Apparatus and method for determining the relative position and orientation of neurostimulation leads

• US 20060122653A1
• Filed: 01/30/2006
• Published: 06/08/2006
• Est. Priority Date: 12/04/2001
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Inventors: Thacker, James R., Bradley, Kerry
• Granted Patent: US 7,684,869 B2
• Time in Patent Office: Days
• US Class Current: 607/28
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61N 1/0551 Spinal or peripheral nerve electrodes

Abstract

Interelectrode impedance or electric field potential measurements are used to determine the relative orientation of one lead to other leads in the spinal column or other body/tissue location. Interelectrode impedance is determined by measuring impedance vectors. The value of the impedance vector is due primarily to the electrode-electrolyte interface, and the bulk impedance between the electrodes. The bulk impedance between the electrodes is, in turn, made up of (1) the impedance of the tissue adjacent to the electrodes, and (2) the impedance of the tissue between the electrodes. In one embodiment, the present invention makes both monopolar and bipolar impedance measurements, and then corrects the bipolar impedance measurements using the monopolar measurements to eliminate the effect of the impedance of the tissue adjacent the electrodes. The orientation and position of the leads may be inferred from the relative minima of the corrected bipolar impedance values. These corrected impedance values may also be mapped and stored to facilitate a comparison with subsequent corrected impedance measurement values. Such comparison allows a determination to be made as to whether the lead position and/or orientation has changed appreciably over time. In another embodiment, one or more electrodes are stimulated and the resulting electric field potential on the non-stimulated electrodes is measured. Such field potential measurements provide an indication of the relative orientation of the electrodes. Once known, the relative orientation may be used to track lead migration, to setup stimulation configurations and parameters for nominal stimulation and/or navigation. Also, such measurements allow automatic adjustment of stimulation energy to a previously-defined optimal potential field in the case of lead migration or postural changes.

Claims

1. A method for determining the relative lead position of multiple-electrode leads, comprising:

measuring impedance vectors between lead electrodes; and

inferring the relative position of the leads by the relative minima of the impedance vectors.

2. A method as claimed in claim 1, wherein measuring impedance vectors between lead electrodes comprises:

measuring monopolar impedances for all lead electrodes;

measuring bipolar impedances between each lead electrode on opposing leads; and

correcting the bipolar impedances for adjacent tissue impedance.

3. A method as claimed in claim 2, further comprising:

mapping the corrected bipolar impedances to create an impedance map that reveals the relative orientation of the leads.

4. A method as claimed in claim 3, further comprising:

referring to the map at a future time to determine whether the relative lead position has changed, and if the relative lead position has changed, the magnitude of the change.

5. A method, comprising:

determining the position of a first lead having a plurality electrodes relative to a second lead having a plurality of electrodes by measuring impedance vectors between respective electrode pairs that each include one of the electrodes on the first lead and one of the electrodes on the second lead.

6. A method as claimed in claim 5, further comprising:

comparing the determined position of the first lead relative to the second lead to a previously determined position of the first lead relative to the second lead.

7. A method as claimed in claim 6, further comprising:

reprogramming in response to the comparison of the determined position of the first lead relative to the second lead to a previously determined position of the first lead relative to the second lead.

8. A method as claimed in claim 5, further comprising:

setting up a navigation table based on the determined position of the first lead relative to the second lead.

9. A method as claimed in claim 5, wherein measuring impedance vectors comprises:

measuring monopolar impedances for all electrodes;

measuring bipolar impedances between each electrode pair; and

correcting the bipolar impedances for adjacent tissue impedance.

10. An apparatus for use with first and second leads that include respective pluralities of electrodes, the apparatus comprising:

means for delivering stimulation energy to the electrodes on the first and second leads; and

means for measuring a corrected bipolar impedance between respective electrode pairs that each include one of the electrodes on the first lead and one of the electrodes on the second lead.

11. An apparatus as claimed in claim 10, wherein the means for measuring comprises means for measuring a corrected bipolar impedance between each possible pair of electrodes that includes one of the electrodes on the first lead and one of the electrodes on the second lead.

12. An apparatus for use with first and second leads that include respective pluralities of electrodes, the apparatus comprising:

circuitry to deliver stimulation energy to the electrodes on the first and second leads; and

circuitry to measure a corrected bipolar impedance between respective electrode pairs that each include one of the electrodes on the first lead and one of the electrodes on the second lead.

13. An apparatus as claimed in claim 12, wherein the circuitry to measure a corrected bipolar impedance comprises circuitry to measure a corrected bipolar impedance between each possible pair of electrodes that includes one of the electrodes on the first lead and one of the electrodes on the second lead.

14. An apparatus as claimed in claim 12, wherein

the circuitry to deliver stimulation energy and the circuitry to measure a corrected bipolar impedance are carried within an implantable pulse generator;

the implantable pulse generator includes a case electrode; and

the circuitry to measure a corrected bipolar impedance comprises

circuitry to measure the impedances between each lead electrode and the case electrode,

circuitry to measure the bipolar impedances between each electrode pair, and

circuitry to correct the bipolar impedances for adjacent tissue impedance.

15. An apparatus for use with first and second leads that include respective pluralities of electrodes, the apparatus comprising:

means for applying a stimulus to a selected group of the electrodes;

means for measuring the voltage at the electrodes not included in the group of electrodes to which the stimulus is applied; and

means for determining the relative position or orientation of the leads based on the measured voltage at the electrodes not included in the group of electrodes to which the stimulus is applied.

16. An apparatus as claimed in claim 15, further comprising:

means for determining whether changes in the measured voltage at the electrodes have occurred over time; and

means for analyzing whether the changes that have occurred in the voltage at the electrodes over time are indicative of a change in the relative position or orientation of the electrodes.

17. An apparatus as claimed in claim 15, further comprising:

means for automatically initiating corrective action in response to a change in the relative position or orientation of the leads.

18. An apparatus as claimed in claim 17, wherein the corrective action includes changing the electrodes through which stimulus is applied.

19. An apparatus as claimed in claim 17, wherein the corrective action includes adjusting the stimulus to a previously-defined optimal voltage.

20. An apparatus for use with first and second leads that include respective pluralities of electrodes, the apparatus comprising:

circuitry to apply a stimulus to a selected group of the electrodes;

circuitry to measure the voltage at the electrodes not included in the group of electrodes to which the stimulus is applied; and

circuitry to determine the relative position or orientation of the leads based on the measured voltage at the electrodes not included in the group of electrodes to which the stimulus is applied.

21. An apparatus as claimed in claim 20, further comprising:

circuitry to determine whether changes in the measured voltage at the electrodes have occurred over time; and

circuitry to analyze whether the changes that have occurred in the voltage at the electrodes over time are indicative of a change in the relative position or orientation of the electrodes.

22. An apparatus as claimed in claim 20, further comprising:

circuitry to automatically initiate corrective action in response to a change in the relative position or orientation of the leads.

23. An apparatus as claimed in claim 22, wherein the corrective action includes changing the electrodes through which stimulus is applied.

24. An apparatus as claimed in claim 22, wherein the corrective action includes adjusting the stimulus to a previously-defined optimal voltage.