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Real-time dynamic MLC tracking for inversely optimized arc radiotherapy

Falk, Marianne ; af Rosenschöld, Per Munck LU orcid ; Keall, Paul ; Cattell, Herbert ; Cho, Byung Chul ; Poulsen, Per ; Povzner, Sergey ; Sawant, Amit ; Zimmerman, Jens and Korreman, Stine (2010) In Radiotherapy and Oncology 94(2). p.218-223
Abstract

Background and purpose: Motion compensation with MLC tracking was tested for inversely optimized arc radiotherapy with special attention to the impact of the size of the target displacements and the angle of the leaf trajectory. Materials and methods: An MLC-tracking algorithm was used to adjust the MLC positions according to the target movements using information from an optical real-time positioning management system. Two plans with collimator angles of 45° and 90°, respectively, were delivered and measured using the Delta4® dosimetric device moving in the superior-inferior direction with peak-to-peak displacements of 5, 10, 15, 20 and 25 mm and a cycle time of 6 s. Results: Gamma index evaluation for plan delivery with MLC... (More)

Background and purpose: Motion compensation with MLC tracking was tested for inversely optimized arc radiotherapy with special attention to the impact of the size of the target displacements and the angle of the leaf trajectory. Materials and methods: An MLC-tracking algorithm was used to adjust the MLC positions according to the target movements using information from an optical real-time positioning management system. Two plans with collimator angles of 45° and 90°, respectively, were delivered and measured using the Delta4® dosimetric device moving in the superior-inferior direction with peak-to-peak displacements of 5, 10, 15, 20 and 25 mm and a cycle time of 6 s. Results: Gamma index evaluation for plan delivery with MLC tracking gave a pass rate higher than 98% for criteria 3% and 3 mm for both plans and for all sizes of the target displacement. With no motion compensation, the average pass rate was 75% for plan 1 and 70% for plan 2 for 25 mm peak-to-peak displacement. Conclusion: MLC tracking improves the accuracy of inversely optimized arc delivery for the cases studied. With MLC tracking, the dosimetric accuracy was independent of the magnitude of the peak-to-peak displacement of the target and not significantly affected by the angle between the leaf trajectory and the target movements.

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author
; ; ; ; ; ; ; ; and
publishing date
type
Contribution to journal
publication status
published
subject
keywords
MLC, Motion, RapidArc, Tracking
in
Radiotherapy and Oncology
volume
94
issue
2
pages
218 - 223
publisher
Elsevier
external identifiers
  • pmid:20089322
  • scopus:77249161672
ISSN
0167-8140
DOI
10.1016/j.radonc.2009.12.022
language
English
LU publication?
no
additional info
Funding Information: The authors wish to acknowledge Dan Ruan (Stanford) for her involvement in the development of MLC tracking implemented in this study. The authors would also like to thank Michelle Svatos (Varian) and Scott Johnson (Varian) for their help in getting this project started, and for their continuous support of it. Thanks to Thomas Carlslund (Rigshospitalet) and Mikael Olsen (Rigshospitalet) for technical support during the installation of the tracking system at Rigshospitalet. Finally thanks to Gitte Persson for technical assistance and to Anna Fredh for reviewing the manuscript and improving the clarity. Research support from Varian Medical Systems and CIRRO – The Lundbeck Foundation Center for Interventional Research in Radiation Oncology and The Danish Council for Strategic Research are gratefully acknowledged. Varian Medical Systems contributed to the study with detailed information regarding use of the RPM system. The manuscript was reviewed by Varian Medical Systems prior to submission as is.
id
0d756975-9267-4d40-b73e-9b7857f53976
date added to LUP
2023-07-19 17:03:59
date last changed
2024-04-05 21:22:42
@article{0d756975-9267-4d40-b73e-9b7857f53976,
  abstract     = {{<p>Background and purpose: Motion compensation with MLC tracking was tested for inversely optimized arc radiotherapy with special attention to the impact of the size of the target displacements and the angle of the leaf trajectory. Materials and methods: An MLC-tracking algorithm was used to adjust the MLC positions according to the target movements using information from an optical real-time positioning management system. Two plans with collimator angles of 45° and 90°, respectively, were delivered and measured using the Delta<sup>4</sup>® dosimetric device moving in the superior-inferior direction with peak-to-peak displacements of 5, 10, 15, 20 and 25 mm and a cycle time of 6 s. Results: Gamma index evaluation for plan delivery with MLC tracking gave a pass rate higher than 98% for criteria 3% and 3 mm for both plans and for all sizes of the target displacement. With no motion compensation, the average pass rate was 75% for plan 1 and 70% for plan 2 for 25 mm peak-to-peak displacement. Conclusion: MLC tracking improves the accuracy of inversely optimized arc delivery for the cases studied. With MLC tracking, the dosimetric accuracy was independent of the magnitude of the peak-to-peak displacement of the target and not significantly affected by the angle between the leaf trajectory and the target movements.</p>}},
  author       = {{Falk, Marianne and af Rosenschöld, Per Munck and Keall, Paul and Cattell, Herbert and Cho, Byung Chul and Poulsen, Per and Povzner, Sergey and Sawant, Amit and Zimmerman, Jens and Korreman, Stine}},
  issn         = {{0167-8140}},
  keywords     = {{MLC; Motion; RapidArc; Tracking}},
  language     = {{eng}},
  number       = {{2}},
  pages        = {{218--223}},
  publisher    = {{Elsevier}},
  series       = {{Radiotherapy and Oncology}},
  title        = {{Real-time dynamic MLC tracking for inversely optimized arc radiotherapy}},
  url          = {{http://dx.doi.org/10.1016/j.radonc.2009.12.022}},
  doi          = {{10.1016/j.radonc.2009.12.022}},
  volume       = {{94}},
  year         = {{2010}},
}