A therapeutic apparatus comprising:a magnetic resonance imaging system adapted for acquiring a set of magnetic resonance imaging data in an imaging zone, wherein the magnetic resonance imaging system comprises a means for generating a magnetic field,a guiding means adapted for guiding a beam of charged particles to a target zone within a subject such that the beam encloses an angle with the magnetic field lines of the magnetic field within the imaging zone, the angle being between 0 degrees and 30 degrees, wherein the imaging zone comprises the target zone,a zone determination means for determining the location of the target zone within the subject using the set of magnetic resonance imaging data.
