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Optimization of brachytherapy dose distributions by simulated annealing
Author(s) -
Sloboda Ron S.
Publication year - 1992
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 - 10.1118/1.596783
Subject(s) - simulated annealing , brachytherapy , dosimetry , radiation treatment planning , dose rate , algorithm , computer science , mathematical optimization , mathematics , nuclear medicine , physics , radiation therapy , medical physics , medicine
An algorithm based on the method of simulated annealing is presented for optimizing brachytherapy dose distributions. The algorithm accommodates either static configurations of multiple sources or single stepping sources, hence in principle can be used to optimize both low‐ and high‐dose rate treatments delivered with remote afterloading equipment. Required inputs include the specification of target dose rates and dose rate limits, expressed in absolute or relative terms, at operator selected points near the treatment site. The influence of the dose rate limits can be adjusted continuously through the use of one or more penalty factors. The algorithm generates a set of integer weights, one for each available source position, which are interpreted in terms of configuration occupancy numbers for static source arrangements and relative dwell times for stepping sources. Application is made to several variations of a hypothetical low‐dose rate vaginal vault planning problem involving one rectal and six applicator calculation points. The algorithm's performance for different source strengths, annealing schedules, target dose rates, dose rate limits, and values of a single penalty factor λ was examined. With a simple annealing schedule and value of λ=25, the algorithm found solutions of high quality for all problem variants. The CPU time required for optimization on a Vax 11/750 computer ranged from 2 min for a single configuration to 25 min for a solution consisting of four configurations. These results support the use of simulated annealing for clinical planning of low dose rate vaginal treatments, and encourage investigation of other applications in brachytherapy.