Shortening treatment time for proton therapy can improve the treatment efficiency and efficacy. Energy layer switching time (ELST) is the main contributor to the delivery time, including the dose delivery time and spot switching time. In this paper, we propose a general dynamic ridge filter (D-RiFi) to broaden the width of the pristine-Bragg peak, which can significantly reduce the layers and ELST. By optimizing the shape of D-RiFi, the maximum width of the Bragg peak can be extended to 3.16 cm with a dose flatness of 2.3%. The placement of D-RiFi also influences the beam size and lateral dose uniformity at the isocenter. According to the Monte Carlo simulation of the treatment head, the D-RiFi should be placed 50cm away from the isocenter to satisfy the dose uniformity of 2.5%.  Furthermore, since the broadening energy spread after the scattering with D-RiFi, the number of energy stacking layers can be reduced by 80.95 % from 21 to 4, which is conducive to realizing fast proton therapy and some advanced motion-control techniques (e.g. volume repainting, real-time tumor tracking).

proton therapy,energy layer number optimization,dynamic ridge filter,MonteCarlo Simulation