COMPARISON OF MIXED-INTEGER PROGRAMMING AND FAST SIMULATED ANNEALING FOR OPTIMIZING BEAM WEIGHTS IN RADIATION-THERAPY

Two competing methods for assigning intensities to radiation treatment beams were tested. One method was derived from mixed integer programm ing and the other was based on simulated annealing. The methods faced a common objective and identical constraints. The goal was to maximize the minimum tumor dose while keeping the dose in required fractions o f normal organ volumes below a threshold for damage. The minimum tumor doses of the two methods were compared when all the dose-volume const raints were satisfied. A mixed integer linear program gave a minimum t umor dose that was at least 1.8 Gy higher than that given by simulated annealing in 7 of 19 trials. The difference was greater than or equal to 5.4 Gy in 4 of 19 trials. In no case was the mixed integer solutio n one fraction size (1.8 Gy) worse than that of simulated annealing. T he better solution provided by the mixed integer program allows tumor dose to increase without violating the dose-volume limits of normal ti ssues. (C) 1996 American Association of Physicists in Medicine.