A guidewire, consisting of a hollow tube, containing a longitudinal lumen and having a spiral channel cut into the tube, and having a distal end. The guidewire has an elongate flexible core positioned within the longitudinal lumen. The guidewire also has a conductive coil, wound around the core at a location within the lumen in proximity to the distal end, that is coupled to output a signal in response to a magnetic field applied to the guidewire.
