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Implementing multiple static field delivery for intensity modulated beams
Author(s) -
Wu Y.,
Yan D.,
Sharpe M. B.,
Miller B.,
Wong J. W.
Publication year - 2001
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 - 10.1118/1.1406515
Subject(s) - multileaf collimator , intensity (physics) , intensity modulation , cluster analysis , dosimetry , computer science , beam (structure) , algorithm , mathematical optimization , optics , mathematics , artificial intelligence , physics , nuclear medicine , linear particle accelerator , medicine , phase modulation , phase noise
A clinically oriented two‐dimensional intensity‐modulated beam delivery method is implemented using multiple static segmented fields, i.e., the “step‐and‐shoot” approach. Starting with a desired “ideal” intensity distribution, it creates a multiple‐level intensity approximation, and then constructs a sequence of segmented fields to deliver the multiple‐level intensities using multileaf collimator (MLC) and independent backup jaws. The approach starts with a simple grouping of all the nonzero intensity values into a minimum number of clusters for a user specified deviation tolerance for the ideal plan. The k ‐means clustering algorithm is then employed to find the optimal levels of intensity that minimize the discrepancies between the ideal and the approximated intensities, without violating the user specified deviation tolerance. The multiple‐level intensities are then decomposed into a sequence of machine deliverable segments. Apart from the first segment for each gantry angle, all the other segments are arranged to minimize the total travel distance of the leaves. The first segment covers the entire irradiated area and is used for treatment verification by electronic portal imaging. The implementation issues due to the physical constraints of the MLCs are also addressed.