Methods, systems, and devices for sensor fusion

• US 10,349,872 B2
• Filed: 12/28/2015
• Issued: 07/16/2019
• Est. Priority Date: 12/28/2015
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Varsavsky, Andrea, Lu, Yunfeng, Mung, Jay
• Primary Examiner(s): Weston, Tiffany
• Assistant Examiner(s): Tran, Tho Q
• Application Number:
  US14/980,260
• Publication Number:
  US 20170181677A1
• Time in Patent Office: 1,296 Days
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

A single, optimal, fused sensor glucose value may be calculated based on respective sensor glucose values of a plurality of redundant working electrodes (WEs) of a glucose sensor. Respective electrochemical impedance spectroscopy (EIS) procedures may be performed for each of the WEs to obtain values of membrane resistance (Rmem) for each WE. A noise value and a calibration factor (CF) value may be calculated for each WE, and respective fusion weights may be calculated for Rmem, noise, and CF for each WE. An overall fusion weight may then be calculated based on the WE'"'"'s Rmem fusion weight, noise fusion weight, and CF fusion weight, such that a single, optimal, fused sensor glucose value may be calculated based on the respective overall fusion weight and sensor glucose value of each of the plurality of redundant working electrodes.

Claims

1. A method of calculating a single, fused sensor glucose value based on respective sensor glucose values of a plurality of redundant working electrodes of a glucose sensor, said glucose sensor including a microcontroller, the method comprising:

performing, by said microcontroller, respective electrochemical impedance spectroscopy (EIS) procedures for each of the plurality of redundant working electrodes to obtain values of membrane resistance (Rmem) for each said working electrode;

calculating, by said microcontroller, a respective Rmem fusion weight for each said working electrode based on the respective Rmem value for each of the plurality of redundant working electrodes;

obtaining, by said microcontroller, a noise value for each of the plurality of redundant working electrodes;

calculating, by said microcontroller, a respective noise fusion weight for each said working electrode based on the respective noise value for each of the plurality of redundant working electrodes;

obtaining, by said microcontroller, a calibration factor (CF) value for each of the plurality of redundant working electrodes;

calculating, by said microcontroller, a respective CF fusion weight for each said working electrode based on the respective CF value for each of the plurality of redundant working electrodes;

for each of the plurality of redundant working electrodes, combining, by said microcontroller, the respective noise fusion weight and CF fusion weight to calculate a combined noise and CF fusion weight, wherein said combined noise and CF fusion weight is calculated by weighting and averaging the respective noise fusion weight and CF fusion weight by a predefined parameter;

for each of the plurality of redundant working electrodes, calculating, by said microcontroller, an overall fusion weight based on said electrode'"'"'s Rmem fusion weight and combined noise and CF fusion weight;

calculating, by said microcontroller, said single, fused sensor glucose value based on the respective overall fusion weight and sensor glucose value of each of the plurality of redundant working electrodes;

determining, by said microcontroller, whether said single, fused sensor glucose value falls within a calculated range; and

generating a signal, by said microcontroller, to display said single, fused sensor glucose value to a user of said glucose sensor when said single, fused sensor glucose value falls within said range.

2. The method of claim 1, further including performing a validity check on said respective sensor glucose values.

3. The method of claim 2, wherein the single fused sensor glucose value is determined to be invalid if all of the sensor glucose values are invalid.

4. The method of claim 2, wherein the glucose sensor includes two redundant working electrodes, and wherein, if the sensor glucose value for one of said two redundant working electrodes is valid and the sensor glucose value for the other of the two redundant working electrodes is invalid, then the fused sensor glucose value is equal to the valid sensor glucose value.

5. The method of claim 1, wherein said Rmem values are obtained based on respective values of 1 kHz real impedance.

6. The method of claim 1, wherein, after a predefined period of time from sensor start, the value of said respective Rmem fusion weight for each of the plurality of redundant working electrodes is equal to 0.

7. The method of claim 6, wherein said predefined period of time is about 25 hours.

8. The method of claim 6, wherein, between sensor start and expiry of said calculated period of time, the value of each said respective Rmem fusion weight is modified by a first variable to generate a modified Rmem fusion weight, said variable being a function of the variance in respective Rmem fusion weight values for the plurality of redundant working electrodes.

9. The method of claim 8, further including modifying said combined noise and CF fusion weight by a second variable to calculate a modified combined noise and CF fusion weight.

10. The method of claim 9, wherein said overall fusion weight is calculated based on said modified Rmem fusion weight and said modified combined noise and CF fusion weight.

11. The method of claim 9, wherein the sum of the values of said first and second variables equals 1.

12. The method of claim 1, wherein each said respective EIS procedure is performed for a range of frequencies.

13. A program code storage device comprising:

a non-transitory computer-readable medium; and

computer-readable program code, stored on the computer-readable medium, the computer-readable program code having instructions which, when executed, cause a physical microcontroller to perform a method of calculating and displaying a single, fused sensor glucose value based on respective sensor glucose values of a plurality of redundant working electrodes of a glucose sensor by;

performing respective electrochemical impedance spectroscopy (EIS) procedures for each of the plurality of redundant working electrodes to obtain values of membrane resistance (Rmem) for each said working electrode;

calculating a respective Rmem fusion weight for each said working electrode based on the respective Rmem value for each of the plurality of working electrodes;

obtaining a noise value for each of the plurality of working electrodes;

calculating a respective noise fusion weight for each said working electrode based on the respective noise value for each of the plurality of working electrodes;

obtaining a calibration factor (CF) value for each of the plurality of working electrodes;

calculating a respective CF fusion weight for each said working electrode based on the respective CF value for each of the plurality of working electrodes;

combining the respective noise fusion weight and CF fusion weight to calculate a combined noise and CF fusion weight by weighting and averaging the respective noise fusion weight and CF fusion weight by a predefined parameter;

for each of the plurality of electrodes, calculating an overall fusion weight based on said electrode'"'"'s Rmem fusion weight and combined noise and CF fusion weight;

calculating said single, fused sensor glucose value based on the respective overall fusion weight and sensor glucose value of each of the plurality of redundant working electrodes;

determining whether said single, fused sensor glucose value falls within a calculated range; and

displaying said single, fused sensor glucose value to a user of said glucose sensor when said fused sensor glucose value falls within said range.

14. The device of claim 13, wherein the computer-readable program code has instructions which, when executed, further cause the microcontroller to perform a validity check on said respective sensor glucose values.

15. The device of claim 13, wherein the computer-readable program code has instructions which, when executed, further cause the microcontroller to, for each working electrode, modify the value of Rmem fusion weight by a first variable to generate a modified Rmem fusion weight, said variable being a function of the variance in respective Rmem fusion weight values for the plurality of working electrodes.

16. The device of claim 15, wherein the computer-readable program code has instructions which, when executed, further cause the microcontroller to modify said combined noise and CF fusion weight by a second variable to calculate a modified combined noise and CF fusion weight.

17. The device of claim 16, wherein the computer-readable program code has instructions which, when executed, further cause the microcontroller to calculate said overall fusion weight based on said modified Rmem fusion weight and said modified combined noise and CF fusion weight.