PROBLEM TO BE SOLVED: To provide a treatment planning device for determining optimum beam intensity for irradiation in which discrete spot irradiation and continuous beam irradiation are mixed, and an ion beam radiotherapy system.SOLUTION: In a treatment planning device and an ion beam radiotherapy system, the treatment planning device includes: a spot determination part 1 which divides an irradiated region for being irradiated with a charged particle beam into a plurality of layers in a travelling direction of the charged particle beam, and which arranges a plurality of irradiation spots serving as charged particle beam irradiation positions, in the layer and a beam intensity determination part 2 which determines beam intensity of each layer by evaluating irradiation time by varying the beam intensity within the scope of preset conditions of variations in dose distribution.SELECTED DRAWING: Figure 1【課題】治離散スポット照射と連続ビーム照射が混在する照射における最適なビーム強度を決定するための療計画装置および粒子線治療システムを提供する。【解決手段】荷電粒子ビームを照射する照射領域を、前記荷電粒子ビームの進行方向に複数の層に分割して、前記層に、前記荷電粒子ビームの照射位置となる複数の照射スポットを配置するスポット決定部1と、予め設定された線量分布変化の条件の範囲でビーム強度を変化させて照射時間を評価し、前記層毎のビーム強度を決定するビーム強度決定部2を備えた療計画装置および粒子線治療システムである。【選択図】図1
