian, Gabriel LU ; Bäck, Sven LU ; Knöös, Tommy LU ; Ceberg, Crister LU and Petersson, Kristoffer LU (2019) In Radiotherapy and Oncology 139. p.40-45
Abstract

Objectives: The purpose of this study was to modify a clinical linear accelerator, making it capable of electron beam ultra-high dose rate (FLASH) irradiation. Modifications had to be quick, reversible, and without interfering with clinical treatments. Methods: Performed modifications: (1) reduced distance with three setup positions, (2) adjusted/optimized gun current, modulator charge rate and beam steering values for a high dose rate, (3) delivery was controlled with a microcontroller on an electron pulse level, and (4) moving the primary and/or secondary scattering foils from the beam path. Results: The variation in dose for a five-pulse delivery was measured to be 1% (using a diode, 4% using film) during 10 minutes after a warm-up... (More)

Objectives: The purpose of this study was to modify a clinical linear accelerator, making it capable of electron beam ultra-high dose rate (FLASH) irradiation. Modifications had to be quick, reversible, and without interfering with clinical treatments. Methods: Performed modifications: (1) reduced distance with three setup positions, (2) adjusted/optimized gun current, modulator charge rate and beam steering values for a high dose rate, (3) delivery was controlled with a microcontroller on an electron pulse level, and (4) moving the primary and/or secondary scattering foils from the beam path. Results: The variation in dose for a five-pulse delivery was measured to be 1% (using a diode, 4% using film) during 10 minutes after a warm-up procedure, later increasing to 7% (11% using film). A FLASH irradiation dose rate was reached at the cross-hair foil, MLC, and wedge position, with ≥30, ≥80, and ≥300 Gy/s, respectively. Moving the scattering foils resulted in an increased output of ≥120, ≥250, and ≥1000 Gy/s, at the three positions. The beam flatness was 5% at the cross-hair position for a 20 × 20 and a 10 × 10 cm2 area, with and without both scattering foils in the beam. The beam flatness was 10% at the wedge position for a 6 and 2.5 cm diametric area, with and without the scattering foils in the beam path. Conclusions: A clinical accelerator was modified to produce ultra-high dose rates, high enough for FLASH irradiation. Future work aims to fine-tune the dose delivery, using the on-board transmission chamber signal and adjusting the dose-per-pulse.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
FLASH, Irradiation, Linac, Ultra-high dose rate
in
Radiotherapy and Oncology
volume
139
pages
40 - 45
publisher
Elsevier
external identifiers
  • scopus:85061177418
  • pmid:30755324
ISSN
0167-8140
DOI
10.1016/j.radonc.2019.01.031
project
FLASH - ultrahigh dose-rate radiotherapy: from in vitro to in vivo
language
English
LU publication?
yes
id
c58cf1bf-e057-4f32-a7ec-1e8701b50a0c
date added to LUP
2019-02-20 09:26:51
date last changed
2020-02-19 05:20:54
@article{c58cf1bf-e057-4f32-a7ec-1e8701b50a0c,
  abstract     = {<p>Objectives: The purpose of this study was to modify a clinical linear accelerator, making it capable of electron beam ultra-high dose rate (FLASH) irradiation. Modifications had to be quick, reversible, and without interfering with clinical treatments. Methods: Performed modifications: (1) reduced distance with three setup positions, (2) adjusted/optimized gun current, modulator charge rate and beam steering values for a high dose rate, (3) delivery was controlled with a microcontroller on an electron pulse level, and (4) moving the primary and/or secondary scattering foils from the beam path. Results: The variation in dose for a five-pulse delivery was measured to be 1% (using a diode, 4% using film) during 10 minutes after a warm-up procedure, later increasing to 7% (11% using film). A FLASH irradiation dose rate was reached at the cross-hair foil, MLC, and wedge position, with ≥30, ≥80, and ≥300 Gy/s, respectively. Moving the scattering foils resulted in an increased output of ≥120, ≥250, and ≥1000 Gy/s, at the three positions. The beam flatness was 5% at the cross-hair position for a 20 × 20 and a 10 × 10 cm<sup>2</sup> area, with and without both scattering foils in the beam. The beam flatness was 10% at the wedge position for a 6 and 2.5 cm diametric area, with and without the scattering foils in the beam path. Conclusions: A clinical accelerator was modified to produce ultra-high dose rates, high enough for FLASH irradiation. Future work aims to fine-tune the dose delivery, using the on-board transmission chamber signal and adjusting the dose-per-pulse.</p>},
  author       = {Lempart, Michael and Blad, Börje and Adrian, Gabriel and Bäck, Sven and Knöös, Tommy and Ceberg, Crister and Petersson, Kristoffer},
  issn         = {0167-8140},
  language     = {eng},
  month        = {02},
  pages        = {40--45},
  publisher    = {Elsevier},
  series       = {Radiotherapy and Oncology},
  title        = {Modifying a clinical linear accelerator for delivery of ultra-high dose rate irradiation},
  url          = {http://dx.doi.org/10.1016/j.radonc.2019.01.031},
  doi          = {10.1016/j.radonc.2019.01.031},
  volume       = {139},
  year         = {2019},
}