Patent ID: 7525104

Claim:
A particle beam irradiation method which uses both a depth direction irradiation field spread for spreading an irradiation field of a particle beam in a depth direction along an irradiation direction of the particle beam, and a lateral direction irradiation field spread for spreading the irradiation field of the particle beam in a lateral direction perpendicular to the irradiation direction of the particle beam, and which irradiates the particle beam on an irradiation target, wherein the depth direction irradiation field spread is an active irradiation field spread in which plural irradiation layers having different ranges in the irradiation direction of the particle beam are superimposed, the lateral direction irradiation field spread is an active irradiation spread in which irradiation spots of the particle beam are superimposed in the lateral direction, and a bolus having a shape along a deepest part of the irradiation target in the depth direction is disposed to cross the particle beam.