Patent ID: 8121671

Claim:
A method of determining a tissue state of the tissue of an individual, comprising: (a) illuminating a portion of the tissue of the individual with excitation light; (b) detecting light emitted from the tissue by fluorescence of a chemical within the tissue such that light that has interacted with the dermis is preferentially detected relative to light from other layers within the tissue, wherein detecting light emitted from the tissue comprises: (i) determining a first tissue reflectance characteristic at an excitation light wavelength; (ii) detecting light returned from the tissue in response to illumination at the excitation wavelength such that light that has interacted with the dermis is preferentially detected relative to light that has not interacted with the dermis; (iii) determining a corrected fluorescence measurement from the detected light and the first tissue reflectance characteristic; (c) determining the tissue state from the detected light and a model relating fluorescence and a tissue state, wherein determining a tissue state comprises determining the tissue state from the corrected fluorescence measurement and a model relating fluorescence and tissue state.