DYNAMIC ADAPTIVE RESPIRATION COMPENSATION WITH AUTOMATIC GAIN CONTROL

• US 20120172702A1
• Filed: 12/29/2010
• Published: 07/05/2012
• Est. Priority Date: 12/29/2010
• Status: Active Grant

• Current Assignee: St. Jude Medical (Abbott Laboratories Incorporated)
• Original Assignee: St. Jude Medical (Abbott Laboratories Incorporated)
• Inventors: Koyrakh, Lev A., VOTH, ERIC J., HAUCK, JOHN A., SCHWEITZER, JEFFREY A.
• Granted Patent: US 9,113,807 B2
• Time in Patent Office: Days
• US Class Current: 600/408
• CPC Class Codes: A61B 5/0044 for the heart
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0536 Impedance imaging, e.g. by tomography
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• 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 5/061 Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body A61B1/00158 takes precedence
• CPC Class Codes: A61B 5/063 using impedance measurements
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7267 involving training the classification device
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: H04L 25/0278 Arrangements for impedance matching

Abstract

A system for determining a location of an electrode of a medical device (e.g., a catheter) in a body of a patient includes a localization block for producing an uncompensated electrode location, a motion compensation block for producing a compensation signal (i.e., for respiration, cardiac, etc.), and a mechanism for subtracting the compensation signal from the uncompensated electrode location. The result is a corrected electrode location substantially free of respiration and cardiac artifacts. The motion compensation block includes a dynamic adaptation feature which accounts for changes in a patient'"'"'s respiration patterns as well as intentional movements of the medical device to different locations within the patient'"'"'s body. The system further includes an automatic compensation gain control which suppresses compensation when certain conditions, such as noise or sudden patch impedance changes, are detected.

Claims

1. A method for determining a compensated location of an electrode of a medical device within a body of a patient, comprising the steps of:

(A) mean-adjusting patch electrode impedance data associated with body surface electrodes and electrode location data associated with said electrode;

(B) determining an acquired set of weights such that a linear combination of the product of the weights and mean-adjusted patch impedance data correspond to the mean-adjusted electrode location data;

(C) repeating steps (A) and (B) for a plurality of different time periods and producing a plurality of sets of weights, and updating a reference set of weights, based on a learning parameter, as each successive acquired sets of weights is determined in step (B);

(D) determining a compensation signal using the reference set of weights and patch electrode impedance data; and

(E) computing a compensated electrode location using an uncompensated electrode location and the compensation signal.

2. The method of claim 1 wherein said location includes one of a position and orientation (P&

O) in a reference coordinate system, said method further including the step of selecting one or more axes for compensation, said step of determining a set of weights being further performed for each selected axis.

3. The method of claim 1 wherein said step of determining a set of weights involves principal component analysis (PCA).

4. The method of claim 1 wherein said mean-adjusted patch data and electrode location data are in matrix form, said step of determining a set of weights includes the sub-steps of:

performing singular value decomposition of the mean-adjusted patch data matrix;

obtaining the pseudo-inverse of the mean-adjusted patch data matrix and applying regularization;

determining said set of weights in accordance with the product of the pseudo-inverse mean-adjusted patch data matrix and the electrode location data matrix.

5. The method of claim 3 wherein updating a reference set of weights includes the sub step of summing the current reference set of weights with the product of the learning parameter and a difference between a most-recent acquired set of weights and the current reference set of weights.

6. The method of claim 5 wherein the learning parameter is preselected between zero and one, inclusive.

7. The method of claim 5 further including the steps of:

varying the learning parameter in accordance with a distance between successive, acquired sets of weights.

8. The method of claim 7 wherein said step of varying the learning parameter includes the sub-step of:

exponentially reducing the learning parameter when the distance between successive, acquired sets of weights exceeds a threshold thereby suppressing learning parameter adaptation.

9. The method of claim 1 wherein said step of determining a compensation signal involves automatically controlling a gain parameter.

