Patent Number: 
Section: claims

1. A multi-leaf collimator that narrows a radiation field to a predetermined shape comprising:leaf blocks movable in the direction of scaling the radiation field and having a pattern drawn along the direction of movement on a predetermined surface; anda detection part configured to acquire images of the pattern included in a region along said predetermined surface and to detect displacement of said leaf blocks based on a temporal change of said images. 2. A multi-leaf collimator according to claim 1, wherein said pattern has specific markings at predetermined locations, andsaid detection part specifies the arranged locations of said pattern according to said specific markings. 3. A multi-leaf collimator according to claim 1, wherein said detection part comprises:a radiation part irradiating a beam in the direction of said predetermined surface;image sensors subject to light reflected from the direction of said predetermined surface and acquiring said images; anda displacement acquisition part acquiring displacement of said leaf blocks from the pattern existing in said images. 4. The multi-leaf collimator according to claim 3, wherein said displacement acquisition part comprises:a recognition part recognizing the arranged locations of the pattern existing in said images; anda comparison part acquiring differences between images of the pattern by comparing the arranged locations of the pattern existing in an image acquired previously and the arranged locations of the pattern existing in an image currently acquired, wherein,displacement of said leaf blocks is acquired from said difference. 5. A multi-leaf collimator according to claim 3, wherein a plurality of said leaf blocks is arranged in parallel, andsaid radiation part and said image sensors placed corresponding to predetermined leaf blocks and said radiation part and said image sensors placed corresponding to other leaf blocks adjacent to the predetermined leaf blocks, are differently arranged in line at the locations of placement. 6. A multi-leaf collimator according to claim 3, wherein a plurality of said leaf blocks is arranged in parallel,a plurality of said radiation parts are placed corresponding to each leaf block in pairs,a plurality of said image sensors are placed corresponding to said radiation part in pairs,said radiation part irradiates a beam with a wavelength different from that of said radiation part corresponding to the other leaf blocks adjacent to corresponding leaf blocks, andsaid image sensors are provided with filters for transilluminating a beam with a wavelength irradiated by a pair of said radiation part. 7. A multi-leaf collimator according to claim 3, wherein a plurality of said leaf blocks is arranged in parallel,a plurality of said radiation parts are placed corresponding to each leaf block in pairs,a plurality of said image sensors are placed corresponding to said radiation part in pairs,said radiation part irradiates a beam with a wavelength different from that of said radiation part corresponding to the other leaf blocks adjacent to corresponding leaf blocks, andsaid detection part further comprises an extraction part acquiring images obtained by irradiation of the radiation part, by extracting only images created by a beam with a wavelength irradiated by said radiation part paired with the image sensors. 8. A multi-leaf collimator that narrows a radiation field to a predetermined shape comprising:leaf blocks movable in the direction of scaling the radiation field and having a pattern drawn along the direction of movement on a predetermined surface; anda detection part configured to acquire images of the pattern included in a region along said predetermined surface and to detect locations of said leaf blocks based on a temporal change of said images. 9. A multi-leaf collimator according to claim 8, wherein said pattern has location-specific markings in parallel along a drawing area, andsaid detection part specifies the arranged locations of said pattern according to said location-specific markings. 10. A multi-leaf collimator according to claim 8, wherein said detection part comprises:a radiation part irradiating a beam in the direction of said predetermined surface;image sensors subject to light reflected from the direction of said predetermined surface and acquiring said images; anda location acquisition part acquiring the locations of said leaf blocks from the pattern existing in said images. 11. A multi-leaf collimator according to claim 10, wherein said location acquisition part comprises:a recognition part recognizing the arranged locations of the pattern existing in said images, wherein,the locations of said leaf blocks are acquired according to the arranged locations of said pattern. 12. A multi-leaf collimator according to claim 10, wherein a plurality of said leaf blocks is arranged in parallel, andsaid radiation part and said image sensors placed corresponding to predetermined leaf blocks and said radiation part and said image sensors placed corresponding to the other leaf blocks adjacent to the predetermined leaf blocks, are differently arranged in line at the locations of placement. 13. A multi-leaf collimator according to claim 10, wherein a plurality of said leaf blocks is arranged in parallel,a plurality of said radiation parts are placed corresponding to each leaf block in pairs,a plurality of said image sensors are placed corresponding to said radiation part in pairs,said radiation part irradiates a beam with a wavelength different from that of said radiation part corresponding to the other leaf blocks adjacent to corresponding leaf blocks, andsaid image sensors are provided with filters for transilluminating a beam with a wavelength irradiated by a pair of said radiation part. 14. A multi-leaf collimator according to claim 10, wherein a plurality of said leaf blocks is arranged in parallel,a plurality of said radiation parts are placed corresponding to each leaf block in pairs,a plurality of said image sensors are placed corresponding to said radiation part in pairs,said radiation part irradiates a beam with a wavelength different from that of said radiation part corresponding to the other leaf blocks adjacent to corresponding leaf blocks, andsaid detection part further comprises an extraction part acquiring an image obtained by irradiation from the radiation part, by extracting only images created by a beam with a wavelength irradiated by said radiation part paired with the image sensors. 