Monitoring blood constituent levels in biological tissue
First Claim
1. An apparatus for non-invasively measuring blood constituent levels within biological tissue, the apparatus comprising:
- at least one light source for providing a sample beam and a reference beam, the at least one light source providing at least two wavelengths of light, the at least one light source configured to direct the sample beam to the biological tissue, the at least two wavelengths of light including first and second wavelengths of light, the first wavelength of light having measurably different scattering properties sensitive to a first blood constituent relative to the second wavelength of light;
a phase shifter configured to adjust phase path of the reference beam;
a scanner configured to scan the sample beam over an area of the subject'"'"'s tissue;
an interferometer that allows comparison of a reflected sample beam from the subject tissue with the reference beam;
at least one photodetector configured to generate non-image measurements from the reference beam and the reflected sample beam, the non-image measurements including at least scatter measurements of the first and second wavelengths of light; and
blood constituent monitor configured to receive the non-image measurements and calculate, based on the non-image measurements, a level of a first blood constituent based at least partly on the scatter measurements of the first wavelength of light obtained at a location in the biological tissue where the scatter measurements of the second wavelength of light indicate a presence of blood-perfused tissue.
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Accused Products
Abstract
In accordance with the invention, a low coherence interferometer is used to non-invasively monitor the concentration of glucose in blood by shining a light over a surface area of human or animal tissue, continuously scanning the light over a two dimensional area of the surface, collecting the reflected light from within the tissue and constructively interfering this reflected light with light reflected along a reference path to scan the tissue in depth. Since the reflection spectrum is sensitive to glucose concentration at particular wavelengths, measurement and analysis of the reflected light provides a measure of the level of glucose in the blood. The measurement of glucose is taken from multiple depths within blood-profused tissue, and sensitivity is preferably enhanced by the use of multiple wavelengths. Noise or speckle associated with this technique is minimized by continuously scanning the illuminated tissue in area and depth.
898 Citations
22 Claims
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1. An apparatus for non-invasively measuring blood constituent levels within biological tissue, the apparatus comprising:
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at least one light source for providing a sample beam and a reference beam, the at least one light source providing at least two wavelengths of light, the at least one light source configured to direct the sample beam to the biological tissue, the at least two wavelengths of light including first and second wavelengths of light, the first wavelength of light having measurably different scattering properties sensitive to a first blood constituent relative to the second wavelength of light; a phase shifter configured to adjust phase path of the reference beam; a scanner configured to scan the sample beam over an area of the subject'"'"'s tissue; an interferometer that allows comparison of a reflected sample beam from the subject tissue with the reference beam; at least one photodetector configured to generate non-image measurements from the reference beam and the reflected sample beam, the non-image measurements including at least scatter measurements of the first and second wavelengths of light; and blood constituent monitor configured to receive the non-image measurements and calculate, based on the non-image measurements, a level of a first blood constituent based at least partly on the scatter measurements of the first wavelength of light obtained at a location in the biological tissue where the scatter measurements of the second wavelength of light indicate a presence of blood-perfused tissue. - View Dependent Claims (2, 3, 4)
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5. A system for non-invasively monitoring blood constituent level within biological tissue, the system comprising:
one or more processors configured to; initiate scanning by an interferometric sensor of an area of biological tissue with light including first and second wavelengths, the first wavelength of light having measurably different scattering properties sensitive to a first blood constituent relative to the second wavelength of light; receive non-image measurements from the interferometric sensor for at least one tissue depth, the non-image measurements including at least scatter measurements of the first and second wavelengths of light at the at least one tissue depth; and in response to determining, based on the scatter measurements of the second wavelength of light at the at least one tissue depth, a tissue location indicative of a presence of blood-perfused tissue, determine a level of the first blood constituent within the biological tissue based at least partly on the scatter measurements of the first wavelength of light obtained at the tissue location. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for non-invasively monitoring blood constituent level within biological tissue, the method comprising:
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initiating scanning by an interferometric sensor of an area of biological tissue with light including first and second wavelengths, the first wavelength of light having measurably different scattering properties sensitive to a first blood constituent relative to the second wavelength of light; receiving light measurements from the interferometric sensor for at least one tissue depth, the light measurements including at least scatter measurements of the first and second wavelengths of light at the at least one tissue depth; and without generating an image from the light measurements and in response to determining, based on the scatter measurements of the second wavelength of light at the at least one tissue depth, a tissue location indicative of a presence of blood-perfused tissue, determining a level of the first blood constituent within the biological tissue based at least partly on the scatter measurements of the first wavelength of light obtained at the tissue location. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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Specification