Compact apparatus for noninvasive measurement of glucose through near-infrared spectroscopy

Abstract

The invention involves the monitoring of a biological parameter through a compact analyzer. The preferred apparatus is a spectrometer based system that is attached continuously or semi-continuously to a human subject and collects spectral measurements that are used to determine a biological parameter in the sampled tissue. The preferred target analyte is glucose. The preferred analyzer is a near-IR based glucose analyzer for determining the glucose concentration in the body.

1 . An apparatus for noninvasive measurement of glucose through near-infrared spectroscopy, comprising: 
 a base module comprising a grating and a detector array;    a sample module interfaced to a sample site, said sample module coupled to said base module, said sample module comprising an illumination source;    a communication bundle for carrying optical and/or electrical signals between said base module and said sample module, and for carrying power to said sample module from said base module; and    means for automated delivery of a coupling fluid dispensed between said sample module and said sample site prior to optical sampling.    
     
     
         2 . The apparatus of  claim 1 , wherein said sample module further comprises: 
 an illumination source;    a first optic located between said illumination source and said sample site, wherein said first optic removes heat; and    a second optic located between said illumination source and said sample site, wherein said second optic contacts an area about said sample site and aids in mechanical stabilization of a collection optic, said collection optic being in close proximity to said sample site,    wherein said close proximity reduces specular reflectance.    
     
     
         3 . The apparatus of  claim 1 , said sample module further comprising: 
 a guide that is securely and removeably attached to said sample site, said guide continuously and/or periodically physically and optically locating said sample module relative to said sample site in a repeatable manner and with minimal disturbance to said sample site.    
     
     
         4 . The apparatus of  claim 3 , further comprising means for: 
 pretreatment of said sample site sample module;    reduction of specular reflectance;    approaching and maintaining appropriate sample site temperature variation; and    minimizing sample site hydration changes.    
     
     
         5 . The apparatus of  claim 1 , wherein said sample module and said base module are integrated together into a handheld unit.  
     
     
         6 . The apparatus of  claim 1 , said sample module further comprising: 
 a heater for maintaining said sample site at a constant temperature.    
     
     
         7 . The apparatus of  claim 1 , wherein said base module either resides on a support surface or is worn by a person.  
     
     
         8 . The apparatus of  claim 1 , wherein said base module is coupled directly to said sample module, with said communication bundle forming an integral part thereof.  
     
     
         9 . The apparatus of  claim 1 , said illumination source comprising: 
 a tungsten halogen source ranging in power from about 0.05 to 5 Watts.    
     
     
         10 . The apparatus of  claim 1 , said illumination source comprising: 
 at least one light emitting diode.    
     
     
         11 . The apparatus of  claim 1 , said illumination source further comprising: 
 a reflector having any of a parabolic, elliptical, and spherical shape.    
     
     
         12 . The apparatus of  claim 1 , wherein said communication bundle is readily removed from said sample module, allowing said sample module to remain in close proximity with said sample site.  
     
     
         13 . The apparatus of  claim 1 , wherein said first optic comprises: 
 a silicon filter for removing light under 1050 nm, wherein a grating is used in the 1150 to 1850 nm region without detection of second or higher order light off of said grating,    wherein said silicon filter is placed before the grating.    
     
     
         14 . The apparatus of  claim 1 , wherein said first optic comprises any of: 
 a filter that is a silicon longpass optic;    a filter that is coated to block light from 1900 to 2500 nm;    a filter that is antireflection-coated to match refractive indices and increase light throughput;    a filter used in combination with a shortpass filter;    a filter that is coated with a blocker for removing a largest intensity of a black body curve of a typical tungsten halogen source that is not blocked by silicon, wherein said blocking band covers any region from about 1800 to 3000 nm; and    a filter that is used in combination with an RG glass that cuts off at about 2500 nm    a bandpass filter passing light from about 1100 to 2500 nm.    
     
     
         15 . The apparatus of  claim 1 , said sample module further comprising: 
 a Fabry-Perot interferometer.    
     
     
         16 . The apparatus of  claim 1 , said sample module comprising: 
 a surface defining an aperture for providing optical pathlengths within a sample for indirectly monitoring glucose concentrations within a body, providing acceptable energy delivery to said sample site, and providing appropriate heating/temperature control of said sample site;    wherein variation of said aperture affects a net analyte signal of a sampled tissue.    
     
     
         17 . The apparatus of  claim 1 , further comprising: 
 a fiber optic collection fiber placed in a center of an illumination area defined by an aperture.    
     
     
         18 . The apparatus of  claim 1 , further comprising: 
 means for performing an indirect determination of glucose from sample constituents which comprise any of: fat, protein, and water, wherein said sample constituents are distributed as a function of depth in a sample, wherein a magnitude of an indirect signal varies with said aperture.    
     
     
         19 . The apparatus of  claim 1 , wherein said sample module is semi-permanently attached to said sample site with a replaceable adhesive.  
     
