The present invention relates to an apparatus (100) for moving a target element (60, 70), which comprises a magnetic material (62, 72) and an active agent (61, 71), through an object, placing said target element (60, 70) at a predetermined position within the object and activating the active agent (61, 71), which apparatus (100) comprises:—selection means comprising a selection field signal generator unit (110) and selection field elements (116), in particular selection field magnets or coils, for generating a magnetic selection field (50) having a pattern in space of its magnetic field strength such that a first sub-zone (52) having a low magnetic field strength and a second sub-zone (54) having a higher magnetic field strength are formed in a field of view (28),—drive means comprising a drive field signal generator unit (130) and drive field coils (136a, 136b, 136c) for changing the position in space of the two sub-zones (52, 54) in the field of view (28) by means of a magnetic drive field so that the magnetization of the magnetic material (62, 72) changes locally, and—control means (150) for controlling said signal generator units (110, 130) to generate and provide control currents to the respective field coils to generate appropriate magnetic fields for moving the target element (60, 70) through the object in a direction instructed by movement commands, for placing the target element (60, 70) at the desired position within the object and for activating the active agent (61, 71) when the target element (60, 70) has reached said desired position.
