PROBLEM TO BE SOLVED: To improve the calculation accuracy of a dose distribution related to a movable target, in continuous scanning radiation for radiating a particle beam even in radiation position change.SOLUTION: A treatment planning device 501 discretizes a radiation amount in change of a radiation position to which a particle beam is radiated, for calculation, associates a series of 3DCT images included in a 4DCT image with information of lapsed time since start until completion of radiation of a particle beam 300, distributes the discretized radiation amount to the 3DCT images based on the associated series of 3DCT images and information of the lapsed time, calculates a dose distribution of the particle beam 300 on the 3DCT images to which the radiation amount is distributed, calculates corresponding positions among the 3DCT images based on non-rigid registration, and integrates the dose distribution formed for every 3DCT image radiation period for every corresponding position among the 3DCT images over a period since start until completion of radiation of the particle beam 300.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2020,JPO&INPIT【課題】照射位置変更中にも粒子線を照射する連続スキャニング照射において、動く標的に関する線量分布の算出精度を向上させる。【解決手段】治療計画装置５０１は、粒子線が照射される照射位置変更中の照射量を計算用に離散化し、４ＤＣＴ画像に含まれる一連の３ＤＣＴ画像と、粒子線３００の照射の開始から完了までの経過時間の情報とを関連付け、関連付けされた一連の３ＤＣＴ画像と経過時間の情報に基づいて、計算用に離散化された照射量を３ＤＣＴ画像に分配し、照射量が分配された３ＤＣＴ画像上で粒子線３００の線量分布を演算し、非剛体レジストレーションに基づいて、３ＤＣＴ画像間の対応する位置を算出し、３ＤＣＴ画像照射期間ごとに形成される線量分布を、粒子線３００の照射の開始から完了までに渡って３ＤＣＴ画像間の対応する位置ごとに積算する。【選択図】図１
