A particle therapy apparatus (1) for irradiating a target (5) with a charged particle beam (2) and comprising a particle accelerator and an isocentric gantry (10) rotatable about an axis Y. The gantry (10) comprises a sequence of bending magnets to successively bend and finally direct the particle beam (2) towards the isocentre (20) of the gantry (10). A last bending magnet (15) of said sequence is configured to bend the particle beam (2) in a first plane P1 comprising the isocentre (20) and making a large angle with the axis Y. The gantry (10) also comprises a first scanning magnet (31) arranged upstream of the last bending magnet (15) and configured to scan the particle beam (2) over the target (5) in the first plane P1. The apparatus also comprises a magnetic resonance imaging (MRI) system having two main magnet units (41, 42) arranged on both sides of the isocentre (20) and configured to generate a main magnetic field (Bo) which is parallel to or coaxial with the axis Y. MRI imaging of the target (5) at the isocentre (20) can hence be achieved while or while not scanning the particle beam (2) over the target (5).
