Method of scaling navigation signals to account for impedance drift in tissue
AssigneeSt. Jude Medical, Atrial Fibrillation Division, Inc.
InventorJohn A. Hauck
Life of this patent
Estimating the term…
Abstract
A method for scaling the impedance measured during the course of an electrophysiology study accounts for impedance drifts. By scaling the impedance there is greater assurance that previously recorded positional information can be used to accurately relocate an electrode at a prior visited position. The scale factor may be based upon a mean value across several sensing electrodes. Alternatively, the scale factor may be calculated specifically with respect to an orientation of a dipole pair of driven electrodes.
Claims13
An apparatus for use in generating an electric field across a patient's body during an electrophysiology study, comprising:
- a computer system having a plurality of inputs configured to be coupled to a plurality of surface electrodes, wherein the computer system comprises at least one processor programmed to:
- drive at least one pair of the plurality of surface electrodes to create an electrical field across the patient's body;
- measure at least one biologic impedance encountered by the electrical field with respect to at least one undriven surface electrode of the plurality of surface electrodes;
- calculate a mean absolute value of the measured at least one biologic impedance as a function of time, Pm(t);
- save an initial calculated mean absolute value of the measured at least one biologic impedance, Pa;
- and
- multiply an impedance measurement between a measurement electrode and a reference electrode by a ratio, Pa/Pm(t), to compute a scaled impedance.
A tangible computer-readable medium having computer-executable instructions for performing steps comprising:
- saving at least one biologic impedance measurement encountered by at least one sensing electrode on a surface of a patient's body under influence of a dipole-driven electric field;
- calculating a mean absolute value of the measured at least one biologic impedance continuously as a function of time, Pm(t);
- saving an initial calculated mean absolute value of the measured at least one biologic impedance, Pa;
- multiplying an impedance measurement between a measurement electrode and a reference electrode by a ratio, Pa/Pm(t), to compute a scaled impedance;
- and
- determining a location of the measurement electrode within the dipole-driven electric field based upon the scaled impedance.
An electrophysiology system, comprising:
- a plurality of surface electrodes;
- a measurement electrode;
- a reference electrode;
- and
- a computer system operably coupled to the plurality of surface electrodes, the measurement electrode, and the reference electrode, wherein the computer system comprises at least one processor that:
- drives at least one pair of the plurality of surface electrodes to create an electrical field across the patient's body;
- measures at least one biologic impedance encountered by the electrical field with respect to at least one undriven surface electrode of the plurality of surface electrodes;
- calculates a mean absolute value of the measured at least one biologic impedance as a function of time, Pm(t);
- saves an initial calculated mean absolute value of the measured at least one biologic impedance, Pa;
- and
- multiplies an impedance measurement between the measurement electrode and the reference electrode by a ratio, Pa/Pm(t), to compute a scaled impedance.
A method of determining a position of a measurement electrode within a patient's body, the method comprising:
- positioning a plurality of surface electrodes on a surface of the patient's body;
- positioning the measurement electrode within the patient's body;
- operably connecting the plurality of surface electrodes to a computer system having at least one processor;
- and
- operating the computer system to:
- drive at least one pair of the plurality of surface electrodes to create an electrical field across the patient's body;
- measure at least one biologic impedance encountered by the electrical field with respect to at least one undriven surface electrode of the plurality of surface electrodes;
- calculate a mean absolute value of the measured at least one biologic impedance as a function of time, Pm(t);
- save an initial calculated mean absolute value of the measured at least one biologic impedance, Pa;
- measure an impedance between the measurement electrode and a reference electrode;
- multiply the impedance measured between the measurement electrode and the reference electrode by a ratio, Pa/Pm(t), to compute a scaled impedance;
- and
- determine a location of the measurement electrode within the patient's body based on the scaled impedance.
Dependencies are inferred from the claim text.