PROBLEM TO BE SOLVED: To improve accuracy, determine the position of an irradiated object quickly, and reduce X-ray exposure dose by adopting six axes of displacement calculation for positioning.SOLUTION: A positioning device for a radiation beam irradiated object 2 includes a first display section for displaying previous first and second images and present first and second projection images taken from first and second directions of a previous and present irradiated object K, a first calculation section for acquiring previous and present lines in the previous and present second projection images by means of previous and present first index points designated by feature points of the irradiated object K in the previous and present first projection images, a second display section for displaying the previous and present lines in the previous and present second projection images, a second calculation section for calculating the position of the present and previous feature points by means of previous and present second index points designated as feature points on previous and present lines g2 and g2 displayed on the previous and present second projection images and by means of the previous and present first index points, a third calculation section for calculating positional displacement between the previous and present positions of the irradiated object K by calculating positional displacement between the previous and present feature points, and an output section for outputting the positional displacement.COPYRIGHT: (C)2012,JPO&INPIT【課題】位置決めのずれ量算出数が6軸となり精度が向上し、照射対象の位置の決定に時間かからず、X線の被曝量が少ない。【解決手段】放射線ビーム照射対象位置決め装置2は、前・今回の照射対象Kの第1・第2方向からの前・今回の第1・第2投影画像を表示する第1表示部と、前・今回の第1投影画像で照射対象Kの特徴点として指示される前・今回の第1指示点によって、前・今回の第2投影画像での前・今回の直線を求める第1演算部と、前・今回の直線を前・今回の第2投影画像に表示する第2表示部と、前・今回の第2投影画像に表示された前・今回の直線g2、g2´上に特徴点として指示される前・今回の第2指示点と、前・今回の第1指示点とから、前・今回の特徴点の位置を演算する第2演算部と、前・今回の特徴点の間の位置ずれ量を演算し、照射対象Kの前・今回の位置の位置ずれ量を演算する第3演算部と、該位置ずれ量を出力する出力部とを備える。【選択図】図4
