Patent Number: 
Section: claims

1. A particle beam treatment device in which, when an irradiation target is partitioned along a depth direction thereof into a plurality of slices and a particle beam formed for each of the slices is radiated thereto in a depth order, an energy of the particle beam to be emitted from an accelerator is set for every slice group including two or more adjacent ones of the slices, and an attenuation amount is set for each slice in said slice group,said particle beam treatment device comprising:a variable range shifter that adjusts the attenuation amount by changing a thickness of its transmissive plate through which the particle beam is transmitted;an irradiation nozzle that has a scanning electromagnet and that makes forming of the particle beam adjusted in the attenuation amount, according to each of the slices;a four-pole electromagnet that is placed between the variable range shifter and the irradiation nozzle, and that operates so as to converge the particle beam having been spread by the transmissive plate; anda control unit that determines set values of the accelerator and the variable range shifter, and that controls an amount of magnetic excitation of the four-pole electromagnet according to the set values;wherein, for said every slice group, the control unit sets higher the energy to be emitted from the accelerator than an energy corresponding to the slice at a deepest location in said slice group so that the transmissive plate has a predetermined thickness for the slice at the deepest location; andwherein, with respect to the thickness of the transmissive plate to be set for said every slice group, the thickness set for the slice group at a deep location is larger than or equal to the thickness set for the slice group at a shallow location, and the thickness set for the slice group at a deepest location is thicker than the thickness set for the slice group at a shallowest location. 2. The particle beam treatment device of claim 1, wherein the irradiation nozzle makes said forming in accordance with the slice by a scanning method. 3. The particle beam treatment device of claim 1, wherein a collimator for limiting passing of the particle beam spread out to a predetermined extent or more, is placed between the variable range shifter and the four-pole electromagnet. 4. The particle beam treatment device of claim 2, wherein a collimator for limiting passing of the particle beam spread out to a predetermined extent or more, is placed between the variable range shifter and the four-pole electromagnet. 5. An operation method of a particle beam treatment device, comprising: when an irradiation target is partitioned along a depth direction thereof into a plurality of slices and a particle beam formed by an irradiation nozzle for each of the slices is radiated thereto in a depth order,setting an energy of the particle beam to be emitted from an accelerator for every slice group including two or more adjacent ones of the slices;setting an attenuation amount for each slice in said slice group, by a variable range shifter; andconverging the particle beam incident to the irradiation nozzle, by a four-pole electromagnet placed between the variable range shifter and the irradiation nozzle;wherein, for said every slice group, a set value of the energy of the accelerator is set higher than an energy corresponding to the slice at a deepest location in said slice group so that the variable range shifter has a predetermined attenuation amount for the slice at the deepest location;wherein, with respect to the attenuation amount to be set for said every slice group, the amount set for the slice group at a deep location is larger than or equal to the amount set for the slice group at a shallow location, and the amount set for the slice group at a deepest location is larger than the amount set for the slice group at a shallowest location; andwherein an amount of magnetic excitation of the four-pole electromagnet is controlled according to the set value of the energy of the accelerator and the attenuation amount by the variable range shifter.