Pneumatic stepper motor and device comprising at least one such pneumatic stepper motor

The invention relates to a pneumatic stepper motor, comprising: - a housing, said housing accommodating at least part of: - a rack or geared axle comprising a plurality of gear elements; and - two pistons, each comprising at least two teeth, said pistons being arranged to cooperate with said rack or geared axle. The racks may either be straight or curved. The pistons are preferably double-acting pistons. The invention also relates to a device, comprising at least one, and preferably a plurality of, such pneumatic stepper motor (s). The device may in particular be an MRI-compatible robotic system, more in particular for example an MRI-guided breast biopsy device.