Patent Number: 
Section: claims

1. 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; andan 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, whereinthe 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, andthe 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. 2. The particle beam therapy system according to claim 1, wherein the image-capturing unit has a mirror that reflects an image of the outer end of the leaf plate and an image-capturing device provided apart from the mirror,and arrangement of the mirror and the image-capturing device is adjusted, based on a virtual image of the viewpoint of the image-capturing device, that is caused by reflection of the mirror. 3. The particle beam therapy system according to claim 2, wherein the image-capturing unit is adjusted in such a way that the foot of a perpendicular line from the viewpoint to the downstream side face is located at a position that is closer to a position of the outer end at a time when the leaf plate is moved to a middle of driving range than to a position of the outer end at a time when the leaf plate is maximally moved in the approaching direction. 4. The particle beam therapy system according to claim 3, wherein each of the plurality of leaf plates is formed in such a way that at least a portion, of an outer side face of the leaf plate, that is adjacent to the downstream side face, has an acute angle with respect to the downstream side face. 5. The particle beam therapy system according to claim 4, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 6. The particle beam therapy system according to claim 3, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 7. The particle beam therapy system according to claim 2, wherein the image-capturing unit is adjusted in such a way that the foot of a perpendicular line from the viewpoint to the downstream side face is located at a position that is closer to a position of the outer end at a time when the leaf plate is maximally moved in the approaching direction than to a position of the outer end at a time when the leaf plate is moved to a middle of driving range. 8. The particle beam therapy system according to claim 7, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 9. The particle beam therapy system according to claim 2, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 10. The particle beam therapy system according to claim 1, wherein the image-capturing unit is adjusted in such a way that the foot of a perpendicular in from the viewpoint to the downstream side face is located at a position that is closer to a position of the outer end at a time when the leaf plate is moved to a middle of driving range than to a position of the outer end at a time when the leaf plate is maximally moved in the approaching direction. 11. The particle beam therapy system according to claim 10, wherein each of the plurality of leaf plates is formed in such a way that at least a portion, of an outer side face of the leaf plate, that is adjacent to the downstream side face, has an acute angle with respect to the downstream side face. 12. The particle beam therapy system according to claim 11, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 13. The particle beam therapy system according to claim 10, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 14. The particle beam therapy system according to claim 1, wherein the image-capturing unit is adjusted in such a way that the foot of a perpendicular line from the viewpoint to the downstream side face is located at a position that is closer to a position of the outer end at a time when the leaf plate is maximally moved in the approaching direction than to a position of the outer end at a time when the leaf plate is moved to a middle of driving range. 15. The particle beam therapy system according to claim 14, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape. 16. The particle beam therapy system according to claim 1, further including an image processing unit that determines the position of the outer end, based on an image taken by the image-capturing unit, and performs conversion processing in which the position of the outer end is converted into data that indicates the opening shape.