The dose optimization algorithm based on anatomical points is developed to produce rapidly uniform doses over target distances generated on the target volume edges in high-dose-rate (HDR) brachytherapy stepping source application for a treatment length of 6 cm. Monte Carlo modeling of the 60Co HDR brachytherapy source and the surrounding medium were performed using PHITS code. The source dwell times were optimized using Tikhonov regularization in order to obtain uniform dose distribution at the anatomical points located at predefined target distances. The computed dose rates at distances from 0.25 up to 20 cm away from the source were first verified with the literature data sets. Then, the simulation results of the optimization process were compared to the calculations of commercial treatment planning system (TPS) SagiPlan. As a result, the dose uniformity was observed in the isodose curves at the target distances of 10 and 15 mm of the treatment length and the prescribed dose achieved the anatomical points uniformly. The algorithm developed in the present study can be applied for achieving the dose uniformity around the brachytherapy stepping source as a quicker tool for different treatment lengths and different target distances while maintaining the high quality of the treatment plans, saving time by avoiding the manual isodose shaping and then better suitable treatment for patients.
Keywords: Dose-optimization; High-dose-rate; Stepping-source; Tikhonov.