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A new algorithm for determining collimator angles that favor efficiency in MLC based IMRT delivery
Author(s) -
Wang David,
Hill R. W.,
Lam S.
Publication year - 2004
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1696708
Subject(s) - collimator , algorithm , multileaf collimator , dosimetry , histogram , head and neck , computer science , nuclear medicine , mathematics , optics , computer vision , physics , medicine , linear particle accelerator , beam (structure) , surgery , image (mathematics)
A new algorithm to determine collimator angles that favor delivery efficiency of intensity modulated radiotherapy plans was developed. It was found that the number of segments and monitor units (MUs) were largely reduced with the set of collimator angles determined with the new algorithm without compromising plan quality. The improvement of delivery efficiency using the new algorithm depends on the size and shape of the target(s), the number of modulation levels, and the type of leaf‐sequencing algorithm. In a typical prostate case, when a sweeping leaf‐sequencer is used for Varian 120 leaf (0.5×0.5 cm 2 beamlet), 80 leaf (1×1 cm 2 beamlet) and Elekta 40 leaf (1×1 cm 2 beamlet), the number of segments was reduced by 42%, 29%, and 5%, respectively. The number of MUs was reduced by 41%, 35%, and 10%. For the Siemens MLC (IMFAST™ leaf sequencer, 1×1 cm 2 beamlet) the segment reduction was 32% and the MU reduction was 14%. Comparison of the plans using the new and Brahme algorithms, in terms of target conformity index and dose volume histogram of the organs at risk, showed that the quality of the plans using the new algorithm was uncompromised. Similar results were obtained for a set of head and neck treatment plans.