Document Detail

Numerical solutions of the γ-index in two and three dimensions.
MedLine Citation:
PMID:  23044713     Owner:  NLM     Status:  MEDLINE    
The γ-index is used routinely to establish correspondence between two dose distributions. The definition of the γ-index can be written with a single equation but solving this equation at millions of points is computationally expensive, especially in three dimensions. Our goal is to extend the vector-equation method in Bakai et al (2003 Phys. Med. Biol.48 3543-53) to higher order for better accuracy and, as important, to determine the magnitude of accuracy in a higher order solution. We construct a numerical framework for calculating the γ-index in two and three dimensions and present an efficient method for calculating the γ-index with zeroth-, first- and second-order methods using tricubic spline interpolation. For an intensity-modulated radiation therapy example with 1.78 × 10⁶ voxels, the zeroth-order, first-order, first-order iterations and semi-second-order methods calculate the three-dimensional γ-index in 1.5, 4.7, 34.7 and 35.6 s with 36.7%, 1.1%, 0.2% and 0.8% accuracy, respectively. The accuracy of linear interpolation with this example is 1.0%. We present efficient numerical methods for calculating the three-dimensional γ-index with tricubic spline interpolation. The first-order method with iterations is the most accurate and fastest choice of the numerical methods if the dose distributions may have large second-order gradients. Furthermore, the difference between iterations can be used to determine the accuracy of the method.
Benjamin M Clasie; Gregory C Sharp; Joao Seco; Jacob B Flanz; Hanne M Kooy
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2012-10-09
Journal Detail:
Title:  Physics in medicine and biology     Volume:  57     ISSN:  1361-6560     ISO Abbreviation:  Phys Med Biol     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-10-17     Completed Date:  2013-03-18     Revised Date:  2013-11-14    
Medline Journal Info:
Nlm Unique ID:  0401220     Medline TA:  Phys Med Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  6981-97     Citation Subset:  IM    
Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
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MeSH Terms
Models, Theoretical*
Radiation Dosage*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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