Particle therapy system

A particle therapy system is disclosed, including a treatment chamber and a rotatable gantry with a radiation treatment unit, capable of emitting particles at a variety of angles. A movably supported floor is provided in the treatment chamber, capable of being rotated about the same axis as the gantry, and an imaging modality is disposed on a surface of the movably supported floor. The movably supported floor supports the weight of the imaging modality and is configured so that the imaging modality may be placed in a parked position when the gantry is being rotated. The imaging modality may be a C-arm X-ray device positionable by a robot.