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Beam modeling and verification of a photon beam multisource model

Ahnesjö, Anders; Weber, Lars LU ; Murman, Anders; Saxner, Mikael; Thorslund, Ingvar and Traneus, Erik (2005) In Medical Physics 32(6). p.1722-1737
Abstract
Dose calculations for treatment planning of photon beam radiotherapy require a model of the beam to drive the dose calculation models. The beam shaping process involves scattering and filtering that yield radiation components which vary with collimator settings. The necessity to model these components has motivated the development of multisource beam models. We describe and evaluate clinical photon beam modeling based on multisource models, including lateral beam quality variations. The evaluation is based on user data for a pencil kernel algorithm and a point kernel algorithm (collapsed cone) used in the clinical treatment planning systems Helax-TMS and Nucletron-Oncentra. The pencil kernel implementations treat the beam spectrum as... (More)
Dose calculations for treatment planning of photon beam radiotherapy require a model of the beam to drive the dose calculation models. The beam shaping process involves scattering and filtering that yield radiation components which vary with collimator settings. The necessity to model these components has motivated the development of multisource beam models. We describe and evaluate clinical photon beam modeling based on multisource models, including lateral beam quality variations. The evaluation is based on user data for a pencil kernel algorithm and a point kernel algorithm (collapsed cone) used in the clinical treatment planning systems Helax-TMS and Nucletron-Oncentra. The pencil kernel implementations treat the beam spectrum as lateral invariant while the collapsed cone involves off axis softening of the spectrum. Both algorithms include modeling of head scatter components. The parameters of the beam model are derived from measured beam data in a semiautomatic process called RDH (radiation data handling) that, in sequential steps, minimizes the deviations in calculated dose versus the measured data. The RDH procedure is reviewed and the results of processing data from a large number of treatment units are analyzed for the two dose calculation algorithms. The results for both algorithms are similar, with slightly better results for the collapsed cone implementations. For open beams, 87% of the machines have maximum errors less than 2.5%. For wedged beams the errors were found to increase with increasing wedge angle. Internal, motorized wedges did yield slightly larger errors than external wedges. These results reflect the increased complexity, both experimentally and computationally, when wedges are used compared to open beams. (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
beam modeling, convolution/superposition, verification
in
Medical Physics
volume
32
issue
6
pages
1722 - 1737
publisher
American Association of Physicists in Medicine
external identifiers
  • pmid:16013730
  • wos:000229908600031
  • scopus:21144440478
ISSN
0094-2405
DOI
10.1118/1.1898485
language
English
LU publication?
yes
id
d2b05c56-3a35-4d90-9700-4c39d7c4b134 (old id 223654)
alternative location
http://dx.doi.org/10.1118/1.1898485
date added to LUP
2007-08-06 13:40:06
date last changed
2017-01-01 06:54:17
@article{d2b05c56-3a35-4d90-9700-4c39d7c4b134,
  abstract     = {Dose calculations for treatment planning of photon beam radiotherapy require a model of the beam to drive the dose calculation models. The beam shaping process involves scattering and filtering that yield radiation components which vary with collimator settings. The necessity to model these components has motivated the development of multisource beam models. We describe and evaluate clinical photon beam modeling based on multisource models, including lateral beam quality variations. The evaluation is based on user data for a pencil kernel algorithm and a point kernel algorithm (collapsed cone) used in the clinical treatment planning systems Helax-TMS and Nucletron-Oncentra. The pencil kernel implementations treat the beam spectrum as lateral invariant while the collapsed cone involves off axis softening of the spectrum. Both algorithms include modeling of head scatter components. The parameters of the beam model are derived from measured beam data in a semiautomatic process called RDH (radiation data handling) that, in sequential steps, minimizes the deviations in calculated dose versus the measured data. The RDH procedure is reviewed and the results of processing data from a large number of treatment units are analyzed for the two dose calculation algorithms. The results for both algorithms are similar, with slightly better results for the collapsed cone implementations. For open beams, 87% of the machines have maximum errors less than 2.5%. For wedged beams the errors were found to increase with increasing wedge angle. Internal, motorized wedges did yield slightly larger errors than external wedges. These results reflect the increased complexity, both experimentally and computationally, when wedges are used compared to open beams.},
  author       = {Ahnesjö, Anders and Weber, Lars and Murman, Anders and Saxner, Mikael and Thorslund, Ingvar and Traneus, Erik},
  issn         = {0094-2405},
  keyword      = {beam modeling,convolution/superposition,verification},
  language     = {eng},
  number       = {6},
  pages        = {1722--1737},
  publisher    = {American Association of Physicists in Medicine},
  series       = {Medical Physics},
  title        = {Beam modeling and verification of a photon beam multisource model},
  url          = {http://dx.doi.org/10.1118/1.1898485},
  volume       = {32},
  year         = {2005},
}