Optical spectroscopy pathlength measurement system
First Claim
1. A physiological monitor for measuring a blood constituent concentration within a tissue portion of a subject, said monitor comprising:
- a polarized light source adapted to illuminate said tissue portion with an incident light beam;
a magnetic field generator configured to impose a magnetic field on said tissue portion while illuminated by said light source, said magnetic field imparting a rotation in the plane of polarization of said incident light beam as it propagates through said tissue portion and emerges as a transmitted light beam;
a polarimeter having an input responsive to said transmitted light beam and an output corresponding to said rotation; and
a signal processor in communications with said polarimeter output so as to compute an output corresponding to a mean pathlength estimate of said tissue portion.
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Accused Products
Abstract
A physiological monitor utilizes Faraday rotation measurements to estimate mean photon pathlengths through tissue. These pathlength estimates, along with corresponding optical spectroscopy measurements allow the noninvasive monitoring of blood constituent concentrations. The technique is particularly applicable to noninvasive blood glucose measurements. The physiological monitor has a polarized light source for illuminating tissue and a magnetic field generator which creates a magnetic field within the tissue during illumination. The magnetic field imparts a Faraday rotation in the plane of polarization of the incident light beam as it propagates through the tissue and emerges as a transmitted light beam. A polarimeter is used to measure the rotation of the transmitted light. A signal processor then computes an estimate of the mean pathlength from the polarimeter output. The polarized light source has a multiple wavelength optical emitter and, in conjunction with the polarimeter detector, also functions as a spectrometer. The signal processor combines spectroscopic measurements at various wavelengths with corresponding mean pathlength estimates to compute blood constituent concentrations.
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Citations
18 Claims
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1. A physiological monitor for measuring a blood constituent concentration within a tissue portion of a subject, said monitor comprising:
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a polarized light source adapted to illuminate said tissue portion with an incident light beam;
a magnetic field generator configured to impose a magnetic field on said tissue portion while illuminated by said light source, said magnetic field imparting a rotation in the plane of polarization of said incident light beam as it propagates through said tissue portion and emerges as a transmitted light beam;
a polarimeter having an input responsive to said transmitted light beam and an output corresponding to said rotation; and
a signal processor in communications with said polarimeter output so as to compute an output corresponding to a mean pathlength estimate of said tissue portion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A physiological monitor for measuring a blood constituent concentration within a tissue portion of a subject, said monitor comprising:
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a light source adapted to illuminate said tissue portion with a monochromatic light polarized in a first direction;
a magnetic field generator configured to alternately impose a first magnetic field and a second magnetic field on said tissue portion while illuminated by said light, said first field imparting a first rotation on said light and said second field imparting a second rotation on said light; and
a detector responsive to light intensity polarized in a second direction, said detector providing a first output corresponding to said first rotation and a second output corresponding to said second rotation so as to compensate for scattering in said tissue portion when calculating a blood constituent concentration. - View Dependent Claims (11, 12, 13, 15, 16, 18)
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14. A physiological monitoring method for measuring a blood constituent concentration within a tissue portion of a subject, said method comprising the steps of:
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illuminating said tissue portion with a polarized light beam;
applying a magnetic field to said tissue portion;
measuring a rotation in polarization of said light beam after transmission through said tissue portion;
estimating a mean photon pathlength from said rotation; and
applying said mean pathlength to a spectroscopic measurement to determine said constituent concentration.
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17. A physiological monitor for measuring a blood constituent concentration within a tissue portion of a subject, said monitor comprising:
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a light source means for illuminating said tissue portion with a polarized light beam;
a generator means for imparting a rotation of said polarized light beam as it propagates through said tissue portion;
a detector means for outputting a measure of said rotation; and
a processor means for utilizing said measure to provide a compensation for scattering within said tissue portion.
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Specification