Purpose: We address the question of how to optimize the dwell time distribution in brachytherapy with a stepping source if a minimal tumor dose is prescribed 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 dose at these reference points can be calculated if the positions of the sources are known. We determine a set of dwell times such that the dose constraints are fulfilled, and at the same time, the total irradiation time is minimized. 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 algorithms for dwell time optimization.
Conclusion: The method described in this paper allows a volume-oriented optimization for brachytherapy dose distribution. The algorithm guarantees finding a dwell time distribution which fulfills the prescribed dose constraints, if any solution exists.