10. The method of claim 9 further including the step of setting the gain parameter to a default value of about 1.

11. The method of claim 10 further including the steps of:

determining a moving average of the compensation signal;

determining an average deviation of the compensation signal from the moving average;

determining a current deviation between a current value of the compensation signal and the moving average;

reducing the default value of the gain parameter in accordance with the ratio between the average deviation and the current deviation when the current deviation exceeds a deviation threshold.

12. The method of claim 11 wherein said location includes one of a position and orientation (P&

O) in a reference coordinate system, said method further including the step of selecting one or more axes in the coordinate system for compensation, said gain parameter having respective values for each one of said selected axes.

13. The method of claim 1 wherein the electrode is a first electrode and the compensated electrode location is a compensated first electrode location having associated therewith a coordinate within a reference coordinate system, the method further including the steps of:

associating the coordinate with the compensation signal;

determining an uncompensated second electrode location associated with a second electrode;

applying the compensation signal to the uncompensated second electrode location to produce a compensated second electrode location when the second electrode location matches the coordinate within a predetermined range.

14. A system for determining a motion compensated location of an electrode of a medical device within a body of a patient, comprising:

a main control unit including (i) a localization block configured to produce an uncompensated electrode location signal;

(ii) a compensation block configured to generate a compensation signal; and

(iii) a mechanism to subtract said compensation signal from said uncompensated location signal to output a compensated location signal;

said compensation block being configured to (i) mean-adjust patch electrode impedance data associated with body surface electrodes and electrode location data associated with said electrode;

(ii) acquire a set of weights such that a linear combination of the product of said set of weights and said mean-adjusted patch impedance data correspond to said mean-adjusted electrode location data;

(iii) to further mean-adjust patch impedance and electrode location data for further time periods to produce a plurality of acquired sets of weights;

(iv) to update a reference set of weights, based on a learning parameter, for each successive acquired sets of weights; and

(v) to determine said compensation signal based on said reference set of weights and patch electrode impedance data.

15. The system of claim 14 wherein said mean-adjusted patch and electrode data are in matrix form, said compensation block being further configured (i) to perform singular value decomposition of the mean-adjusted patch data;

(ii) to obtain the pseudo-inverse of said mean-adjusted patch data matrix and to apply regularization; and

(iii) to determine said set of weights in accordance with the product of said pseudo-inverse mean-adjusted patch data matrix and said electrode location data matrix.

16. The system of claim 14 wherein compensation block is further configured to sum said reference set of weights with the product of a learning parameter and a difference between a most-recently acquired set of weights and said reference set of weights.

17. The system of claim 16 wherein said compensation block is further configured to vary said learning parameter in accordance with a distance between successive, acquired sets of weights.

18. The system of claim 14 wherein said compensation block is further configured to compute said compensation signal as a function of a gain parameter.

19. The system of claim 18 wherein said compensation block is further configured to determine (i) a moving average of said compensation signal;

(ii) an average deviation of said compensation signal from said moving average; and

(iii) a value of said gain parameter as a function of a ratio of said average deviation and a current deviation between the current compensation signal and said moving average.

20. The system of claim 14 wherein said electrode is a first electrode and said compensated electrode location is a compensated first electrode location having associated therewith a coordinate within a reference coordinate system, said localization block being configured to determine an uncompensated second electrode location associated with a second electrode, said compensation block being further configured to (i) associate said coordinate with said compensation signal;

and (ii) apply said compensation signal to said uncompensated second electrode location to produce a compensated second electrode location when said second electrode location matches said coordinate within a predetermined range.

21. A method for determining a compensated location of magnetic field sensor of a medical device within a body of a patient, comprising the steps of:

(A) mean-adjusting patch electrode impedance data associated with body surface electrodes and magnetic sensor location data associated with said magnetic field sensor;

(B) determining an acquired set of weights such that a linear combination of the product of the weights and mean-adjusted patch impedance data correspond to the mean-adjusted magnetic sensor location data;

(C) repeating steps (A) and (B) for a plurality of different time periods and producing a plurality of sets of weights, and updating a reference set of weights, based on a learning parameter, as each successive acquired sets of weights is determined in step (B);

(D) determining a compensation signal using the reference set of weights and patch electrode impedance data; and

(E) computing a compensated magnetic sensor location using an uncompensated magnetic sensor location and the compensation signal.