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Comparison of dose calculation algorithms in slab phantoms with cortical bone equivalent heterogeneities

Carrasco, Pablo; Jornet, Nuria; Duch, Maria Amor; Panettieri, V.; Weber, Lars LU ; Eudaldo, T.; Ginjaume, M. and Ribas, M. (2007) In Medical Physics 34(8). p.3323-3333
Abstract
To evaluate the dose values predicted by several calculation algorithms in two treatment planning systems, Monte Carlo (MC) simulations and measurements by means of various detectors were performed in heterogeneous layer phantoms with water- and bone-equivalent materials. Percentage depth doses (PDDs) were measured with thermoluminescent dosimeters (TLDs), metal-oxide semiconductor field-effect transistors (MOSFETs), plane parallel and cylindrical ionization chambers, and beam profiles with films. The MC code used for the simulations was the PENELOPE code. Three different field sizes (10 X 10, 5 X 5, and 2 X 2 cm 2) were studied in two phantom configurations and a bone equivalent material. These two phantom configurations contained... (More)
To evaluate the dose values predicted by several calculation algorithms in two treatment planning systems, Monte Carlo (MC) simulations and measurements by means of various detectors were performed in heterogeneous layer phantoms with water- and bone-equivalent materials. Percentage depth doses (PDDs) were measured with thermoluminescent dosimeters (TLDs), metal-oxide semiconductor field-effect transistors (MOSFETs), plane parallel and cylindrical ionization chambers, and beam profiles with films. The MC code used for the simulations was the PENELOPE code. Three different field sizes (10 X 10, 5 X 5, and 2 X 2 cm 2) were studied in two phantom configurations and a bone equivalent material. These two phantom configurations contained heterogeneities of 5 and 2 cm of bone, respectively. We analyzed the performance of four correction-based algorithms and one based on convolution superposition. The correction-based algorithms were the Batho, the Modified Batho, the Equivalent TAR implemented in the Cadplan (Varian) treatment planning system (TPS), and the Helax-TMS Pencil Beam from the Helax-TMS (Nucletron) TPS. The convolution-superposition algorithm was the Collapsed Cone implemented in the Helax-TMS. All the correction-based calculation algorithms underestimated the dose inside the bone-equivalent material for 18 MV compared to MC simulations. The maximum underestimation, in terms of root-mean-square (RMS), was about 15% for the Helax-TMS Pencil Beam (Helax-TMS PB) for a 2 X 2 cm2 field inside the bone-equivalent material. In contrast, the Collapsed Cone algorithm yielded values around 3%. A more complex behavior was found for 6 MV where the Collapsed Cone performed less well, overestimating the dose inside the heterogeneity in 3%-5%. The rebuildup in the interface bone-water and the penumbra shrinking in high-density media were not predicted by any of the calculation algorithms except the Collapsed Cone, and only the MC simulations matched the experimental values within the estimated uncertainties. The TLD and MOSFET detectors were suitable for dose measurement inside bone-equivalent materials, while parallel ionization chambers, applying the same calibration and correction factors as in water, systematically underestimated dose by 3%-5%. (c) 2007 American Association of Physicists in Medicine. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
keywords
heterogeneity correction, treatment planning systems, bone correction, calculation algorithms
in
Medical Physics
volume
34
issue
8
pages
3323 - 3333
publisher
American Association of Physicists in Medicine
external identifiers
  • wos:000248895500025
  • scopus:34547413594
ISSN
0094-2405
DOI
10.1118/1.2750972
language
English
LU publication?
yes
id
d0cb904e-b18d-4180-9cab-0c1a5a19285e (old id 691560)
date added to LUP
2007-12-05 16:07:35
date last changed
2017-07-23 04:37:12
@article{d0cb904e-b18d-4180-9cab-0c1a5a19285e,
  abstract     = {To evaluate the dose values predicted by several calculation algorithms in two treatment planning systems, Monte Carlo (MC) simulations and measurements by means of various detectors were performed in heterogeneous layer phantoms with water- and bone-equivalent materials. Percentage depth doses (PDDs) were measured with thermoluminescent dosimeters (TLDs), metal-oxide semiconductor field-effect transistors (MOSFETs), plane parallel and cylindrical ionization chambers, and beam profiles with films. The MC code used for the simulations was the PENELOPE code. Three different field sizes (10 X 10, 5 X 5, and 2 X 2 cm 2) were studied in two phantom configurations and a bone equivalent material. These two phantom configurations contained heterogeneities of 5 and 2 cm of bone, respectively. We analyzed the performance of four correction-based algorithms and one based on convolution superposition. The correction-based algorithms were the Batho, the Modified Batho, the Equivalent TAR implemented in the Cadplan (Varian) treatment planning system (TPS), and the Helax-TMS Pencil Beam from the Helax-TMS (Nucletron) TPS. The convolution-superposition algorithm was the Collapsed Cone implemented in the Helax-TMS. All the correction-based calculation algorithms underestimated the dose inside the bone-equivalent material for 18 MV compared to MC simulations. The maximum underestimation, in terms of root-mean-square (RMS), was about 15% for the Helax-TMS Pencil Beam (Helax-TMS PB) for a 2 X 2 cm2 field inside the bone-equivalent material. In contrast, the Collapsed Cone algorithm yielded values around 3%. A more complex behavior was found for 6 MV where the Collapsed Cone performed less well, overestimating the dose inside the heterogeneity in 3%-5%. The rebuildup in the interface bone-water and the penumbra shrinking in high-density media were not predicted by any of the calculation algorithms except the Collapsed Cone, and only the MC simulations matched the experimental values within the estimated uncertainties. The TLD and MOSFET detectors were suitable for dose measurement inside bone-equivalent materials, while parallel ionization chambers, applying the same calibration and correction factors as in water, systematically underestimated dose by 3%-5%. (c) 2007 American Association of Physicists in Medicine.},
  author       = {Carrasco, Pablo and Jornet, Nuria and Duch, Maria Amor and Panettieri, V. and Weber, Lars and Eudaldo, T. and Ginjaume, M. and Ribas, M.},
  issn         = {0094-2405},
  keyword      = {heterogeneity correction,treatment planning systems,bone correction,calculation algorithms},
  language     = {eng},
  number       = {8},
  pages        = {3323--3333},
  publisher    = {American Association of Physicists in Medicine},
  series       = {Medical Physics},
  title        = {Comparison of dose calculation algorithms in slab phantoms with cortical bone equivalent heterogeneities},
  url          = {http://dx.doi.org/10.1118/1.2750972},
  volume       = {34},
  year         = {2007},
}