Patent ID: 8536548

Claim:
A particle beam therapy system comprising: an irradiation nozzle that scans a particle beam supplied from an accelerator and irradiates the particle beam in such a way as to enlarge an irradiation field; a multileaf collimator in which a pair of leaf rows, each being composed of a plurality of leaf plates laminated in a thickness direction, is arranged in such a way as to interpose a beam axis of the particle beam, in which respective side faces of the plurality of leaf plates, that face the beam axis, are driven in an approaching or in a departing direction with respect to the beam axis so that a predetermined opening shape (i) is formed, and that conforms the particle beam emitted from the irradiation nozzle to an irradiation subject and (ii) emits the particle beam; and an image-capturing unit that takes images of outer ends, of respective downstream side faces of the plurality of leaf plates in irradiation direction of the particle beam, that are distal with respect to the beam axis, wherein the image-capturing unit is provided for each of the pair of leaf rows, in such a way as to be situated at a position that is at an outer side of the irradiation field of the particle beam that has passed through the multileaf collimator and downstream of the multileaf collimator, and the image-capturing unit is adjusted in such a way that a foot of a perpendicular line from a viewpoint, of the image-capturing unit, to the downstream side face of a leaf plate, is situated at a position that is at an inner side of a position of an outer end of the leaf plate when the leaf plate is maximally driven in the departing direction.