The objective is to obtain a bolus, with which there can be formed an irradiation field that is accurately suited to the depth-direction shape of an irradiation subject, and a particle beam therapy system. An irradiation orbit (TB) of a particle beam (B) is defined by a first slant (α) with respect to a first axis (Asa) that starts from a first reference point (CPa), that is perpendicular to a beam axis (XB), and that includes the first reference point (CPa) and by a second slant (β) with respect to a second axis (Asb) that is perpendicular to the beam axis (XB) and the first axis (Asa) the shape of a bolus (6) is set in such a way that the path length (LB), of a particle beam(B), within the bolus (6) in each of the irradiation orbits (TB) defined for combinations within a predetermined range among combinations of the first slant (α) and the second slant (β), compensates the path length (LK) from a body surface (fk) to a to-be-irradiated portion (IS).本發明之目的為獲得一種膠塊土及粒子束治療裝置,該膠塊土可以正確地成形在適於照射對象的深度方向形狀的照射場。本發明係將第一基準點(CPa)當作起點,藉由第一傾斜度(α)與第二傾斜度(β)來定義粒子束(B)的照射軌道(TB),該第一傾斜度(α)係以對於射束軸(XB)成垂直且包含以第一基準點(CPa)的第一軸(Asa)當作中心,該第二傾斜度(β)則以對於射束軸(XB)及第一軸(Asa)成垂直之第二軸(Asb)當作中心,並且對預定的第一傾斜度(α)與第二傾斜度(β)的複數個組合來設定膠塊土(6)的形狀,俾使分別定義的照射軌道(TB)中膠塊土(6)內的路徑長度(LB),得以補償從身體表面(fK)到被照射部(IS)為止的路徑長度(LK)。6...膠塊土Asa...上游掃描電磁鐵的掃描軸(第一軸)Asb...下游掃描電磁鐵的掃描軸(第二軸)B...帶電粒子射束CPa...第一基準點CPb...第二基準點fK...身體表面LB...膠塊土內的路徑長度LK...到被照射部為止的路徑長度(體內深度)IS...患部P...目標照射位置TB...照射軌道XB...粒子射束之射束軸αp...角度
