A medical-device magnetic guiding position detecting system that can prevent a decrease in the strength of a position detecting magnetic field in an operating area of a medical device is provided. The snapshot data is copy of the directory system at a time in the past. The second pixel electrode electrically connected to the second active device is electrically insulated from the first pixel electrode and separates the first and the second electrode block. An inflatable or expandable member may be provided near a distal tip of the catheter to prevent release of dislodged thrombus.