System and method for measuring absolute oxygen saturation

A system for determining concentrations of chromophores in a physiological medium, comprising:

• 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.

A system for determining concentrations of chromophores in a physiological medium, comprising:

• 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

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:

• 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.

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=βnγIo,mexp{−BmnLmnδΣi(εiCi)+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, αm is a parameter associated with the m-th wave source and the medium, βn 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, ε1 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 αm, βn, 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 ε1, following the step of eliminating.

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=αmβnγIo,mexp{−BmnLmnδΣ1(ε1C1)+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, αm is a parameter associated with at least one of said m-th wave source and medium, βn 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, ε1 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 αm, βn, 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.