A study on beam flattening based on compact double scatterer applicable to rotational beam irradiation system in the proton therapy facility at CYRIC, Tohoku University

Proton therapy facility at Cyclotron and Radioisotope Center (CYRIC) in Tohoku University includes a horizontal beam line, currently used for research studies, and also a rotational beam irradiation system which is under construction. This system will be able to change the beam irradiation angle from 0 to 180 degree around the target and the beam delivery on the target volume is done passively using scatterers and ridge filters. In this rotational beam irradiation system due to the limitation on the available space between the beam exit window to the target location, a compact compensated contoured double scattering system was proposed to create the lateral homogeneous dose profile. This work represents the evaluation of this compact double scatterer and its application to the rotational beam irradiation system. The experiments were performed using the horizontal beam line by considering to the status of the rotational beam irradiation system in the target room 5 at CYRIC. The experimental results represent the lateral dose distribution with a proper treatment region which is in a good agreement with simulated data. (author)