In-vivo electrochemical impedance spectroscopy (EIS)-based calibration
First Claim
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1. A method for real-time self-calibration of a glucose sensor, said glucose sensor including sensor electronics, a microcontroller, and at least one working electrode, the method comprising:
- inserting said glucose sensor into subcutaneous tissue of a user;
periodically measuring, by said sensor electronics, a value of the electrode current (Isig) for the working electrode, wherein said Isig is the sum of a Faradaic current component and a non-Faradaic current component;
performing, by said microcontroller, an electrochemical impedance spectroscopy (EIS) procedure for said at least one working electrode to obtain values of at least one impedance-based parameter for the at least one working electrode;
periodically repeating, by said microcontroller, said EIS procedure for said working electrode to obtain additional values of said at least one impedance-based parameter;
calculating, by said microcontroller, values of at least one EIS-based parameter based on said obtained values and additional values of the at least one impedance-based parameter;
monitoring the calculated values of said at least one EIS-based parameter for variations in said calculated values;
adjusting, by said microcontroller, a calibration factor for said glucose sensor, based on said variations in the calculated values and on only the Faradaic current component of the Isig, to obtain an adjusted calibration factor; and
using, by said microcontroller, said adjusted calibration factor to calculate a level of glucose in said user'"'"'s body,wherein the calibration factor is adjusted in accordance with the relation CF(t)=CFreference−
m(Rreference−
R(t)), wherein CF(t) is the calibration factor at time t, CFreference is a reference value for the calibration factor, Rreference is the value of membrane resistance when CF=CFreference, R(t) is membrane resistance at time t, and m is the gradient of a correlation between CF and R.
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Abstract
Electrochemical Impedance Spectroscopy (EIS) is used in conjunction with continuous glucose monitors and continuous glucose monitoring (CGM) to enable in-vivo sensor calibration, gross (sensor) failure analysis, and intelligent sensor diagnostics and fault detection. An equivalent circuit model is defined, and circuit elements are used to characterize sensor behavior.
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Citations
15 Claims
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1. A method for real-time self-calibration of a glucose sensor, said glucose sensor including sensor electronics, a microcontroller, and at least one working electrode, the method comprising:
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inserting said glucose sensor into subcutaneous tissue of a user; periodically measuring, by said sensor electronics, a value of the electrode current (Isig) for the working electrode, wherein said Isig is the sum of a Faradaic current component and a non-Faradaic current component; performing, by said microcontroller, an electrochemical impedance spectroscopy (EIS) procedure for said at least one working electrode to obtain values of at least one impedance-based parameter for the at least one working electrode; periodically repeating, by said microcontroller, said EIS procedure for said working electrode to obtain additional values of said at least one impedance-based parameter; calculating, by said microcontroller, values of at least one EIS-based parameter based on said obtained values and additional values of the at least one impedance-based parameter; monitoring the calculated values of said at least one EIS-based parameter for variations in said calculated values; adjusting, by said microcontroller, a calibration factor for said glucose sensor, based on said variations in the calculated values and on only the Faradaic current component of the Isig, to obtain an adjusted calibration factor; and using, by said microcontroller, said adjusted calibration factor to calculate a level of glucose in said user'"'"'s body, wherein the calibration factor is adjusted in accordance with the relation CF(t)=CFreference−
m(Rreference−
R(t)), wherein CF(t) is the calibration factor at time t, CFreference is a reference value for the calibration factor, Rreference is the value of membrane resistance when CF=CFreference, R(t) is membrane resistance at time t, and m is the gradient of a correlation between CF and R. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for real-time self-calibration of a glucose sensor, said glucose sensor including sensor electronics, a microcontroller, and at least one working electrode, the method comprising:
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inserting said glucose sensor into subcutaneous tissue of a user; periodically measuring, by said sensor electronics, a value of the electrode current (Isig) for the working electrode, wherein said Isig is the sum of a Faradaic current component and a non-Faradaic current component; performing, by said microcontroller, an electrochemical impedance spectroscopy (EIS) procedure for said at least one working electrode to obtain values of at least one impedance-based parameter for the at least one working electrode; periodically repeating, by said microcontroller, said EIS procedure for said working electrode to obtain additional values of said at least one impedance-based parameter; calculating, by said microcontroller, values of at least one EIS-based parameter based on said obtained values and additional values of the at least one impedance-based parameter; monitoring the calculated values of said at least one EIS-based parameter for variations in said calculated values; adjusting, by said microcontroller, a calibration factor for said glucose sensor, based on said variations in the calculated values and on only the Faradaic current component of the Isig, to obtain an adjusted calibration factor; and using, by said microcontroller, said adjusted calibration factor to calculate a level of glucose in said user'"'"'s body, wherein the calibration factor is adjusted in accordance with the relation CF(t)/CFreference=−
m(R(t)/Rreference), wherein CF(t) is the calibration factor at time t, CFreference is a reference value for the calibration factor, Rreference is the value of membrane resistance when CF=CFreference, R(t) is membrane resistance at time t, and m is the gradient of a correlation between CF and R.
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Specification