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Abstract

A system and method for tracking the position and orientation of a probe such as a catheter whose transverse inner dimension may be at most about two millimeters. Three planar antennas that at least partly overlap are used to transmit electromagnetic radiation simultaneously, with the radiation transmitted by each antenna having its own spectrum. In the case of single-frequency spectra, the antennas are provided with mechanisms for decoupling them from each other. A receiver inside the probe includes sensors of the three components of the transmitted field, with sensors for at least two of the three components being pairs of sensors, such as coils, disposed symmetrically with respect to a common reference point. In one variant of the receiver, the coils are collinear and are wound about cores that are mounted in pairs of diametrically opposed apertures in the housing of the probe. In another variant of the receiver-catheter combination, the catheter is configured with an inner and outer sleeve connected at their ends by one or more flexible elements on which the coils are mounted. Each member of a pair of coils that sense the same component of the transmitted field is connected to a different input of a differential amplifier. The position and orientation of the receiver relative to the antennas are determined noniteratively, by setting up an overdetermined set of linear equations that relates the received signals to transmitter-receiver amplitudes, solving for the amplitudes and inferring the position coordinates and the orientation angles of the receiver relative to the transmitter from these amplitudes. For the purpose of navigating the probe within the body of a patient, the antennas are rigidly attached to an imaging device such as a fluoroscope, to provide a common frame of reference for both the acquired images of the patient and the measured position and orientation of the receiver. Alternatively, a second receiver is rigidly attached to the imaging device to provide the common frame of reference. In a third alternative, a third receiver is rigidly attached to the patient during imaging, and the mutual positions and orientations of the patient and the imaging device thus measured are used in subsequent navigation of the probe within the body of the patient. An imaging device that includes an electrically conductive surface is provided with a magnetically permeable compensator for minimizing distortion of the transmitted field. A scheme is provided for retrofitting an apparatus such as the receiver to a prior art catheter.

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First Claim