PROBLEM TO BE SOLVED: To create a preferable therapy plan in a short period of time, in which a gap between a particle beam irradiation nozzle and a patient is suppressed to a permissible value or less.SOLUTION: Presence and absence of interference is checked starting from a position where a three-dimensional model of an irradiation nozzle is initially disposed. When no interference is determined in the immediately before the check, the position of the three-dimensional model of the irradiation nozzle is moved by a preset travel width in a direction of approaching an isocenter, and when the presence of interference is determined, the position thereof is moved by the preset travel width in a direction of separating from the isocenter. This movement is repeated until a gap becomes a permissible value or less. A travel width used in moving in the approaching direction after the presence of interference is determined is set to a smaller value than a travel width used in moving in the immediately before separating direction.COPYRIGHT: (C)2014,JPO&INPIT【課題】ギャップを許容値以下に抑えた好適な治療計画を短時間に作成できるようにする。【解決手段】照射ノズルの立体形状モデルを初期位置に配置したところから干渉の有無のチェックを開始し、直前のチェックで干渉が無いと判定された場合はアイソセンタに近接する方向に、干渉が有ると判定された場合はアイソセンタから離反する方向に、照射ノズルの立体形状モデルの位置を設定された移動幅で移動させる、ことをギャップが許容値以下になるまで繰り返すとともに、干渉が有ると判定された後の近接する方向への移動に用いる移動幅を、直前の離反する方向の移動に用いた移動幅よりも小さい値に設定する。【選択図】図1
