Systems and methods for measuring oxygenation

A method for measuring a tissue parameter in a tissue sample, said method comprising:

• receiving first and second scattered light intensity signals at unique locations on a selected region of tissue from light injected into said region of tissue from a light source to identify a measured light attenuation data value;
• accessing an electronic data store comprising simulated light attenuation data determined from a mathematical tissue model at discrete points over a range of two or more tissue parameters, and wherein said simulated light attenuation data are a function of one or more temperature-dependent light source spectra;
• determining said tissue parameter in said tissue sample by selecting a closest match between said measured light attenuation data and said simulated light attenuation data;
• and
• transmitting an electronic signal representative of said determined tissue parameter to an output register;
• wherein said selecting a closest match between said measured light attenuation data and said calculated light attenuation data comprises:
• determining a ratio value of said first and said second scattered light intensity signals from said light source;
• receiving a temperature measurement of said light source;
• generating a temperature-corrected set of light attenuation data by interpolating said calculated light attenuation data based on said measured temperature;
• finding the closest match of said temperature-corrected set of light attenuation data in said electronic data store;
• forming a Jacobian matrix that includes the partial derivatives of each temperature-corrected light attenuation data point with respect to each of said tissue parameter values at the closest-match sensor value;
• and
• solving the system of n equations and n unknowns provided by said Jacobian matrix and the residual values between said closest-match sensor value and said measured light intensity signal to yield a correction value that can be applied to said determined chromophore concentration to increase the precision of said measurement.

A computer program product, encoded on a non-transitory computer-readable medium, operable to cause one or more processors to perform operations for measuring a chromophore concentration in a tissue sample, comprising:

• receiving first and second scattered light intensity signals at unique locations on a selected region of tissue from light injected into said region of tissue from a light source to identify a measured light attenuation data value;
• accessing an electronic data store comprising calculated light attenuation data determined from a mathematical tissue model at discrete points over a range of two or more tissue parameters;
• wherein said chromophore is one of said parameters, and wherein said light attenuation data are a function of one or more temperature-dependent light source spectra and are determined in part by simulating a plurality of light ray paths launched from said light source into said region of tissue and detected at said unique tissue locations;
• wherein said simulated light attenuation data are calculated in part by integrating a modified Beer-Lambert equation over wavelength for each of said plurality of light ray paths for a given light source spectrum;
• determining said chromophore concentration in said tissue sample by selecting a closest match between said measured light attenuation data and said calculated light attenuation data;
• and
• transmitting an electronic signal representative of said determined chromophore concentration to an output register.

A system for measuring a tissue parameter in a tissue sample, comprising:

• a computer control system in signal communication with a remote sensing device, the remote sensing device comprising:
• a) a plurality of light sources operable to produce an output signal for each of said light sources successively, each of said output signals having a different spectral profile than the other of said output signals, wherein said plurality of light sources is cooperatively arranged with a light-transmitting medium that is configured to inject said output signals into said tissue sample at a selected injection area of said tissue sample;
• and
• b) two or more light detectors arranged substantially collinear with said light source, wherein a distance from said light source to a first of said detectors is about one-half the distance of said light source to a second, different one of said detectors, wherein each of said detectors is configured to receive said light signal after propagating through said tissue to measure an attenuated light value;
• wherein said control system is operable to initiate said measurement of said attenuated light signals;
• and
• wherein said computer control system comprises:
• a) a processor in signal communication with a data store comprising simulated light attenuation values determined from a mathematical tissue model at discrete points over a range of two or more tissue parameters;
• wherein said simulated light attenuation values are a function of one or more temperature-dependent variables of said light source spectra and are determined in part by simulating a plurality of light ray paths launched from said light source into said region of tissue and detected at said unique tissue locations;
• wherein said simulated light attenuation data are calculated in part by integrating a modified Beer-Lambert equation over wavelength for each of said plurality of light ray paths for a given light source spectrum;
• and
• b) an output register in signal communication with said processor configured to receive a processor-calculated tissue parameter value determined by selecting a closest match between said measured light attenuation value and said simulated light attenuation values.