Blood constituent determination based on differential spectral analysis
First Claim
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1. A non-invasive in vivo method for obtaining a differential absorption spectrum relating to the concentration of analyte in living tissue comprising the steps of:
- a) illuminating the tissue with a first light beam which is varied in wavelength in a substantially continuous manner about a first wavelength over a first time period;
b) detecting the wavelength varied first light beam after the beam has traversed a first blood volume of tissue containing said analyte to produce a first absorption spectrum comprising a substantially continuous plot of absorption in said first volume versus wavelength;
c) changing the blood volume of tissue;
d) illuminating the changed blood volume of tissue with a second light beam which is varied in wavelength in a substantially continuous manner about a second wavelength over a second time period;
e) detecting the wavelength varied second light beam after the beam has traversed a second blood volume of tissue containing said analyte to produce a second absorption spectrum comprising a substantially continuous plot of absorption in said changed volume versus wavelength;
f) combining the two absorption spectrums to produce a differential absorption spectrum.
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Abstract
The present invention relates to the determination of an analyte or multiple analytes in blood using information derived from the differential optical absorption spectra of blood. Specifically, the information is derived from the differential spectra of tissue before and immediately after the volume of blood in the tissue has been changed.
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Citations
16 Claims
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1. A non-invasive in vivo method for obtaining a differential absorption spectrum relating to the concentration of analyte in living tissue comprising the steps of:
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a) illuminating the tissue with a first light beam which is varied in wavelength in a substantially continuous manner about a first wavelength over a first time period; b) detecting the wavelength varied first light beam after the beam has traversed a first blood volume of tissue containing said analyte to produce a first absorption spectrum comprising a substantially continuous plot of absorption in said first volume versus wavelength; c) changing the blood volume of tissue; d) illuminating the changed blood volume of tissue with a second light beam which is varied in wavelength in a substantially continuous manner about a second wavelength over a second time period; e) detecting the wavelength varied second light beam after the beam has traversed a second blood volume of tissue containing said analyte to produce a second absorption spectrum comprising a substantially continuous plot of absorption in said changed volume versus wavelength; f) combining the two absorption spectrums to produce a differential absorption spectrum. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A non-invasive method for obtaining a differential absorption spectrum relating to the concentration of analyte in living tissue comprising the steps of:
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a) illuminating the tissue at a first tissue site with a light beam which is varied in wavelength during a first time period; b) during a second time period changing the blood volume of the tissue at the first tissue site from a first volume to a second volume; c) detecting the light beam during the first time period after the wavelength varied beam has traversed the first volume of tissue containing said analyte to produce a first absorption spectrum; d) detecting the light beam during the second time period after the wavelength varied beam has traversed the second volume of tissue containing said analyte to produce a second absorption spectrum; e) combining the two absorption spectrum to produce a differential absorption spectrum which represents tissue absorption versus a spectrum of wavelengths. - View Dependent Claims (10, 11)
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12. Apparatus for non-invasive generation of a differential signal relating to the concentration of analyte in living tissue comprising:
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a) a light source generating a beam of light; b) a tuner varying the frequency of said beam of light over a predetermined time period; c) a photosensitive detector for detecting said frequency varying light after traversing said tissue; (ii) when the tissue contains a first volume of blood; and (iii) when the tissue contains a second volume of blood;
to produce two separate absorption signals a first one of which is proportional to the absorption of said frequency varying light by said tissue containing the first volume of blood versus frequency and a second of which is proportional to the absorption of said frequency varying light by said tissue containing the second volume of blood versus frequency; andd) generating means for generating said differential signal which is proportional to the difference between the light detected versus frequency for each signal detected in (c) (i) and (ii) above. - View Dependent Claims (13, 14, 15, 16)
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Specification