Patent Number: 
Section: abstract

Disclosed is a medical particle irradiation apparatus comprising a rotating gantry 1 including an irradiation unit 4 emitting particle beams; an annular frame 16 located within and supported by the rotating gantry 1 such that it can rotate relative to the rotating gantry 1; an annular frame 15 fixedly located opposite the annular frame 16; an anti-corotation mechanism 34 being in contact with both the annular frames 16 and 15 to prevent the annular frame 16 from rotating together with the rotating gantry 1 during rotation of the rotating gantry 1; and a flexible moving floor 17 interposed between the annular frames 15 and 16, the flexible moving floor 17 being engaged with the annular frames 15 and 16 in such a manner as to move freely such that its bottom is substantially level and that it moves as the rotating gantry rotates.