15. A radiotherapy unit comprising:a radiation source for irradiating radiation;a bed on which to place an object; anda multi-leaf collimator between said radiation source and said bed, narrowing a radiation field to a predetermined shape, said multi-leaf collimator comprising:leaf blocks movable in the direction of scaling the radiation field and having a pattern drawn along the direction of movement on a predetermined surface; anda detection part configured to acquire images of the pattern included in a region along said predetermined surface and to detect displacement of said leaf blocks based on a temporal change of said images. 16. A radiotherapy unit according to claim 15, wherein said pattern has specific markings at predetermined locations, andsaid detection part specifies the arranged locations of said pattern according to said specific markings. 17. A radiotherapy unit according to claim 15, wherein said detection part comprises:a radiation part irradiating a beam in the direction of said predetermined surface;image sensors subject to light reflected from the direction of said predetermined surface and acquiring said images; anda displacement acquisition part acquiring displacement of said leaf blocks from the pattern existing in said images. 18. A radiotherapy unit according to claim 17, wherein said displacement acquisition part comprises:a recognition part recognizing the arranged locations of the pattern existing in said images; anda comparison part acquiring the difference between images of the pattern by comparing the arranged locations of the pattern existing in an image acquired previously and the arranged locations of the pattern images existing in an image currently acquired, and acquiring displacement of said leaf blocks from said difference. 19. A radiotherapy unit according to claim 17, wherein a plurality of said leaf blocks is arranged in parallel, andsaid radiation part and said image sensors placed corresponding to predetermined leaf blocks and said radiation part, and said image sensors placed corresponding to the other leaf blocks adjacent to the predetermined leaf blocks, are differently arranged in line at the locations of placement. 20. A radiotherapy unit according to claim 17, wherein a plurality of said leaf blocks is arranged in parallel,a plurality of said radiation parts are placed corresponding to each leaf block in pairs, a plurality of said image sensors are placed corresponding to said radiation part in pairs,said radiation part irradiates a beam with a wavelength different from that of said radiation part corresponding to the other leaf blocks adjacent to corresponding leaf blocks, andsaid image sensors are provided with filters for transilluminating a beam with a wavelength irradiated by a pair of said radiation part. 21. A radiotherapy unit according to claim 17, wherein a plurality of said leaf blocks is arranged in parallel,a plurality of said radiation parts are placed corresponding to each leaf block in pairs,a plurality of said image sensors are placed corresponding to said radiation part in pairs,said radiation part irradiates a beam with a wavelength different from that of said radiation part corresponding to the other leaf blocks adjacent to corresponding leaf blocks, andsaid detection part further comprises an extraction part acquiring images obtained by irradiation of the radiation part by extracting only images created by a beam with a wavelength irradiated by said radiation part paired with the image sensors. 22. A radiotherapy unit comprising:a radiation source for irradiating radiation;a bed on which to place an object; anda multi-leaf collimator between said radiation source and said bed, narrowing a radiation field to a predetermined shape, said multi-leaf collimator comprising:leaf blocks movable in the direction of scaling the radiation field and having a pattern drawn along the direction of movement on a predetermined surface; anda detection part configured to acquire an image of the pattern included in a region along said predetermined surface and to detect displacement of said leaf blocks based on a temporal change of said images. 23. A radiotherapy unit according to claim 22, wherein said pattern has location-specific markings in parallel along a drawing area, andsaid detection part specifies the arranged locations of said pattern according to said location-specific markings. 24. A radiotherapy unit according to claim 22, wherein said detection part comprises:a radiation part irradiating a beam in the direction of said predetermined surface;image sensors subject to light reflected from the direction of said predetermined surface and acquiring said images; anda location acquisition part acquiring the locations of said leaf blocks from pattern images existing in said images. 25. A radiotherapy unit according to claim 24, wherein said location acquisition part comprises:a recognition part recognizing the arranged locations of the pattern existing in said images, wherein,the locations of said leaf blocks are acquired according to locations of said arranged pattern. 26. A radiotherapy unit according to claim 24, wherein a plurality of said leaf blocks is arranged in parallel, andsaid radiation part and said image sensors placed corresponding to predetermined leaf blocks, and said radiation part and said image sensors placed corresponding to the other leaf blocks adjacent to the predetermined leaf blocks, are differently arranged in line at the locations of placement. 27. A radiotherapy unit according to claim 24, wherein a plurality of said leaf blocks is arranged in parallel,a plurality of said radiation parts are placed corresponding to each leaf block in pairs,a plurality of said image sensors are placed corresponding to said radiation part in pairs,said radiation part irradiates a beam with a wavelength different from that of said radiation part corresponding to the other leaf blocks adjacent to corresponding leaf blocks, andsaid image sensors are provided with filters for transilluminating a beam with a wavelength irradiated by a pair of said radiation part. 28. A radiotherapy unit according to claim 24, wherein a plurality of said leaf blocks is arranged in parallel,a plurality of said radiation parts are placed corresponding to each leaf block in pairs,a plurality of said image sensors are placed corresponding to said radiation part in pairs,said radiation part irradiates a beam with a wavelength different from that of said radiation part corresponding to the other leaf blocks adjacent to corresponding leaf blocks, andsaid detection part further comprises an extraction part acquiring images obtained by irradiation of the radiation part by extracting only images created by a beam with a wavelength irradiated by said radiation part paired with the image sensors.