Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Patent
1997-06-11
2000-05-09
Dvorak, Linda C. M.
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
600322, A61B 500
Patent
active
060615826
DESCRIPTION:
BRIEF SUMMARY
The invention described in this application has been developed in part with funds received from the US National Institutes of Health under grant number DK 45126. The United States Government may have certain rights under this invention.
BACKGROUND OF THE INVENTION
This application relates to a method and apparatus for the non-invasive, quantitative measurement of physiological chemicals, particularly glucose, in a patient.
Determination of blood glucose is a routine procedure performed several times a day by many diabetics. In general, this procedure involves the taking of a small blood sample and evaluating the level of glucose in the sample. Common instruments used for this purpose use the enzyme glucose oxidase to convert glucose and oxygen to gluconic acid and hydrogen peroxide, and then measure the level of peroxide by either spectroscopic or electrochemical means.
While these daily measurements provide the diabetic patient with the ability to self-monitor and thus better control blood glucose levels, they are not without draw-backs. In particular, the taking of blood samples several times a day can be painful and exposes the patient to a risk of infection. Moreover, using this existing technology it is impossible to obtain a continuous blood glucose measurement. Thus, during the night, a patient must either be awakened periodically for testing or run the risk that glucose levels will drop to dangerous levels as they sleep.
In view of the foregoing, there exists a real need for a non-invasive method of measuring blood glucose in a patient. It has been suggested that this could be accomplished using near-infrared (NIR) radiation. Thus, U.S. Pat. No. 5,086,229 of Rosenthal, which is incorporated herein by reference, describes a system using a plurality of infrared light emitting diodes and a detector to measure blood glucose. The infrared measurement of glucose in the body is immensely complicated, however, because of the substantial absorbances of fats and proteins in the near-infrared. Thus, while the Rosenthal patent presents an interesting theory, there is no published documentation that demonstrates the ability of the Rosenthal system to measure glucose noninvasively. Furthermore, the wavelengths used in the Rosenthal system have never been shown to possess useful glucose information.
It is an object of the present invention to provide a practically useful non-invasive near-infrared detector for blood glucose and other physiological chemicals that is adaptable for continuous use.
It is a further object of the present invention to provide a method for the non-invasive quantitative measurement of physiological chemicals and particularly glucose in a patient that can be used either continuously or intermittently.
It is still a further object of the invention to provide an apparatus for continuous or intermittent non-invasive monitoring of blood glucose and other physiological chemicals in a patient.
SUMMARY OF THE INVENTION
In accordance with the invention, non-invasive measurements of physiological chemicals such as glucose are made using infrared radiation and a signal processing system that permits the construction of a device suited for home use. Thus, the level of a selected physiological chemical in a test subject is determined in a non-invasive and quantitative manner by a method comprising the steps of: such that the radiation is transmitted through or reflected from the test subject; radiation using a detector; indicative of the physiological chemical; and applying a defined mathematical model to the digitally filtered data. The data collected may be in the form of an absorbance spectrum, i.e., a representation of the variation in absorbance as a function of wavelength; or in the form of an interferogram, i.e., a representation of infrared light intensity as a function of the retardation of the moving mirror in the interferometer, and thus of time.
In a further aspect of the invention, there is provided a device for measurement of a chemical in a sample comprising: transmitted through o
REFERENCES:
patent: 5372135 (1994-12-01), Mendelson et al.
patent: 5459317 (1995-10-01), Small et al.
Arnold et al., "Determination of Physiological Levels of Glucose in an Aqueous Matrix with Digitally Filtered Fourier Transformed Near-Infrared Spectra," Analyticl Chemistry 62, 1457-1464, 1990.
Small et al., "Design of Optimized Finite Impulse Response Digital Filters for Use with Passive Fourier Transform Infrared Interferograms", Analytical Chemistry 62, 1768-1777, 1990.
Arnold Mark
Small Gary W.
Dvorak Linda C. M.
Ohio University
University of Iowa Research Foundation
Yarnell Bryan K.
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