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Published in: Strahlentherapie und Onkologie 10/2018

01-10-2018 | Original Article

Automatic replanning of VMAT plans for different treatment machines: A template-based approach using constrained optimization

Authors: Luise A. Künzel, Oliver S. Dohm, Markus Alber, Daniel Zips, Daniela Thorwarth

Published in: Strahlentherapie und Onkologie | Issue 10/2018

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Abstract

Purpose

To investigate a new automatic template-based replanning approach combined with constrained optimization, which may be highly useful for a rapid plan transfer for planned or unplanned machine breakdowns. This approach was tested for prostate cancer (PC) and head-and-neck cancer (HNC) cases.

Methods

The constraints of a previously optimized volumetric modulated arc therapy (VMAT) plan were used as a template for automatic plan reoptimization for different accelerator head models. All plans were generated using the treatment planning system (TPS) Hyperion. Automatic replanning was performed for 16 PC cases, initially planned for MLC1 (4 mm MLC) and reoptimized for MLC2 (5 mm) and MLC3 (10 mm) and for 19 HNC cases, replanned from MLC2 to MLC3. EUD, Dmean, D2%, and D98% were evaluated for targets; for OARs EUD and D2% were analyzed. Replanning was considered successful if both plans fulfilled equal constraints.

Results

All prostate cases were successfully replanned. The mean relative target EUD deviation was −0.15% and −0.57% for replanning to MLC2 and MLC3, respectively. OAR sparing was successful in all cases. Replanning of HNC cases from MLC2 to MLC3 was successful in 16/19 patients with a mean decrease of −0.64% in PTV60 EUD. In three cases target doses were substantially decreased by up to −2.58% (PTV60) and −3.44% (PTV54), respectively. Nevertheless, OAR sparing was always achieved as planned.

Conclusions

Automatic replanning of VMAT plans for a different treatment machine by using pre-existing constraints as a template for a reoptimization is feasible and successful in terms of equal constraints.
Appendix
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Literature
21.
go back to reference Alber M, Birkner M, Nüsslin F (2002) Tools for the analysis of dose optimization: II. Sensitivity analysis. Phys Med Biol 47:N265CrossRef Alber M, Birkner M, Nüsslin F (2002) Tools for the analysis of dose optimization: II. Sensitivity analysis. Phys Med Biol 47:N265CrossRef
Metadata
Title
Automatic replanning of VMAT plans for different treatment machines: A template-based approach using constrained optimization
Authors
Luise A. Künzel
Oliver S. Dohm
Markus Alber
Daniel Zips
Daniela Thorwarth
Publication date
01-10-2018
Publisher
Springer Berlin Heidelberg
Published in
Strahlentherapie und Onkologie / Issue 10/2018
Print ISSN: 0179-7158
Electronic ISSN: 1439-099X
DOI
https://doi.org/10.1007/s00066-018-1319-x

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