VERY FAST SIMULATED REANNEALING IN RADIATION-THERAPY TREATMENT PLAN OPTIMIZATION

Purpose: Very Fast Simulated Reannealing is a relatively new (1989) an d sophisticated algorithm for simulated annealing applications. It off ers the advantages of annealing methods while requiring shorter execut ion times. The purpose of this investigation was to adapt Very Past Si mulated Reannealing to conformal treatment planning optimization. Meth ods and Materials: We used Very Fast Simulated Reannealing to optimize treatments for three clinical cases with two different cost functions . The first cost function was linear (minimum target dose) with nonlin ear dose-volume normal tissue constraints. The second cost function (p robability of uncomplicated local control) was a weighted product of n ormal tissue complication probabilities and the tumor control probabil ity. Results: For the cost functions used in this study, the Very Fast Simulated Reannealing algorithm achieved results within 5-10% of the final solution (100,000 iterations) after 1000 iterations and within 3 -5% of the final solution after 5000-10000 iterations. These solutions were superior to those produced by a conventional treatment plan base d on an analysis of the resulting dose-volume histograms. However, thi s technique is a stochastic method and results vary in a statistical m anner. Successive solutions may differ by up to 10%. Conclusion: Very Fast Simulated Reannealing, with modifications, is suitable for radiat ion therapy treatment planning optimization. It produced results withi n 3-10% of the optimal solution, produced using another optimization a lgorithm (Mixed Integer Programming), in clinically useful execution t imes.