Abstract: A hydraulic system for a mobile vehicle that supports and positions a load relative to a docking structure, such as a patient relative to a medical diagnostic apparatus. The mobile vehicle includes a wheeled base, a carriage on the base, a hydraulic cylinder for raising and lowering the carriage relative to the base, a load supporting cradle slidably mounted on the carriage for movement in a longitudinal direction between an operative extended position and an inoperative retracted position on the carriage, and a hydraulic system for controlling the operation of the vehicle and its components. The vehicle includes co-operating members on the base and on the docking structure for properly aligning and positioning the vehicle with respect to the docking structure. The movement of the carriage may be accomplished either manually through a foot pump or through a hydraulic power interlock between the vehicle base and docking structure which is engageable upon docking.