Apparatus for radiotherapy of a patient, comprising: a radiation treatment room that is protected against radiation and has an opening that includes a door arrangement protected against radiation operable to close the opening； a patient support table； a magnetic resonance imaging system to acquire MR images of a volume of imaging that includes the patient's target location； including the imaging system: an actionable MRI magnet to generate a magnetic field that will be applied to the patient, the magnet having a cylindrical orifice to surround the patient's target location； an RF transmission coil arrangement for generating an RF pulse in a transmission phase that will be applied to the subject from which images are to be obtained, so that the subject generates an RM signal in response to the magnetic field and pulse of RF applied； a reception coil arrangement for acquiring the RM signal in a reception phase； and a signal processing system to receive the RM signal to carry out the signal processing by which an image is generated； a treatment apparatus for applying radiotherapy to a target location in the patient on the support table； the patient support table and the treatment apparatus being mounted in said radiation treatment room, the RM magnet being mounted for movement from an external position of the radiation-protected door arrangement inside the opening to a Imaging position for cooperation with the patient on the patient support table for MR imaging； the RM magnet being mounted for movement from the imaging position to the outer position for radiation treatment of the patient on the patient support table； wherein an arrangement is provided to prevent RF signals from the treatment apparatus from interfering with the MR imaging system during imaging on the patient support table； and in which both the patient support table and the treatment apparatus are arranged to remain in a treatment location in the radiation treatment room when the magnet moves to the ima
