Tissue chromophore measurement system

A method of measuring a relative concentration of a first form of a chromophore in a tissue sample, said chromophore comprising at least a first form and a second form, comprising the steps of:

• (a) obtaining spectral data for said tissue sample over a plurality of wavelengths within a wavelength range within which the first and second forms of the chromophore provide an overlapping spectral response to irradiation with spectroscopic radiation;
• (b) determining a first 2d derivative spectrum value of the spectral data at a first wavelength within said wavelength range at which the first 2d derivative spectrum value varies with the relative concentration of the first form of the chromophore;
• (c) determining a second 2d derivative spectrum value of the spectral data at a second wavelength within said wavelength range at which the first 2d derivative spectrum value varies with the relative concentration of the first for-m of the chromophore;
• (d) deriving a scaled, 2d derivative spectrum value from information comprising the first and second 2d derivative spectrum values;
• (e) determining the relative concentration of the first form of the chromophore in the tissue sample from information comprising the scaled, 2d derivative spectrum value and a correlation which provides the relative concentration of the first form of the chromophore as a function of the scaled, 2d derivative spectrum value.

A system for measuring a relative concentration of a first form of a chromophore in a tissue sample, said chromophore comprising at least a first form and a second form, comprising:

• (a) a memory comprising data representative of a correlation which provides the relative concentration of the first form of the chromophore as a function of a scaled, 2d derivative spectrum value input, wherein the scaled second derivative value input is derived from a spectral response obtained from the tissue sample at a plurality of wavelengths within a wavelength range from 600 nm to 900 nm;
• (b) a light source assembly for generating spectroscopic radiation for irradiating the tissue sample;
• (c) a spectroscopic detector for detecting the spectral response emitted by the tissue sample responsive to irradiation with the spectroscopic radiation;
• and
• (d) a control system interfaced with the memory and the spectroscopic detector such that:
• the control system generates the scaled, second derivative spectrum value of the tissue sample from information comprising the spectral response of the tissue sample;
• and
• (ii) the control system generates information representative of the relative concentration of the first form of the chromophore in the tissue sample from information comprising the scaled, second derivative spectrum value and the correlation provided in the memory.