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Current status and future perspective of flattening filter free photon beams

Georg, Dietmar; Knöös, Tommy LU and McClean, Brendan (2011) In Medical Physics 38(3). p.1280-1293
Abstract
Purpose: Flattening filters (FFs) have been considered as an integral part of the treatment head of a medical accelerator for more than 50 years. The reasons for the longstanding use are, however, historical ones. Advanced treatment techniques, such as stereotactic radiotherapy or intensity modulated radiotherapy have stimulated the interest in operating linear accelerators in a flattening filter free (FFF) mode. The current manuscript reviews treatment head physics of FFF beams, describes their characteristics and the resulting potential advantages in their medical use, and closes with an outlook. Methods: A number of dosimetric benefits have been determined for FFF beams, which range from increased dose rate and dose per pulse to... (More)
Purpose: Flattening filters (FFs) have been considered as an integral part of the treatment head of a medical accelerator for more than 50 years. The reasons for the longstanding use are, however, historical ones. Advanced treatment techniques, such as stereotactic radiotherapy or intensity modulated radiotherapy have stimulated the interest in operating linear accelerators in a flattening filter free (FFF) mode. The current manuscript reviews treatment head physics of FFF beams, describes their characteristics and the resulting potential advantages in their medical use, and closes with an outlook. Methods: A number of dosimetric benefits have been determined for FFF beams, which range from increased dose rate and dose per pulse to favorable output ratio in-air variation with field size, reduced energy variation across the beam, and reduced leakage and out-of-field dose, respectively. Finally, the softer photon spectrum of unflattened beams has implications on imaging strategies and radiation protection. Results: The dosimetric characteristics of FFF beams have an effect on treatment delivery, patient comfort, dose calculation accuracy, beam matching, absorbed dose determination, treatment planning, machine specific quality assurance, imaging, and radiation protection. When considering conventional C-arm linacs in a FFF mode, more studies are needed to specify and quantify the clinical advantages, especially with respect to treatment plan quality and quality assurance. Conclusions: New treatment units are already on the market that operate without a FF or can be operated in a dedicated clinical FFF mode. Due to the convincing arguments of removing the FF, it is expected that more vendors will offer dedicated treatment units for advanced photon beam therapy in the near future. Several aspects related to standardization, dosimetry, treatment planning, and optimization need to be addressed in more detail in order to facilitate the clinical implementation of unflattened beams. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3554643] (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
unflattened beams, intensity modulated radiotherapy, stereotactic, radiotherapy, dosimetry
in
Medical Physics
volume
38
issue
3
pages
1280 - 1293
publisher
American Association of Physicists in Medicine
external identifiers
  • wos:000287879400017
  • scopus:79952148081
ISSN
0094-2405
DOI
10.1118/1.3554643
language
English
LU publication?
yes
id
9f53d3eb-0126-4b6d-a6da-2b12f2493ae3 (old id 1869044)
date added to LUP
2011-04-04 13:21:53
date last changed
2017-10-08 03:47:53
@article{9f53d3eb-0126-4b6d-a6da-2b12f2493ae3,
  abstract     = {Purpose: Flattening filters (FFs) have been considered as an integral part of the treatment head of a medical accelerator for more than 50 years. The reasons for the longstanding use are, however, historical ones. Advanced treatment techniques, such as stereotactic radiotherapy or intensity modulated radiotherapy have stimulated the interest in operating linear accelerators in a flattening filter free (FFF) mode. The current manuscript reviews treatment head physics of FFF beams, describes their characteristics and the resulting potential advantages in their medical use, and closes with an outlook. Methods: A number of dosimetric benefits have been determined for FFF beams, which range from increased dose rate and dose per pulse to favorable output ratio in-air variation with field size, reduced energy variation across the beam, and reduced leakage and out-of-field dose, respectively. Finally, the softer photon spectrum of unflattened beams has implications on imaging strategies and radiation protection. Results: The dosimetric characteristics of FFF beams have an effect on treatment delivery, patient comfort, dose calculation accuracy, beam matching, absorbed dose determination, treatment planning, machine specific quality assurance, imaging, and radiation protection. When considering conventional C-arm linacs in a FFF mode, more studies are needed to specify and quantify the clinical advantages, especially with respect to treatment plan quality and quality assurance. Conclusions: New treatment units are already on the market that operate without a FF or can be operated in a dedicated clinical FFF mode. Due to the convincing arguments of removing the FF, it is expected that more vendors will offer dedicated treatment units for advanced photon beam therapy in the near future. Several aspects related to standardization, dosimetry, treatment planning, and optimization need to be addressed in more detail in order to facilitate the clinical implementation of unflattened beams. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3554643]},
  author       = {Georg, Dietmar and Knöös, Tommy and McClean, Brendan},
  issn         = {0094-2405},
  keyword      = {unflattened beams,intensity modulated radiotherapy,stereotactic,radiotherapy,dosimetry},
  language     = {eng},
  number       = {3},
  pages        = {1280--1293},
  publisher    = {American Association of Physicists in Medicine},
  series       = {Medical Physics},
  title        = {Current status and future perspective of flattening filter free photon beams},
  url          = {http://dx.doi.org/10.1118/1.3554643},
  volume       = {38},
  year         = {2011},
}