System and method for measuring absolute oxygen saturation
First Claim
1. A system for determining concentrations of chromophores in a physiological medium, comprising:
- a source module to irradiate into said medium at least two sets of electromagnetic radiation having different wave characteristics;
a detector module to detect electromagnetic radiation transmitted through said medium; and
a processing module operatively coupled with said detector module to determine an absolute value of at least one of said concentrations from electromagnetic radiation irradiated from and detected by said source and detector modules, wherein said determination is based only on intensity measurements of continuous wave electromagnetic radiation from the source module.
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Abstract
The present invention generally relates to apparatus and methods for obtaining absolute values of concentrations of chromophores of a medium and/or absolute values of their ratios. In particular, the present invention relates to continuous wave spectroscopic optical systems and methods for determining the absolute values of deoxygenated and/or oxygenated hemoglobins and their ratios in a physiological medium. The optical system typically includes (1) a source module optically coupling with the medium and irradiating into the medium multiple sets of electromagnetic waves with different wave characteristics, (2) a detector module optically coupling with the medium and detecting electromagnetic waves, and (3) a processing module operatively coupling with the detector module, and determining the absolute values of the concentrations and the ratios thereof from multiple wave equations applied to the source and detector modules. The processing module is designed to obtain such absolute values by a method typically including the steps of (1) obtaining multiple sets of wave equations, (2) eliminating source-dependent and detector-dependent parameters therefrom to obtain a set of intermediate equations, (3) providing a correlation between medium-dependent and geometry-dependent parameters and the chromophore concentrations or ratios thereof, (4) incorporating the correlation into the set of intermediate equations, and (5) obtaining the absolute values of the chromophore concentrations and ratios thereof.
31 Citations
55 Claims
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1. A system for determining concentrations of chromophores in a physiological medium, comprising:
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a source module to irradiate into said medium at least two sets of electromagnetic radiation having different wave characteristics;
a detector module to detect electromagnetic radiation transmitted through said medium; and
a processing module operatively coupled with said detector module to determine an absolute value of at least one of said concentrations from electromagnetic radiation irradiated from and detected by said source and detector modules, wherein said determination is based only on intensity measurements of continuous wave electromagnetic radiation from the source module. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A system for determining concentrations of chromophores in a physiological medium, comprising:
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one or more sources irradiating into said medium at least two sets of near-infrared electromagnetic waves having different wave characteristics;
one or more detectors detecting electromagnetic waves transmitted through said medium;
input means for entering input parameter data; and
a processing module determining absolute values of at least one of said concentrations, wherein said determination is not based on measuring phase characteristics of the electromagnetic radiation received from said one or more detectors, or the response of the medium to an electromagnetic impulse from said one or more sources.
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32. A system for determining concentrations of chromophores in a physiological medium, comprising:
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at least one source for irradiating into said medium at least two sets of electromagnetic waves having different wave characteristics;
at least one detector for detecting electromagnetic waves transmitted through said medium;
a processor coupled to the at least one detector computing one of;
absolute values of said concentrations and ratios of said concentrations,wherein said computation is based only on intensity measurements of continuous wave electromagnetic radiation from the source module
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33. A method for determining concentrations of chromophores in a physiological medium using a system having at least one wave source and at least one wave detector, wherein electromagnetic waves are irradiated by said wave source, transmitted through the physiological medium, and detected by said wave detector, the method comprising the steps of:
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irradiating at least two sets of electromagnetic waves having different wave characteristics to obtain a plurality of measurements;
providing a mathematical expression relating said plurality of measurements to parameters of the system, and parameters associated with said medium;
eliminating source-dependent and detector-dependent parameters from the provided mathematical expression; and
determining an absolute value of at least one of said concentrations, wherein said determination is based only on intensity measurements of continuous wave electromagnetic radiation and pre-determined chromophore-dependent parameters. - View Dependent Claims (34, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
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35. A method for determining concentrations of chromophores in a physiological medium using a system having at least one wave source and at least one wave detector by application of a wave equation having a form:
Imn=β
nγ
Io,mexp{−
BmnLmnδ
Σ
i(ε
iCi)+σ
},wherein Io,m is a variable representing an intensity of electromagnetic waves irradiated by the m-th wave source, Imn is a variable for an intensity of electromagnetic waves irradiated by the m-th wave source and detected by the n-th detector, α
m is a parameter associated with the m-th wave source and the medium, β
n is a parameter associated with the n-th wave detector and the medium, γ
is one of a proportionality parameter associated with at least one of wave source, detector, and medium, Bmn is a parameter accounting for lengths of optical paths of electromagnetic waves through said medium and associated with the m-th wave source, n-th wave detector, and the medium, Lmn is a parameter accounting for a distance between the m-th wave source and the n-th wave detector, δ
is one of a proportionality parameter associated with at least one wave source, wave detector, and medium, ε
1 is a parameter accounting for an optical interaction between electromagnetic waves and an i-th chromophore in said medium, C1 is a variable for concentration of said i-th chromophore, and C is one of a proportionality parameter associated with a wave source, wave detector, and medium, said method comprising the steps of;
irradiating a first and second set of electromagnetic waves having different wave characteristics and measuring signals received from the medium to obtain two sets of equations relating the measured signals with unknown parameters in the wave equation;
eliminating at least one of the parameters α
m, β
n, γ
, δ
, and σ
from the wave equation using the first and second set of equations to obtain a third set of equations;
obtaining an expression for an absolute value of at least one of said concentrations based on values associated with Imn, Io,m, and ε
1, following the step of eliminating.
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53. A method for determining concentrations of chromophores in a physiological medium using a system having at least one wave source and at least one wave detector using a mathematical expression having the form:
Imn=α
mβ
nγ
Io,mexp{−
BmnLmnδ
Σ
1(ε
1C1)+σ
},wherein Io,m is a variable representing an intensity of electromagnetic waves irradiated by an m-th wave source, Imn is a variable for an intensity of electromagnetic waves irradiated by said m-th wave source and detected by an n-th wave detector, α
m is a parameter associated with at least one of said m-th wave source and medium, β
n is a parameter associated with at least one of said n-th wave detector and medium, γ
is one of a proportionality constant and a parameter associated with at least one of said m-th wave source, n-th wave detector, and medium, Bmn is a parameter accounting for lengths of optical paths of electromagnetic waves through said medium and associated with at least one of said m-th wave source, n-th wave detector, and medium, Lmn is a parameter accounting for a distance between said m-th wave source and n-th wave detector, δ
is a one of a proportionality constant and a parameter associated with at least one of said m-th wave source, n-th wave detector, and medium, ε
1 is a parameter accounting for an optical interaction between electromagnetic waves and an i-th chromophore in said medium, Ci is a variable for concentration of said i-th chromophore, and σ
is one of a proportionality constant and a parameter associated with at least one of said m-th source, n-th detector, and medium, said method comprising the steps of;
irradiating a first and second set of electromagnetic waves having different wave characteristics and measuring signals received from the medium to obtain at least two sets of equations relating the measured signals with unknown parameters in the wave equation;
eliminating at least one of α
m, β
n, γ
, δ
, and σ
from the obtained wave equations;
defining parameters of the mathematical expression including Bmn and Lmn as a function of at least one of said concentrations; and
determining concentrations of chromophores in a physiological medium. - View Dependent Claims (54, 55)
Specification