A medical device is configured for diagnosis or treatment of a tissue within a body. The medical device comprises an elongate member and a position sensor. The elongate member is configured to be received within the body, and has a lumen extending between a proximal end and a distal end. The position sensor is disposed within the lumen proximate the distal end of the deformable member. The position sensor comprises a coil wound to form a central passage and configured to generate a current flow when subject to a magnetic field, and a high-permeability antenna having at least a portion disposed outside the central passage to concentrate the magnetic field into the coil and increase the current flow.
