A therapeutic apparatus (100) comprising: a radio therapy apparatus (102) for treating a target zone (146) of a subject (144), wherein the radio therapy apparatus comprises a radio therapy source (110) for generating electromagnetic radiation (114), wherein the radio therapy apparatus is adapted for rotating the radio therapy source about a rotational point (116)； a mechanical actuator (104) for supporting the radio therapy apparatus and for moving the position and/or orientation of the rotational point； and a magnetic resonance imaging system (106) for acquiring magnetic resonance data (170) from an imaging zone (138), wherein the target zone is within the imaging zone, wherein the magnetic resonance imaging system comprises a magnet (122) for generating a magnetic field within the imaging zone, wherein the radio therapy source is adapted for rotating at least partially about the magnet.
