Apparatus and methods for non-invasive measurement of a substance within a body
First Claim
1. A method for measuring a concentration of a substance in a bloodstream of a body, the method comprising the steps of:
- measuring a first amount of infrared (IR) radiation absorbed or emitted from the body in a first IR wavelength band in which the substance exhibits IR absorption or emission, and generating a first signal having a first radiation measurement value indicative of the first amount;
measuring a second amount of IR radiation absorbed or emitted from the body in a second IR wavelength band different from the first IR wavelength band and including wavelengths in which the substance exhibits no more than negligible IR absorption or emission, and generating a second signal having a second radiation measurement value indicative of the second amount;
measuring a temperature of a surface on the body and generating a third signal having a third value indicative of the temperature of the surface;
measuring an ambient temperature and generating a fourth signal having a fourth value indicative of the ambient temperature;
providing a memory device in which is stored an empirically-derived look-up table containing data correlating values for the concentration of the substance in the bloodstream with (a) ambient temperature values, (b) body surface temperature values, and (c) normalized radiation parameter ratio values, each of which is determined by the ratio of (1) a radiation parameter value in the first IR wavelength band normalized against a first blackbody radiation parameter value in the first IR wavelength band to (2) a radiation parameter value in the second IR wavelength band normalized against a second predetermined blackbody radiation parameter value in the second IR wavelength band;
providing a processor configured to receive the first, second, third, and fourth signals, the processor being operably associated with the memory device so as to access the lookup table therefrom; and
operating the processor to (a) normalize the first radiation measurement value against the first predetermined blackbody radiation value, (b) normalize the second radiation measurement value against the second predetermined blackbody radiation value, (c) calculate a normalized radiation parameter ratio value as the ratio of the normalized first radiation measurement value to the normalized second radiation measurement value, (d) correct the normalized radiation parameter ratio value using the third and fourth values to obtain a corrected normalized radiation parameter ratio value, and (e) determine from the lookup table the concentration of the substance in the bloodstream correlated with the corrected normalized radiation parameter ratio value.
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Abstract
Embodiments of the present system and methods measure a concentration of a substance, such as glucose, in a body. The present embodiments measure a first amount of infrared (IR) radiation absorbed or emitted from the body in a first wavelength band, and a second amount of IR radiation absorbed or emitted from the body in a second wavelength band. The present embodiments also measure a temperature at a surface of the body and an ambient temperature. A normalized ratio parameter is calculated from the four measurements, and the concentration of the substance in the body is calculated by correlating the normalized ratio parameter with the body surface temperature and the ambient temperature using an empirically derived lookup table. Also disclosed are methods for creating the empirically derived lookup table.
30 Citations
17 Claims
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1. A method for measuring a concentration of a substance in a bloodstream of a body, the method comprising the steps of:
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measuring a first amount of infrared (IR) radiation absorbed or emitted from the body in a first IR wavelength band in which the substance exhibits IR absorption or emission, and generating a first signal having a first radiation measurement value indicative of the first amount; measuring a second amount of IR radiation absorbed or emitted from the body in a second IR wavelength band different from the first IR wavelength band and including wavelengths in which the substance exhibits no more than negligible IR absorption or emission, and generating a second signal having a second radiation measurement value indicative of the second amount; measuring a temperature of a surface on the body and generating a third signal having a third value indicative of the temperature of the surface; measuring an ambient temperature and generating a fourth signal having a fourth value indicative of the ambient temperature; providing a memory device in which is stored an empirically-derived look-up table containing data correlating values for the concentration of the substance in the bloodstream with (a) ambient temperature values, (b) body surface temperature values, and (c) normalized radiation parameter ratio values, each of which is determined by the ratio of (1) a radiation parameter value in the first IR wavelength band normalized against a first blackbody radiation parameter value in the first IR wavelength band to (2) a radiation parameter value in the second IR wavelength band normalized against a second predetermined blackbody radiation parameter value in the second IR wavelength band; providing a processor configured to receive the first, second, third, and fourth signals, the processor being operably associated with the memory device so as to access the lookup table therefrom; and operating the processor to (a) normalize the first radiation measurement value against the first predetermined blackbody radiation value, (b) normalize the second radiation measurement value against the second predetermined blackbody radiation value, (c) calculate a normalized radiation parameter ratio value as the ratio of the normalized first radiation measurement value to the normalized second radiation measurement value, (d) correct the normalized radiation parameter ratio value using the third and fourth values to obtain a corrected normalized radiation parameter ratio value, and (e) determine from the lookup table the concentration of the substance in the bloodstream correlated with the corrected normalized radiation parameter ratio value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus for measuring a concentration of a substance in a bloodstream of a body, comprising:
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an infrared (IR) radiation detection device operable to detect the IR radiation absorbed or emitted from the body, and to generate a first output signal having a first radiation measurement value indicative of a first amount of IR radiation absorbed or emitted from the body in a first IR wavelength band in which the substance exhibits IR absorption or emission, and a second output signal having a second radiation measurement value indicative of a second amount of IR radiation absorbed or emitted from the body in a second IR wavelength band different from the first IR wavelength band and including wavelengths in which the substance exhibits no more than negligible IR absorption or emission; a first temperature sensor configured to measure a surface temperature at a surface of the body and to generate a third output signal having a third value indicative of the surface temperature; a second temperature sensor configured to measure an ambient temperature and to generate a fourth output signal having a fourth value indicative of the ambient temperature; a memory device in which is stored an empirically-derived look-up table containing data correlating values for the concentration of the substance in the bloodstream with (a) ambient temperature values, (b) body surface temperature values, and (c) normalized radiation parameter ratio values, each of which is determined by the ratio of (1) a radiation parameter value in the first IR wavelength band normalized against a first blackbody radiation parameter value in the first IR wavelength band to (2) a radiation parameter value in the second IR wavelength band normalized against a second predetermined blackbody radiation parameter value in the second IR wavelength band; and a processor configured to receive the first, second, third, and fourth signals, the processor being operatively associated with the memory device so as to access the lookup table therefrom; wherein the processor is operable to (a) normalize the first radiation measurement value against the first predetermined blackbody radiation value, (b) normalize the second radiation measurement value against the second predetermined blackbody radiation value, (c) calculate a normalized radiation parameter ratio value as the ratio of the normalized first radiation measurement value to the normalized second radiation measurement value, (d) correct the normalized radiation parameter ratio value using the third and fourth values to obtain a corrected normalized radiation parameter ratio value, and (e) determine from the lookup table the concentration of the substance in the bloodstream correlated with the corrected normalized radiation parameter ratio value. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification