Patent Number: 
Section: claims

1. A charged particle beam irradiation apparatus comprising:an irradiation section configured to irradiate an irradiated body with a charged particle beam;a multi-leaf collimator configured to set an irradiation range of the charged particle beam which is irradiated from the irradiation section;an imaging section that is provided so as to be able to advance and retreat with respect to an irradiation axis of the charged particle beam which is irradiated from the irradiation section, between the irradiation section and the multi-leaf collimator, and directly images an opening portion of the multi-leaf collimator; anda drive section configured to move the imaging section between an imaging position corresponding to an irradiation area which includes the irradiation axis of the charged particle beam and a retreated position away from the irradiation area. 2. The charged particle beam irradiation apparatus according to claim 1, wherein the imaging section is mounted on amounting bracket that can advance and retreat with respect to the irradiation axis of the charged particle beam,the drive section moves the mounting bracket between the imaging position and the retreated position, anda shield wall for protecting the imaging section from the charged particle beam is provided closer to the side of the irradiation axis of the charged particle beam than the imaging section in the mounting bracket when the mounting bracket is at the retreated position. 3. The charged particle beam irradiation apparatus according to claim 2, wherein a light source section configured to irradiate light to the opening portion of the multi-leaf collimator is further mounted on the mounting bracket. 4. The charged particle beam irradiation apparatus according to claim 3, wherein the light source section is mounted on the mounting bracket so as to be located on the irradiation axis of the charged particle beam when the mounting bracket is at the imaging position.