Room: AAPM ePoster Library
For patient comfort and safety, irradiation times should be kept at a minimum while maintaining high treatment quality. In this study of HDR therapy with a vaginal cylinder, we used the Butterfly optimization algorithm (BOA) to simultaneously optimize individual dwell times for precise dose conformity and for the reduction of total dwell time.
BOA is a population-based, meta-heuristic algorithm that averts local minima by conducting intensive local and global search based on switching probability. We constructed an objective function (stimulus intensity function) that consisted of two components. The first one was the root-mean squared dose error (RMSE) defined as the square root of the sum of squared differences between prescribed and delivered dose at the constraint points. The second component was weighted total treatment time.
Four previously treated cases were retrospectively reviewed by re-optimizing the clinical treatment plans with BOA. Compared to the four original plans generated with the commercial adaptive volume optimization (AVOL) method, the BOA-optimized plans reduced treatment times by 5.4% to 8.3%, corresponding to time saving of 13.1seconds to 47.7 seconds with the activities on the treatment day and saving from 29.3 to 64.6 seconds if treated at activity of 5 Ci. Dose deviations from the prescription were smaller than in the original plans.
Dose optimizations based on the BOA algorithm yield closer dose conformity in vaginal HDR treatment than AVOL optimization. Incorporating total treatment time into the optimization algorithm reduces the delivery time while having only a small effect on dose conformity.