Patient positioning device and patient positioning method

A patient positioning device for positioning a couch supporting a patient to which a charged particle beam is irradiated from a particle beam irradiation system, said patient positioning device comprising:

• an X-ray emission device;
• an image information generator for generating second image information regarding a portion of the patient lying across the path of said charged particle beam by using a signal depending on the X-ray emitted from said X-ray emission device;
• and
• a processing unit for setting, with respect to a first image information which serves as a reference image prepared beforehand based on image data of a tumor in the body of the patient and including an isocenter, a first set area smaller than an area of said first image information and including said isocenter, setting, with respect to the second image information, a second set area smaller than an area of said second image information and having substantially the same size as said first set area and including a position corresponding to the path of said charged particle beam, executing primary pattern matching between the first image information in said first set area and the second image information in said second set area by moving said second set area within said area of said second image information to determine a primary matching area having said second image information most similar to said first image information in said first set area, and executing secondary pattern matching comparing the first image information in said first set area and the second image information in said primary matching area by moving the second image information in said primary matching area relative to the first image information in said first set area, thereby producing information used for positioning of said couch based on a positional offset between said second image information in said second set area before executing said primary pattern matching and said second image information in said primary matching area determined by said primary pattern matching and a positional offset between said second image information in said primary matching area determined by said primary pattern matching and said second image information in said primary matching area provided by said secondary pattern matching.