A flexible catheter (10) includes an elongated body (50), and a sensor (58). The elongated body has proximal and distal end portions (52, 54) and defines a working channel (56) therethrough. The sensor is disposed in the distal end portion of the elongated body and is adapted for detecting the position of a distal end of the elongated body within the anatomy of a patient. The sensor is formed from a wire (71) that forms a first layer of wraps (72) about the distal end portion of the elongated body and that includes first and second leads (76a, 76b) that form a twisted pair proximal to the first layer of wraps. The twisted pair of the first and second leads extends to the proximal end portion of the elongated body.
