Method for building an algorithm for converting spectral information

• US 9,554,735 B2
• Filed: 04/26/2013
• Issued: 01/31/2017
• Est. Priority Date: 02/11/2002
• Status: Active Grant

• Current Assignee: Ascensia Diabetes Care Holdings AG (PHC Holdings Corporation)
• Original Assignee: Ascensia Diabetes Care Holdings AG (PHC Holdings Corporation)
• Inventors: Rebec, Mihailo V., Smous, James E., Brown, Steven D., Tan, Hu-Wei
• Primary Examiner(s): Chen, Tse
• Assistant Examiner(s): Liu, Chu Chuan (JJ)
• Application Number:
  US13/871,116
• Publication Number:
  US 20130261406A1
• Time in Patent Office: 1,376 Days
• Field of Search: 600/310, 600/316, 600/322, 600/331, 600/365, 600/473, 436/8, 436/14, 436/164, 356/39
• US Class Current: 1/1
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 2201/067 Electro-optic, magneto-optic, acousto-optic elements

Abstract

A system for determining the concentration of an analyte in at least one body fluid in body tissue comprises an infrared light source, a body tissue interface, a detector, and a central processing unit. The body tissue interface is adapted to contact body tissue and to deliver light from the infrared light source to the contacted body tissue. The detector is adapted to receive spectral information corresponding to infrared light transmitted through the portion of body tissue being analyzed and to convert the received spectral information into an electrical signal indicative of the received spectral information. The central processing unit is adapted to compare the electrical signal to an algorithm built upon correlation with the analyte in body fluid, the algorithm adapted to convert the received spectral information into the concentration of the analyte in at least one body fluid.

Claims

1. A method for converting spectral information obtained from a body tissue into an analyte concentration level in at least one body fluid in the body tissue, wherein the analyte concentration level of the at least one body fluid in body tissue of a plurality of test subjects including a first test subject and a second test subject is modulated to a plurality of predetermined analyte concentration levels within a range of analyte concentration levels, the method comprising the acts of:

invasively determining the analyte concentration levels of the at least one body fluid of each of the test subjects during an analyte clamping test comprising the modulating of analyte concentration levels of the at least one body fluid in body tissue;

directing by an infrared light source infrared light onto the body tissue of the test subjects being analyzed during the analyte clamping test;

collecting spectral information using a detector from the body tissue of the test subjects;

creating, using a spectrometer, modeled spectral information modeled for analyte concentration levels outside the range of analyte concentration levels;

combining the modeled spectral information with the collected spectral information from the body tissue of the test subjects;

normalizing the combined spectral information;

combining by a central processing unit a portion of the normalized spectral information collected from the first test subject with a portion of the normalized spectral information collected from the second test subject to create a combined spectral data set;

the central processing unit mean centering the combined spectral data set;

the central processing unit creating a partial least squares regression model having at least one orthogonal signal correction component from the combined spectral data set, the partial least squares regression model being configured to filter out non-analyte related spectral information from the spectral data set by selecting wavelengths in the spectral data set based on at least changes in a refractive index of body tissue due to changes in tissue concentration;

the central processing unit applying an orthogonal signal correction analysis to the normalized spectral information collected from the first test subject, thereby forming a first corrected data set, and to the normalized spectral information collected from the second test subject, thereby forming a second corrected data set;

the central processing unit applying the partial least squares regression model to the first corrected data set, resulting in a calibration algorithm that is applied to the second corrected data set, and predicting using the calibration algorithm an analyte concentration level in a body fluid in a body tissue of the second test subject based upon the collected spectral information obtained from the body tissue of the second test subject, wherein the analyte is glucose.

2. The method of claim 1, wherein the analyte level concentration in the body fluid in the body tissue of the second test subject is predicted by applying the partial least squares regression model to the second corrected data set.

3. The method of claim 2 further comprising comparing the predicted analyte concentration levels of the at least one body fluid in the body tissue of the second test subject to the invasively determined the analyte concentration levels collected from the second test subject during the test.

4. The method of claim 1 further comprising filtering the first and the second corrected spectral data set by applying a wavelet analysis prior to applying the partial least squares regression model.

5. The method of claim 1 further comprising collecting data other than spectral information during the modulating of analyte concentration levels, the data being selected from the group consisting of a target body fluid analyte concentration for each test subject, temperature of the body tissue for each test subject, pressure applied to the body tissue of each test subject, frequency of the infrared light directed onto the body tissue of each test subject, and time of data collection.