Volume-based dose optimization in brachytherapy

Purpose: We address the question of how to optimize the dwell time distribu tion in brachytherapy with a stepping source if a minimal tumor dose is pre scribed within the planning target volume (PTV), Methods and Materials: For a given PTV, reference points inside and at the surface of the PTV are generated and dose constraints are prescribed. The d ose at these reference points can be calculated if the positions of the sou rces are known. We determine a set of dwell times such that the dose constr aints are fulfilled, and at the same time, the total irradiation time is mi nimized. The simplex algorithm allows us to find a solution (if any exists) for this problem. Results: The performance of this method has been tested for a geometrically simple PTV, This method gives better results than conventionally used algo rithms for dwell time optimization. Conclusion: The method described in this paper allows a volume-oriented opt imization for brachytherapy dose distribution. The algorithm guarantees fin ding a dwell time distribution which fulfills the prescribed dose constrain ts, if any solution exists. (C) 1999 Elsevier Science Inc.