| 摘要 |
An charged particle beam irradiation apparatus is provided which increases the width in a depth direction of a Bragg peak to be formed, by means of a simple construction. The charged particle beam irradiation apparatus includes a charged particle beam generation device and an irradiation field forming device. The charged particle beam generation device has a front accelerator and a synchrotron. An ion beam is guided to the irradiation field forming device from the synchrotron. The irradiation field forming device has a beam enlarging device, a Bragg peak enlarging device and a ridge filter. A pair of filter elements which constitute the Bragg peak enlarging device have a plurality of stick-shaped portions spaced apart from one another. The filter elements are disposed with their respective stick-shaped portions partly superposed to extend in mutually different directions. An ion beam that has passed through the Bragg peak enlarging device contains three ion beam components having different energies produced according to the difference between passed positions of each of the filter elements, whereby the width of a Bragg peak formed in the body of a patient is increased.
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