In vivo optical characterization of human tissues from 610 to 1010 nm by time-resolved reflectance spectroscopy

A fully automated system for time-resolved reflectance spectroscopy based o n tunable mode-locked laser sources and on time-correlated single-photon co unting for the detection of time-resolved reflectance data was applied to t he evaluation of the optical properties of biological tissues (arm, abdomen and forehead) in vivo from 610 to 1010 nm. The scattering decreases progre ssively with increasing wavelength, while the absorption line shapes show t he typical spectral features of the principal tissue components (haemoglobi n, water and lipid), with different weights depending on the tissue type. T he best fit of the absorption spectra measured in vivo with the spectra of the pure constituents yielded information on the percentage composition of the different tissues. The interpretation of transport scattering spectra w ith Mie theory provided information on tissue structure.