Method for non-invasive blood analyte measurement with improved optical interface
First Claim
1. A method for non-invasive spectroscopic analysis of blood analytes in a tissue through a surface thereof, said method comprising the steps of:
- (a) providing a means for irradiating said tissue with infrared energy;
(b) providing an output element, said output element operatively connected to a spectrum analyzer;
(c) providing a hydrophilic index-matching compound, said index-matching compound conforming to said surface of said tissue when applied thereto and having a refractive index closely matched to that of said tissue surface;
(d) disposing a quantity of said compound between said output element and said tissue surface to couple said output clement to said tissue surface and said analytes in said tissue through said index-matching compound;
(e) irradiating said tissue with said infrared energy so that there is differential absorption of said infrared energy in said tissue; and
,(f) collecting infrared energy exiting said tissue through said output element as coupled to said tissue surface through said index-matching compound and quantifying said infrared energy with said spectrum analyzer.
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Abstract
A method for non-invasively measuring the concentration of an analyte, particularly blood analyte in blood. The method utilizes spectrographic techniques in conjunction with an improved optical interface between a sensor probe and a skin surface or tissue surface of the body containing the blood to be analyzed. An index-matching medium is disclosed to improve the interface between the sensor probe and skin surface during spectrographic analysis. In a preferred embodiment, the blood analyte concentration in blood is quantified utilizing a partial squares analysis relative to a model incorporating analysis of plural known blood samples.
213 Citations
30 Claims
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1. A method for non-invasive spectroscopic analysis of blood analytes in a tissue through a surface thereof, said method comprising the steps of:
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(a) providing a means for irradiating said tissue with infrared energy; (b) providing an output element, said output element operatively connected to a spectrum analyzer; (c) providing a hydrophilic index-matching compound, said index-matching compound conforming to said surface of said tissue when applied thereto and having a refractive index closely matched to that of said tissue surface; (d) disposing a quantity of said compound between said output element and said tissue surface to couple said output clement to said tissue surface and said analytes in said tissue through said index-matching compound; (e) irradiating said tissue with said infrared energy so that there is differential absorption of said infrared energy in said tissue; and
,(f) collecting infrared energy exiting said tissue through said output element as coupled to said tissue surface through said index-matching compound and quantifying said infrared energy with said spectrum analyzer. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for eliminating critical angle loss of diffusely reflected infrared energy at a tissue surface, said loss occurring from total internal reflection of said infrared energy when exiting from said tissue surface in a non-invasive spectroscopic method of measuring blood analytes in a tissue beneath said tissue surface, said method comprising the steps of:
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(a) providing a means for irradiating said tissue with infrared energy of multiple wavelengths; (b) providing an output element, said output element operatively connected to a spectrum analyzer; (c) providing a hydrophilic index-matching compound, said index matching compound having a refractive index closely matched to that of said tissue surface, and disposing a quantity of said compound between said output element and said tissue surface to couple said output element to said tissue surface and said analytes in said tissue through said index-matching compound; (d) irradiating said tissue with said multiple wavelengths of infrared energy so that there is differential absorption of at least some of said wavelengths in said tissue; and
,(e) collecting diffusely reflected infrared energy exiting said tissue through said output element as coupled to said tissue surface through said index-matching compound and quantifying said diffusely reflected infrared energy with said spectrum analyze. - View Dependent Claims (9, 10, 11, 12)
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13. A non-invasive method for measuring the concentration of a blood analyte in human tissue by measuring diffusely reflected infrared energy from said human tissue comprising the steps of:
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(a) providing an apparatus for measuring diffusely reflected infrared energy, said apparatus including an energy source emitting infrared energy at multiple wavelengths operatively connected to an input element, said apparatus further including an output element operatively connected to a spectrum analyzer; (b) providing a hydrophilic index-matching compound and disposing a quantity of said compound between said human tissue and said input element and output element to couple said elements with said analyte-containing tissue through said index-matching compound; (c) irradiating said tissue through said input element with multiple wavelengths of infrared energy so that there is differential absorption of at least some of said wavelengths; and
,(d) collecting at least a portion of the non-absorbed infrared energy with said output element, wherein said output element coupled through said index-matching compound prevents loss of diffusely reflected infrared energy by total reflection exiting said tissue, followed by measuring the intensities of said wavelengths of the non-absorbed infrared energy with subsequent calculation of blood analyte concentration. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. A fluid composition for providing an optical interface between a skin surface on a body and a spectrographic sensor element when measuring the absorption of infrared energy by constituents under said skin surface within said body at multiple wavelengths, said fluid composition comprising:
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(a) about 80% to about 99% of a mixture of perfluorocarbons and chlorofluorocarbons; and
,(b) about 1% to about 20% of a hydrophilic additive. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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28. A quantitative analysis instrument for non-invasive measurement of a blood analyte in human tissue, said instrument comprising:
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(a) a source of at least three wavelengths of infrared energy, said wavelengths being in the range of 500 to 2500 nm; (b) an input sensor clement for directing said infrared energy into said tissue and an output sensor element for collecting at least a portion of the non-absorbed diffusely reflected infrared energy from said tissue; (c) said input and output sensors being adapted to permit positioning of a hydrophilic index-matching compound across their surface and between said input and output sensors and the analyte-containing tissue; (d) at least one detector for measuring a set of intensities of at least a portion of the non-absorbed diffusely reflected infrared energy from said tissue collected by said output sensor element; (e) electronics for processing said measured set of intensities to estimate the value of said blood analyte; and (f) means for indicating said estimated value of said blood analyte. - View Dependent Claims (29, 30)
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Specification