The invention relates to a preparing apparatus for preparing an influencing procedure for influencing a subject. The preparing apparatus (1) comprises a subject coil (3) for generating a magnetic resonance image of he subject (7), an instrument guide device (5) for guiding an instrument (6) for influencing the subject (7), a marker (9) being visible in the magnetic resonance image, and an attaching element for attaching the instrument guide device (5) to the subject coil (3) in a known spatial relationship. Since the spatial relationship between the instrument guide device (5) and the subject coil (3) is known, if they are attached to each other, a time consuming registration procedure for registering an influence trajectory, which has been planned based on the magnetic resonance image, and the instrument guide device (5) can be avoided.