In a MRI system housed within a room there is provided a movable magnet and additional components for other procedures on the patient, a control system is provided for the relative movement of the magnet and components. This includes a plurality of magnetic field sensors mounted on the components for measuring the magnetic field at the location of the component and an optional camera positioning system so that the control system can estimate relative positions of the components relative to the magnet from the sensed field strengths from the set of sensors to avoid collisions during the movements.