The present disclosure relates to a particle therapy apparatus for irradiating a target with a charged particle beam. In one implementation, the apparatus includes an isocentric gantry rotatable about an axis and configured to direct a particle beam towards an isocenter of gantry and according to a final beam direction, a magnetic resonance imaging system configured to generate a main magnetic field parallel to the final beam direction, and a passive magnetic shield surrounding the magnetic resonance imaging system, the passive magnetic shield and the magnetic resonance imaging system being synchronously rotatable with the gantry about the axis.
