The present invention provides an increased degree of uniformity of
radiation dose distribution for the interior of a diseased part. A
particle beam therapy
system includes a
charged particle beam generation apparatus and an
irradiation apparatus. An
ion beam is generated by the
charged particle beam generation apparatus. The
irradiation apparatus exposes a diseased part to the generated
ion beam. A scattering device, a range adjustment device, and a
Bragg peak spreading device are installed upstream of a first scanning
magnet and a second scanning
magnet. The scattering device and the range adjustment device are combined together and moved along a beam axis, whereas the
Bragg peak spreading device is moved independently along the beam axis. The scattering device moves to adjust the degree of
ion beam scattering. The range adjustment device moves to adjust
ion beam scatter changes caused by an absorber thickness adjustment. The
Bragg peak spreading device moves to adjust
ion beam scatter changes arising out of an SOBP device. These adjustments provide uniformity of
radiation dose distribution for the diseased part.