Simulation Optimization Gantry Call-Back Control Method for Proton Therapy Systems

Proton therapy, a highly targeted radiation treatment for tumors, is experiencing high demand in recent years. Many studies focused more on improving patient throughput and proton beam utilization than treatment quality, especially in a multiple-gantry proton therapy facility that shares a proton beam accelerator. The beam sharing causes significantly long wait for a patient to receive beam treatment. This long beam wait in a gantry negatively impacts treatment quality and patient satisfaction. To reduce beam wait time while maximizing utilization, we propose a simulation optimization gantry call-back control (SOGCC) method to determine the optimal time to call a patient back to the gantry so that beam request conflicts can be improved without sacrificing much beam utilization. Simulation experiments are conducted to compare the proposed SOGCC method with other methods, such as the naive method, the gatekeeper method, and the rollout-based gantry call-back control (RGCC) method, and show a satisfactory performance of the SOGCC method. The simulation experiment also demonstrates how variation of setup time, beam treatment time and transition time, can undermine the performance of proton therapy systems, and the SOGCC method is able to account for the variation more efficiently. Evidently, the SOGCC method is a promising method to improve proton therapy system care delivery. Note to Practitioners-Proton therapy is an advanced radiation treatment technology that has been demonstrated effective in clinical settings. In current practice, its workflow efficiency and patient experience have not yet received enough attention. Proton therapy practitioners are seeking a high beam utilization and low beam wait time, which are difficult to achieve due to variation of time on each procedure. In this paper, we intend to improve the proton therapy delivery process by making use of real-time system state. Simulation is applied to predict the system dynamics and performance measures, and thus the optimal time to call patients back to gantry can be determined. This proposed method can be integrated into proton therapy systems to reduce beam request conflicts and patients beam wait time with small impact on beam utilization.