A medical system includes first and second medical probes in an arrangement and configured for insertion into a lumen or vessel of a patient, the first medical probe having indicia, and a detector is fixedly coupled to the second medical probe and configured for insertion into and advancement through the lumen or vessel along with the second medical probe, wherein the detector detects passage of the indicia as the first and second medical probes are moved relative to each other within the lumen or body vessel. An electromechanical driver is coupled to, and operable to move the first and second medical probes. A system controller is configured for directing the electromechanical driver to move the first and second medical probes relative to each other within the lumen or body vessel based on signals received from the detector when the detector is positioned within the lumen or body vessel.
