A system comprising a catheter (12) having an expandable element (18), which when expanded, has an annular shape surrounding a passageway. The expandable element in the expanded state is rollable along at least a portion of the shaft of the catheter without slipping. The system may be used for delivering an object to a site in the body, retrieving an object from a body, removing debris and/or other particulate matter from a blood vessel, and distending and/or expanding a pathologically-involved region of a blood vessel wall.