Patent ID: 8193520

Claim:
A particle beam therapy system comprising: a beam energy changing unit that changes the energy of an incident particle beam; a beam energy change control unit that outputs a command for controlling the beam energy changing unit; an irradiation unit that irradiates a particle beam exiting from the beam energy changing unit onto an irradiation subject; and an irradiation control unit that outputs a command for controlling the energy and position of a particle beam to be irradiated onto the irradiation subject, wherein the beam energy changing unit includes deflection electromagnets that sequentially deflect the incident particle beam into a plurality of intra-apparatus beam orbits, a plurality of separate variable energy attenuation units disposed in the respective intra-apparatus beam orbits, and a deflection electromagnet that performs deflection in such a way that particle beams that pass through the respective variable energy attenuation units fall into a single and the same orbit; and while a particle beam passes through one of the variable energy attenuation units, the beam energy change control unit performs control in such a way as to change the energy attenuation amount of at least one of the other variable energy attenuation units, based on the command from the irradiation control unit, each variable energy attenuation unit configured to change the energy attenuation amount without changing energy attenuation amounts of other variable energy attenuation units or a path of the particle beam passing through the variable energy attenuation unit.