Method and apparatus for noninvasive measurement of blood glucose by photoacoustics
First Claim
1. An apparatus for determining a concentration of a component in a subcutaneous bodily fluid, comprising:
- a source for irradiating a portion of a subcutaneous bodily fluid by heat-diffusion to generate acoustic energy propagating in a medium over a surface of said subcutaneous bodily fluid in response to said irradiation;
a detector comprising a measuring cell and a reference cell for detecting said acoustic energy and providing an acoustic signal in response to said acoustic energy; and
a processor for determining a concentration of a component in said subcutaneous bodily fluid in response to said acoustic signal and characteristics of said component.
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Accused Products
Abstract
A method and apparatus for noninvasively measuring blood glucose levels provides an indirect, reagentless, differential, photoacoustic technique which responds to absorption in a thin surface layer. An excitation source provides electromagnetic energy which is utilized to irradiate the tissue, such as skin. The output of the radiation of the excitation source at the desired wavelength is coupled through a transmission device, such as a fiber optic bundle, which irradiates the electromagnetic energy onto the body surface. Upon irradiation, acoustic energy is generated by the absorption of the electromagnetic energy in a relatively thin layer of the sample to be measured, characterized by a heat-diffusing length. The acoustic energy is detected by the probe which includes a measuring cell, reference cell, window and differential microphone. Absorption of the light beam results in periodic heating of the tissue, at and near the tissue surface. The air in contact with the tissue surface in the measuring cell is in turn heated, and produces an acoustic emission in the measuring cell. This acoustic emission is detected with the differential microphone, one end of which is positioned in the measuring cell and the other end of which is positioned in the reference cell. A processor determines the concentration of the substance based upon the detected acoustic signal.
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Citations
57 Claims
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1. An apparatus for determining a concentration of a component in a subcutaneous bodily fluid, comprising:
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a source for irradiating a portion of a subcutaneous bodily fluid by heat-diffusion to generate acoustic energy propagating in a medium over a surface of said subcutaneous bodily fluid in response to said irradiation; a detector comprising a measuring cell and a reference cell for detecting said acoustic energy and providing an acoustic signal in response to said acoustic energy; and a processor for determining a concentration of a component in said subcutaneous bodily fluid in response to said acoustic signal and characteristics of said component. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for determining a concentration of a component in a subcutaneous bodily fluid, comprising the steps of:
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irradiating a portion of subcutaneous bodily fluid by heat-diffusion to generate acoustic energy propagating in a medium over a surface of said subcutaneous bodily fluid in response to said irradiation; measuring said acoustic energy generated in response to said irradiating step and providing a measured acoustic signal in response to said measured acoustic energy; detecting reference acoustic energy and providing a reference acoustic signal in response to said reference acoustic energy; measuring a difference in acoustic response between said measured acoustic signal and said reference acoustic signal; and determining a concentration of a component in said subcutaneous bodily fluid in response to said measuring and reference acoustic signals, said difference, and characteristics of said component. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. The method claimed in 16, filler comprising the step of:
transmitting said irradiation from said source to said subcutaneous bodily fluid utilizing a guide. - View Dependent Claims (28)
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29. An apparatus for measuring a concentration of an analyte in a subcutaneous bodily fluid, comprising:
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means for providing electromagnetic energy at wavelengths corresponding to the absorption characteristics of an analyte to excite a portion of subcutaneous bodily fluid by heat-diffusion to generate acoustic energy propagating in a medium over a surface of said subcutaneous bodily fluid in response to said excitation; first detecting means for detecting said acoustic energy and providing a first acoustic signal in response to said acoustic energy; second detecting means for detecting noise and providing a second acoustic signal in response to said noise; means for measuring the difference in acoustic response of said first detecting means and said second detecting means; and means for determining a concentration of said analyte in response to said first acoustic signal, said second acoustic signal, said difference, and an absorption spectrum of said analyte. - View Dependent Claims (30, 31)
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32. A method of measuring a concentration of an analyte in a subcutaneous bodily fluid, comprising the steps of:
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providing electromagnetic energy at wavelengths corresponding to the absorption characteristics of an analyte to excite a portion of subcutaneous bodily fluid by heat-diffusion to generate acoustic energy propagating in a medium over a surface of said subcutaneous bodily fluid in response to said excitation; detecting said acoustic energy by a measuring cell and providing a first acoustic signal in response to said acoustic energy; detecting noise by a reference cell and providing a second acoustic signal in response to said noise; receiving said first acoustic signal from said measuring cell; receiving said second acoustic signal from said reference cell; measuring the difference in acoustic response from said measuring cell and said reference cell; and determining a concentration of said analyte in response to said first acoustic signal said second acoustic signal, said difference, and an absorption spectrum of said analyte. - View Dependent Claims (33, 34, 35)
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36. An apparatus for determining a concentration of glucose in a subcutaneous body part, comprising:
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a source for irradiating a portion of a subcutaneous body part by heat diffusion to generate acoustic energy propagating in air over a surface of said subcutaneous body part in response to said irradiation; a detector comprising a measuring cell and a reference cell for detecting said acoustic energy and providing an acoustic signal in response to said acoustic energy; and a processor for determining a concentration of glucose in said subcutaneous body art in response to said acoustic signal and characteristics of glucose. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
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48. A method for determining a concentration of glucose in a subcutaneous body part, comprising the steps of:
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irradiating a portion of a subcutaneous body part by heat-diffusion to generate acoustic energy propagating in air over a surface of said body part in response to said irradiation; detecting said acoustic energy by a measuring cell and providing a first acoustic signal in response to said acoustic energy; detecting noise by a reference cell and providing a second acoustic signal in response to said noise; receiving said first acoustic signal from said measuring cell; receiving said second acoustic signal from said reference cell; measuring the difference in acoustic response from said measuring cell and said reference cell; and determining a concentration of glucose in said subcutaneous body part in response to said first acoustic signal, said second acoustic signal, said difference, and characteristics of glucose. - View Dependent Claims (49, 50, 51, 52, 53, 54, 55, 56, 57)
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Specification