Updating of HIMAC beam delivery with broad beam method

Carbon ion radiotherapy at HIMAC started in 1994 using two horizontal and two vertical beam ports with broad beam method. The maximum beam energy extracted from accelerators was 400 MeV/n for the horizontal beam port, and 350 MeV/n for the vertical one. In recent years, the scope of diseases that can be treated by the carbon ion radiotherapy has widened and their tumor targets have varied in dimension and location. So, situations of shortage in the beam range in treatment planning have increased. In order to provide sufficient dose to the deeply seated target, we adopted higher energy beam, that is, 430 and 400 MeV/n for the horizontal port and the vertical port, respectively. For the introduction of the new energy beams, we carried out the following.