Mutual crosstalk elimination in medical systems using radiator coils and magnetic fields

• US 6,498,477 B1
• Filed: 10/31/2000
• Issued: 12/24/2002
• Est. Priority Date: 03/19/1999
• Status: Expired due to Term

• Current Assignee: Biosense, Inc. (Cardinal Health, Inc.)
• Original Assignee: Biosense, Inc. (Cardinal Health, Inc.)
• Inventors: Govari, Assaf, Fried, Shlomo
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Aurora, Reena
• Application Number:
  US09/702,974
• Time in Patent Office: 784 Days
• Field of Search: 324/207.12, 324/207.17, 324/219, 324/220, 324/222, 324/225, 324/228, 324/229, 324/232, 324/233, 324/236-243, 324/260, 342/417, 342/418, 702/150
• US Class Current: 324/207.12
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 5/062 using magnetic field
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence

Abstract

Apparatus for generating magnetic fields includes a plurality of radiator coils. Driver circuitry drives the coils so as to generate magnetic fields at a plurality of driving frequencies. Each of the coils is driven by a respective current that comprises a basic current at a respective one of the driving frequencies and cancellation currents at one or more of the other driving frequencies, so that each of the radiator coils generates a field substantially only at the respective driving frequency.

Claims

1. Apparatus for generating magnetic fields, comprising:

a plurality of radiator coils; and

driver circuitry, coupled thereto, which drives the coils so as to generate magnetic fields at a plurality of driving frequencies, such that each of the coils is driven by a respective current that comprises a basic current at a respective one of the driving frequencies and cancellation currents at one or more of the other driving frequencies, so that each of the radiator coils generates a field substantially only at the respective driving frequency, wherein the cancellation currents are determined so as to substantially cancel parasitic magnetic fields generated by each of the coils in response to the magnetic fields generated by the other coils at the respective driving frequencies of the other coils.

2. Apparatus in accordance with claim 1, wherein the cancellation currents are generated by the driver circuitry so as to be, in each of the coils, approximately equal in amplitude and opposite in phase to parasitic currents generated in the coil due to the magnetic fields generated by the other coils at the respective driving frequencies of the other coils.

3. Apparatus in accordance with claim 1, wherein the driver circuitry comprises a current analyzer, which is coupled to measure parasitic currents flowing in each of the coils at the respective driving frequencies of the other coils, and wherein the driver circuitry is adapted to generate the cancellation currents responsive to the measured parasitic currents.

4. Apparatus in accordance with claim 3, wherein the driver circuitry comprises an adaptive current supply, which is driven by the current analyzer to generate the cancellation currents.

5. Apparatus in accordance with claim 3, wherein the driver circuitry comprises a memory, which is adapted to store, for each of the coils, data indicative of a waveform of the respective current with which the coil is to be driven, and wherein the data are modified responsive to the measured parasitic currents.

6. Apparatus in accordance with claim 3, wherein the driver circuitry is adapted to adjust the generated respective current in each coil so as to minimize the parasitic electrical current measured therein.

7. A method for generating a magnetic field having a desired narrow frequency band, comprising:

driving a radiator coil with an electrical current at a frequency in the desired narrow frequency band;

analyzing the current flowing in the coil to measure induced current components at one or more undesired frequencies caused by at least one other radiator coil; and

adjusting the current driving the coil so as to include correction current components at the one or more undesired frequencies, responsive to the measured induced current components, so that the coil generates a field substantially only at the respective driving frequency wherein the correction current components are cancellation currents determined so as to substantially cancel parasitic magnetic fields generated by the at least one other radiator coil.

8. A method according to claim 7, wherein adjusting the current comprises generating correction current components that are approximately equal in amplitude and opposite in phase to the induced current components measured at the respective one or more undesired frequencies.

9. A method in accordance with claim 7, wherein driving the radiator coil comprises storing data indicative of a waveform of the current with which the coil is to be driven, and wherein adjusting the current comprises modifying the data responsive to the induced current components.

10. A method in accordance with claim 7, and comprising iteratively repeating the steps of analyzing the current to measure the components at the undesired frequencies, and adjusting the current responsive to the measured induced current components, until the measured induced components are below a predetermined threshold.

11. A method for tracking an object, comprising:

driving a plurality of radiator coils with electrical currents at respective driving frequencies so as to generate a plurality of magnetic fields at the frequencies in a vicinity of an object being tracked;

analyzing the currents flowing in the coils so as to measure, in each of the coils, induced current components at one or more of the frequencies of the other coils;

adaptively adjusting the current driving each of the coils so as to include correction current components at the frequencies of the other coils, responsive to the measured induced current components, so that each of the coils generates a field substantially only at the respective driving frequency, wherein the correction current components are cancellation currents determined so as to substantially cancel parasitic magnetic fields generated by each of the coils in response to the magnetic fields generated by the other coils at the respective driving frequencies of the other coils;

placing one or more sensor coils at a locatable site on the object;

receiving signals generated by the sensor coils in response to the magnetic fields; and

analyzing the signals to determine position and orientation coordinates of the object.

12. An object tracking system, comprising:

a plurality of radiator coils; and

driver circuitry, coupled to drive the coils to generate magnetic fields at a plurality of driving frequencies, such that each of the coils is driven by a respective current that comprises a basic current at a respective one of the driving frequencies and cancellation currents at one or more of the other driving frequencies, so that each of the coils generates a field substantially only at the respective driving frequency, wherein cancellation currents are determined so as to substantially cancel pasitic magnetic fields generated by each of the coils in response to the magnetic fields generated by the dated by the other coils at the respective driving frequencies of the other coils;

one or more sensor coils, fixed to the object; and

processing circuity, coupled to receive and analyze currents induced in the sensor coils due to the magnetec fields, so as to determine coordinates of the object.