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An efficient inverse radiotherapy planning method for VMAT using quadratic programming optimization.
MedLine Citation:
PMID:  22225315     Owner:  NLM     Status:  In-Data-Review    
Purpose: The purpose of this study is to investigate the feasibility of an inverse planning optimization approach for the Volumetric Modulated Arc Therapy (VMAT) based on quadratic programming and the projection method. The performance of this method is evaluated against a reference commercial planning system (eclipse(TM) for rapidarc(TM)) for clinically relevant cases.Methods: The inverse problem is posed in terms of a linear combination of basis functions representing arclet dose contributions and their respective linear coefficients as degrees of freedom. MLC motion is decomposed into basic motion patterns in an intuitive manner leading to a system of equations with a relatively small number of equations and unknowns. These equations are solved using quadratic programming under certain limiting physical conditions for the solution, such as the avoidance of negative dose during optimization and Monitor Unit reduction. The modeling by the projection method assures a unique treatment plan with beneficial properties, such as the explicit relation between organ weightings and the final dose distribution. Clinical cases studied include prostate and spine treatments. The optimized plans are evaluated by comparing isodose lines, DVH profiles for target and normal organs, and Monitor Units to those obtained by the clinical treatment planning system eclipse(TM).Results: The resulting dose distributions for a prostate (with rectum and bladder as organs at risk), and for a spine case (with kidneys, liver, lung and heart as organs at risk) are presented. Overall, the results indicate that similar plan qualities for quadratic programming (QP) and rapidarc(TM) could be achieved at significantly more efficient computational and planning effort using QP. Additionally, results for the quasimodo phantom [Bohsung et al., "IMRT treatment planning: A comparative inter-system and inter-centre planning exercise of the estro quasimodo group," Radiother. Oncol. 76(3), 354-361 (2005)] are presented as an example for an extreme concave case.Conclusion: Quadratic programming is an alternative approach for inverse planning which generates clinically satisfying plans in comparison to the clinical system and constitutes an efficient optimization process characterized by uniqueness and reproducibility of the solution.
W Hoegele; R Loeschel; N Merkle; P Zygmanski
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Medical physics     Volume:  39     ISSN:  0094-2405     ISO Abbreviation:  Med Phys     Publication Date:  2012 Jan 
Date Detail:
Created Date:  2012-01-09     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0425746     Medline TA:  Med Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  444     Citation Subset:  IM    
Department of Radiation Oncology, Regensburg University Medical Center, 93053 Regensburg, Germany and Department of Computer Science and Mathematics, Regensburg University of Applied Sciences, 93053 Regensburg, Germany.
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