PROBLEM TO BE SOLVED: To solve the problem of excess irradiation in IMRT by a particle beam therapy apparatus by raising the irradiation flexibility in the depth direction, without utilizing a bolus.SOLUTION: A particle beam irradiation apparatus 58 has a scanning irradiation system 34 and a columnar irradiation field generation apparatus 4 which generates a columnar irradiation field and is mounted in a rotating gantry for rotating the irradiation direction of a charged particle beam 1. The columnar irradiation field generation apparatus generates according to the distal shape of an irradiation object an outer columnar irradiation field which is a columnar irradiation field having one SOBP width, and an inner columnar irradiation field, inside the irradiation object, which is a columnar irradiation field having another SOBP width different from the one for the outer columnar irradiation field. The scanning irradiation system scans and irradiates the outer columnar irradiation field according to the distal shape of the irradiation object in a spread-all-over fashion, and scans and irradiates the inner columnar irradiation field as if spreading the inner irradiation field all over the inside of the outer irradiation field.COPYRIGHT: (C)2015,JPO&INPIT【課題】ボーラスを用いることなく深さ方向への照射自由度を上げることにより、粒子線治療装置におけるIMRTの過照射問題を解決することを目的とする。【解決手段】走査照射系34と柱状の照射野を生成する柱状照射野生成装置4を備え、荷電粒子ビーム1の照射方向を回転させる回転ガントリに搭載された粒子線照射装置58であって、柱状照射野生成装置は、照射対象のディスタル形状に応じて、一つのSOBPの幅を有する柱状の照射野である外側柱状照射野と、照射対象の内側に外側柱状照射野と異なる他のSOBPの幅を有する柱状の照射野である内側柱状照射野とを生成し、走査照射系は、外側柱状照射野を照射対象のディスタル形状に合わせて敷き詰めるように走査して照射し、内側柱状照射野を外側柱状照射野の内側に敷き詰めるように走査して照射する。【選択図】図1
