Patent Number: 
Section: claims

1. A particle beam irradiation apparatus that irradiates a target and limits unnecessary irradiation onto normal tissue without the use of a scatterer, bolus and collimator, said particle beam irradiation apparatus (i) being mounted in a rotating gantry for rotating an irradiation direction of a charged particle beam accelerated by an accelerator and (ii) comprising:a columnar-irradiation-field generation apparatus that generates a columnar irradiation field by enlarging the Bragg peak of the charged particle beam and includes (i) a plurality of absorbers, each absorber having a uniform thickness and reducing the energy of the charged particle beam in accordance with the thickness thereof through which the charged particle beam passes, (ii) a plurality of driving devices, each driving device configured to drive a respective absorber from the plurality of absorbers, and (iii) a change control apparatus for driving the driving devices;a scanning irradiation system positioned at a downstream side of the columnar-irradiation-field generation apparatus and that includes an X-direction scanning electromagnet that scans the charged particle beam in the X-direction and a Y-direction scanning electromagnet that scans the charged particle beam in the Y-direction; anda pair of position monitors that are positioned at a downstream side with respect to both the columnar-irradiation-field generation apparatus and the scanning irradiation system and that detect a passing position of the charged particle beam,wherein a uniform thickness of one absorber from the plurality of absorbers of the columnar-irradiation-field generation apparatus differs from the uniform thickness of another absorber from the plurality of absorbers,wherein the change control apparatus of the columnar-irradiation-field generation apparatus drives the driving devices so as to control the combined thickness of the plurality absorbers through which the charged particle beam passes, andwherein the columnar-irradiation-field generation apparatus generates the columnar irradiation field such that the enlarged Bragg peak is a Spread-Out-Bragg-Peak (SOBP) width, and the SOBP width has a depth in the direction of the charged particle beam that is larger than the cross-sectional dimension of the columnar irradiation field in an X-Y direction that is perpendicular to the charged particle beam. 2. The particle beam irradiation apparatus of claim 1, wherein each absorber from the plurality of absorbers is configured to be positioned along a beam axis of the charged particle beam such that each absorber from the plurality of absorbers is in alignment with the charged particle beam. 3. The particle beam irradiation apparatus of claim 1, wherein the change control apparatus is configured to drive the driving devices such that at least two absorbers from the plurality of absorbers are positioned along a beam axis of the charged particle beam such that the at least two absorbers from the plurality of absorbers are in alignment with the charged particle beam. 4. The particle beam irradiation apparatus of claim 1, wherein the columnar-irradiation-field generation apparatus further includes a depth-direction irradiation field enlargement apparatus for enlarging the Bragg peak of the charged particle beam, wherein said depth-direction irradiation field enlargement apparatus is positioned at a downstream side of the plurality of absorbers. 5. The particle beam irradiation apparatus of claim 4, wherein the depth-direction irradiation field enlargement apparatus includes:a ridge filter having a thickness distribution in which energy loss of the charged particle beam differs depending on the position thereon through which the charged particle beam passes;a pair of upstream deflection electromagnets that move the passing position, of the charged particle beam in the ridge filter;a pair of downstream deflection electromagnets that return the orbit of the charged particle beam toward a beam axis along which the charged particle beam has entered the depth-direction irradiation field enlargement apparatus; andan irradiation-field enlargement control apparatus that controls the pair of upstream deflection electromagnets and the pair of downstream deflection electromagnets in such a way that the charged particle beam passes through a predetermined thickness distribution of the ridge filter. 6. A particle beam irradiation apparatus that irradiates a target and limits unnecessary irradiation onto normal tissue without the use of a scatterer, bolus and collimator, said particle beam irradiation apparatus (i) being mounted in a rotating gantry for rotating an irradiation direction of a charged particle beam accelerated by an accelerator and (ii) comprising:a columnar-irradiation-field generation apparatus that generates a columnar irradiation field by enlarging the Bragg peak of the charged particle beam and includes (i) a plurality of absorbers, each absorber having a uniform thickness, (ii) a plurality of driving devices, each driving device configured to drive a respective absorber from the plurality of absorbers, and (iii) a depth-direction irradiation field enlargement apparatus positioned at a downstream side of the plurality of absorbers;a scanning irradiation system positioned at a downstream side of the columnar-irradiation-field generation apparatus and that includes an X-direction scanning electromagnet that scans the charged particle beam in the X-direction and a Y-direction scanning electromagnet that scans the charged particle beam in the Y-direction; anda pair of position monitors that are positioned at a downstream side with respect to both the columnar-irradiation-field generation apparatus and the scanning irradiation system and that detect a passing position of the charged particle beam,wherein a uniform thickness of one absorber from the plurality of absorbers of the columnar-irradiation-field generation apparatus differs from the uniform thickness of another absorber from the plurality of absorbers,wherein a change control apparatus drives the driving devices of the columnar-irradiation-field generation apparatus so as to control the combined thickness of the plurality absorbers through which the charged particle beam passes, andwherein the columnar-irradiation-field generation apparatus generates the columnar irradiation field such that the enlarged Bragg peak is a Spread-Out-Bragg-Peak (SOBP) width, and the SOBP width has a depth in the direction of the charged particle beam that is larger than the cross-sectional dimension of the columnar irradiation field in an X-Y direction that is perpendicular to the charged particle beam. 7. The particle beam irradiation apparatus of claim 1,wherein the columnar-irradiation-field generation apparatus is configured to generate (i) an outer columnar irradiation field having a first SOBP width, and (ii) an inner columnar irradiation field having a second SOBP width, which is different from the first SOBP width, andwherein the scanning irradiation system performs irradiation while scanning the outer columnar irradiation field generated by the columnar-irradiation-field generation apparatus in accordance with the distal form of the irradiation subject, and subsequently performs irradiation while scanning the inner columnar irradiation field inside the irradiation subject, relative to the outer columnar irradiation field. 8. The particle beam irradiation apparatus of claim 6,wherein the columnar-irradiation-field generation apparatus is configured to generate (i) an outer columnar irradiation field having a first SOBP width, and (ii) an inner columnar irradiation field having a second SOBP width, which is different from the first SOBP width, andwherein the scanning irradiation system performs irradiation while scanning the outer columnar irradiation field generated by the columnar-irradiation-field generation apparatus in accordance with the distal form of the irradiation subject, and subsequently performs irradiation while scanning the inner columnar irradiation field inside the irradiation subject, relative to the outer columnar irradiation field.