     
         20 . The apparatus of  claim 1 , wherein said second optic provides a hydration barrier of said sample site.  
     
     
         21 . The apparatus of  claim 1 , sample module further comprising means for treating said sample site with any of: 
 photonic stimulation;    ultrasound pretreatment;    mechanical stimulation;    cooling; and    heating.    
     
     
         22 . The apparatus of  claim 1 , further comprising: 
 a wavelength axis standardization algorithm operating on said apparatus for use on a near-infrared spectrum collected using said apparatus, wherein said standardization algorithm uses a comparative analysis of at least a portion of said spectrum collected on said analyzer and at least one of:    a reference spectrum; and    known characteristics of said spectrum collected on said analyzer, wherein said standardization algorithm operates between instruments and through time.    
     
     
         23 . The apparatus of  claim 1 , further comprising: 
 means for using any of a signal and an absence of observed intensity at large water absorbance bands about 1450, 1900, and 2500 nm to determine when said sample module is in close proximity with a sample site surface.    
     
     
         24 . The apparatus of  claim 1 , wherein said base module further comprises: 
 a two-way wireless communication system for transferring data between said sample module and any of said base module and a data collection/processing system.    
     
     
         25 . The apparatus of  claim 1 , said sample module further comprising at least one of: 
 a low profile sample interface;    a low wattage stabilized source in close proximity to said sampled site;    a preheated interfacing solution;    means for maintaining a temperature controlled skin sample; and    a mechanism for constant pressure and/or displacement of sampled skin tissue.    
     
     
         26 . The apparatus of  claim 1 , further comprising: 
 means for measuring a reference spectrum and a wavelength standardization spectrum through spectroscopic measurement of a minimally absorbing substance and a material with known and immutable spectral absorbance bands.    
     
     
         27 . The apparatus of  claim 1 , said base module further comprising: 
 means for bias correcting one or more of spectra (X) and glucose concentration data (Y).    
     
     
         28 . The apparatus of  claim 1 , said base module further comprising: 
 means for calibrating to an individual or a group of individuals based upon a calibration data set comprised of paired data points of processed spectral measurements and reference biological parameter values.    
     
     
         29 . The apparatus of  claim 28 , wherein said reference values comprise at least one of the following: 
 finger capillary blood glucose concentrations;    alternate site capillary blood glucose concentrations at a site on the body other than the finger;    interstitial glucose concentrations; and    venous blood glucose concentrations.    
     
     
         30 . The apparatus of  claim 1 , wherein said base module is integrally connected to a docking station, wherein said docking station comprises a computer and a glucose management center; wherein said glucose management center keeps track of events occurring in time comprising any of glucose intake, insulin delivery, and determined glucose concentration.  
     
     
         31 . The apparatus of  claim 1 , said base module further comprising: 
 means for estimating precision of measurement through a statistical analysis of repeated or successive measurements; and    means for determining when a biological parameter is close to a preset level through a statistical estimate of confidence limits of a future analyte prediction.    
     
     
         32 . The apparatus of  claim 1 , said base module further comprising: 
 means for determining when a biological parameter is close to a preset level, wherein an alarm is invoked if an associated preset alarm level is within a confidence interval of a future biological parameter prediction.    
     
     
         33 . The apparatus of  claim 1 , further comprising: 
 means for taking any of continuous and semi-continuous measurements when said sample module is in proximate contact with said sample site.    
     
     
         34 . The apparatus of  claim 1 , said base module further comprising: 
 means for using time based information and trends to perform functions comprising any of:    estimate of precision;    determination of a confidence interval; and    prediction of a future event.    
     
     
         35 . The apparatus of  claim 1 , further comprising: 
 a link provided to an insulin delivery system to provide a feedback mechanism for control purposes.    
     
     
         36 . The apparatus of  claim 1 , said sample module further comprising: 
 a spectrometer system comprising light emitting diodes to provide near-infrared radiation to said sample site over predefined wavelength ranges, wherein each of said light emitting diodes provides near-infrared radiation over a band of wavelengths.    
     
     
         37 . The apparatus of  claim 36 , wherein said light emitting diodes are sequentially energized one at a time and/or in groups to obtain various estimates of diffuse reflectance of various tissue volumes at specific wavelengths or bands of wavelengths.  
     
     
         38 . The apparatus of  claim 36 , wherein said light emitting diodes are pulsed to provide short measurements with high signal-to-noise ratios to provide greater illumination intensity while avoiding photo heating of a sampled tissue volume.  
     
     
         39 . The apparatus of  claim 22 , wherein said reference spectrum comprises a spectrum of a standardized material.  
     
     
         40 . The apparatus of  claim 1 , wherein said coupling fluid is preheated.  
     
     
         41 . The apparatus of  claim 1 , wherein said coupling fluid is dispensed between said sample module and said sample site.