Non-invasive blood analysis by near infrared absorption measurements using two closely spaced wavelengths
First Claim
1. A blood-analyte detection apparatus comprising:
- infrared illumination means for non-invasively illuminating an in vivo blood sample in a patient at least two wavelengths in the near infrared spectrum;
detector means for non-invasively measuring light absorbed by said sample at least a first data wavelength and a second reference wavelength, and for converting said detected light into electrical signals, said signals being indicative of the intensity of said detected light at each wavelength;
the detector means further characterized as measuring light absorption at two closely-spaced wavelengths said first and second wavelengths spaced by less than about 60 nanometers in order to minimize inference from extraneous factors.
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Accused Products
Abstract
Systems and methods for non-invasive blood analysis are disclosed in which blood is illuminated at a plurality of discrete wavelengths selected from the near infrared spectrum. Measurements of the intensity of transmitted or reflected light at such wavelengths are taken, and an analysis of transmittance or reflectance ratios for various wavelengths is performed. Changes in the ratios can be correlated with specific near infrared (IR) absorption peak for the analyte which varies with concentration of the analyte (the data wavelength) and the a second (reference) wavelength being sufficiently removed from the first so that measurements of light absorption at this second wavelength are relatively insensitive to the concentration of the analyte and yet the second wavelength is sufficiently close to the first wavelength to minimize interference from scattering effects and the like. Typically, the window bracketing these closely spaced wavelengths will be less than about 300 nm and preferably less than about 60 nm wide and, in some instances, more preferably less than about 30 nm wide.
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Citations
20 Claims
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1. A blood-analyte detection apparatus comprising:
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infrared illumination means for non-invasively illuminating an in vivo blood sample in a patient at least two wavelengths in the near infrared spectrum; detector means for non-invasively measuring light absorbed by said sample at least a first data wavelength and a second reference wavelength, and for converting said detected light into electrical signals, said signals being indicative of the intensity of said detected light at each wavelength; the detector means further characterized as measuring light absorption at two closely-spaced wavelengths said first and second wavelengths spaced by less than about 60 nanometers in order to minimize inference from extraneous factors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for detecting an analyte in a blood sample, comprising the steps of:
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illuminating a source of blood non-invasively through the tissue of a subject at a plurality of wavelengths within a narrow window selected in the near infrared spectrum; detecting light effected by said blood and converting said detected light into electrical signals indicative of the intensity of said effected light at a plurality of wavelengths selected from the near infrared spectrum, including a first data wavelength and a second reference wavelength separated by less than about 60 nanometers; analyzing said electrical signals to derive a ratio for at least two of said wavelengths; and comparing said ratio to a predetermined value to detect the presence of an analyte in said blood. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification