Methods and apparatus for spectroscopic calibration model transfer
First Claim
1. A quantitative analysis instrument for measuring an unknown attribute level based on an indirect measurement of a biological sample, said instrument comprising:
- (a) a source of infrared energy generating multiple wavelengths;
(b) an input sensor element for directing said wavelengths of infrared energy into said biological sample and an output sensor element for collecting at least a portion of the diffusely reflected infrared energy from said biological sample, said input and said output sensor elements adapted to optically couple to said biological sample;
(c) at least one detector arranged for measuring the intensities of at least a portion of said wavelengths collected by said output sensor element;
(d) a memory device including master calibration information taken using one or more other instruments which has been developed in a manner that reduces instrument-specific attributes, reference measurement information from said instrument, and indirect measurement information from said instrument; and
(e) electronics for processing said master calibration information, said reference measurement information, and said indirect measurement information to generate a prediction of said unknown attribute level.
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Abstract
A method and apparatus for measuring a biological attribute, such as the concentration of an analyte, particularly a blood analyte in tissue such as glucose. The method utilizes spectrographic techniques in conjunction with an improved instrument-tailored calibration model. In a calibration phase, calibration model data is modified to reduce or eliminate instrument-specific attributes, resulting in a calibration data set modeling intra-instrument variation. In a prediction phase, the prediction process is tailored for each target instrument separately using a minimal number of spectral measurements from each instrument.
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Citations
71 Claims
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1. A quantitative analysis instrument for measuring an unknown attribute level based on an indirect measurement of a biological sample, said instrument comprising:
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(a) a source of infrared energy generating multiple wavelengths;
(b) an input sensor element for directing said wavelengths of infrared energy into said biological sample and an output sensor element for collecting at least a portion of the diffusely reflected infrared energy from said biological sample, said input and said output sensor elements adapted to optically couple to said biological sample;
(c) at least one detector arranged for measuring the intensities of at least a portion of said wavelengths collected by said output sensor element;
(d) a memory device including master calibration information taken using one or more other instruments which has been developed in a manner that reduces instrument-specific attributes, reference measurement information from said instrument, and indirect measurement information from said instrument; and
(e) electronics for processing said master calibration information, said reference measurement information, and said indirect measurement information to generate a prediction of said unknown attribute level. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A quantitative analysis instrument for measuring an unknown attribute level based on an indirect measurement of tissue, said instrument comprising:
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(a) a source of infrared energy generating multiple wavelengths;
(b) an input sensor element for directing said wavelengths of infrared energy into said tissue and an output sensor element for collecting at least a portion of the diffusely reflected infrared energy from said tissue, said input and said output sensor elements adapted to optically couple to the surface of said tissue;
(c) at least one detector arranged for measuring the intensities of at least a portion of said wavelengths collected by said output sensor element;
(d) a memory device including master calibration information taken from one or more other instruments which has been developed in a manner that reduces instrument-specific attributes, reference measurement information from said instrument, and indirect measurement information from said instrument; and
(e) electronics for processing said master calibration information, said reference measurement information, and said indirect measurement information to generate a prediction of said unknown attribute level. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A quantitative analysis instrument for non-invasive measurement of a biological attribute in human tissue, said instrument comprising:
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(a) a source of multiple wavelengths of infrared energy;
(b) an input element for directing said wavelengths of infrared energy into said tissue and an output element for collecting at least a portion of the diffusely reflected infrared energy from said tissue, said input and said output elements adapted to optically couple to the surface of said tissue;
(c) at least one detector for measuring the intensities of at least a portion of said wavelengths collected by said output element; and
(d) electronics for processing said measured intensities and indicating a value for said biological attribute, said electronics including a processing method incorporated therein, said method utilizing calibration data taken from one or more other instruments which has been developed in a manner that reduces instrument-specific spectral attributes;
said method utilizing one or more reference measurements from said instrument.- View Dependent Claims (14, 15, 16, 17, 18)
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19. A method for generating a prediction result of a biological attribute on a slave instrument using spectroscopy as a surrogate indirect measurement for a direct measurement of said biological attribute, said method comprising the steps of:
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(a) using a calibration model developed by using calibration data from at least one master instrument that was modified to reduce the spectral variation due to instrument-specific attributes; and
(b) using a prediction process to predict an unknown amount of said biological attribute in a target spectroscopic measurement made with said slave instrument, said prediction process utilizing said model in conjunction with one or more reference measurements. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 44)
determining P0 and Gref according to the method of claim 22 once with said specific instrument at a relatively high level of said physical characteristic and once with said specific instrument at a relatively low level of said physical characteristic; and
determining a scale factor based on P0 and Gref at said high and low levels.
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35. A method of generating a calibration model that is essentially free from instrument-specific effects comprising building a model by:
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(a) making a series of indirect measurements with a number of instruments, and making a direct measurement for at least some of said corresponding indirect measurements;
(b) calculating a mean indirect measurement and a mean direct measurement for each instrument based on the number of measurements from each instrument;
(c) meancentering the indirect measurements by subtracting said mean indirect measurement of each instrument from each indirect measurement, and meancentering said direct measurement by subtracting said mean direct measurement from each direct measurement of each instrument; and
(d) forming a calibration model from said meancentered direct and indirect measurements. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43, 45)
(a) making a direct measurement, Gref, and at least one indirect measurement Yref, using said specific instrument;
(b) using the generic calibration model with Yref to obtain a raw prediction, P0, of a physical characteristic.
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42. The method of claim 41, further comprising:
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making a plurality of indirect measurements using said specific instrument, Ynew;
using said generic calibration model with Ynew to obtain an untailored prediction, Pnew; and
predicting a physical characteristic Gnew for the instrument as a function of Pnew, P0, and Gref.
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43. The method of claim 42, wherein Gnew is a function of a known scale factor.
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45. The method of claim 41, wherein said measurements are made on a single measurement device, whereby said generic calibration model is to be utilized in said single measurement device.
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46. A method for generating a prediction result of a biological attribute on a slave instrument using spectroscopy as a surrogate indirect measurement for a direct measurement of said biological attribute, said method comprising the steps of:
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(a) using a modified calibration data set derived from calibration data taken from one or more master instruments processed in a manner that reduces the spectral variation due to instrument-specific attributes;
(b) generating a calibration model through application of a multivariate algorithm that uses a composite calibration data set formed by combining the modified calibration data with one or more reference measurements; and
(c) predicting an unknown amount of said biological attribute in a target spectroscopic measurement utilizing said calibration model. - View Dependent Claims (47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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58. A method for predicting a measure of a biological attribute on a slave instrument by effectively using master calibration data, the method comprising:
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(a) using calibration data obtained from at least one master instrument, wherein said calibration data has been modified to reduce variations due to instrument-specific attributes generating calibration data with reduced instrument specific spectral attributes;
(b) obtaining at least one indirect measurement with the slave instrument and a corresponding direct measurement;
(c) developing a prediction process that utilizes said master calibration data and said slave reference measurement; and
(d) using said prediction process to predict a measure of the unknown attribute in an indirect measurement made on said slave instrument. - View Dependent Claims (59, 60, 61, 62, 63, 64, 65, 66, 67)
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68. A non-invasive method for measuring a biological attribute in human tissue comprising the steps of:
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(a) providing an instrument for measuring infrared absorption, said instrument including an energy source emitting infrared energy at multiple wavelengths operatively connected to an input element, said instrument further including an output element operatively connected to a spectrum analyzer;
(b) coupling said input and output elements to said human tissue;
(c) irradiating said tissue through said input element with multiple wavelengths of infrared energy with resulting attenuation of at least some of said wavelengths;
(d) collecting at least a portion of the non-absorbed infrared energy with said output element followed by determining the intensities of said wavelengths of the collected infrared energy; and
(e) predicting the biological attribute in said measured intensities by utilizing calibration information, obtained on at least one master instrument and modified to reduce between instrument differences, at least one reference measurement from said specific instrument, and a multivariate processing method.
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69. A method for predicting a variable, comprising:
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(a) obtaining a calibration data set of direct measurements and indirect spectral measurements of the variable from at least one master instrument, wherein the calibration data set has been modified to reduce variations therein due to instrument-specific attributes for each master instrument;
(b) developing an instrument-specific calibration model from said modified calibration data set tailored for a specific instrument with at least one reference measurement of the variable from the specific instrument;
(c) obtaining at least one indirect measurement of the variable for the specific instrument; and
(d) using said instrument-specific calibration model and said at least one indirect measurement of the variable for the specific instrument to predict a measure of said variable in said specific instrument. - View Dependent Claims (70, 71)
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Specification