Surgical robots and especially their subclass of image-guided systems require special design, construction and control compared to industrial types, due to the special requirements of the medical and imaging environments. Imager compatibility raises significant engineering challenges for the development of robotic manipulators with respect to imager access, safety, ergonomics, and above all the non-interference with the functionality of the imager. These apply to all known medical imaging types, but are especially challenging for achieving compatibility with the class of Magnetic Resonance Imaging (MRI) systems. Even though a large majority of robotic components may be redesigned to be constructed of MRI compatible materials, for other components such as the motors used in actuation, prescribing MRI compatible materials alone is not sufficient. The electromagnetic motors most commonly used in robotic actuation, for example, are incompatible by principle. We report here an important achievement in MRI instrumentation, a new type of pneumatic motor, PneuStep, specifically developed for MrBot, the first pneumatic, fully actuated MR robotic system that can be located within the scanner alongside the patient and operating under remote control based on the images.