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A three‐dimensional algorithm for optimizing beam weights and wedge filters
Author(s) -
Xing Lei,
Hamilton R. J.,
Pelizzari C.,
Chen G. T. Y.
Publication year - 1998
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 - 10.1118/1.598375
Subject(s) - wedge (geometry) , superposition principle , beam (structure) , algorithm , mathematics , iterative method , iterative and incremental development , computer science , mathematical optimization , optics , physics , geometry , mathematical analysis , software engineering
An essential step towards optimizing and automating radiation therapy treatment planning is to develop an effective algorithm to find the optimal beam weights and wedge filters for a given set of beam directions and modalities. This problem is solved by introducing a variable transformation based on the universal and omni wedge principles. Instead of directly optimizing an objective function with respect to wedge angles and orientations, each field is first decomposed into a superposition of an open field and two orthogonal wedged fields. This transforms the problem of finding J beam weights, wedge angles, and orientations to that of optimizing a system with 3 J beam weights ( J open beams and 2 J nominal wedged beams), where J is the total number of incident beam directions. An iterative algorithm based on a method originally developed for image reconstruction is used to find the 3 J beam weights. The technique is applied to a few clinical cases. Treatment plans are improved compared to those obtained through the conventional manual trial and error planning process. In addition, planning time and effort are greatly reduced.