BACKGROUND/PURPOSE: The penetration depth of light in diffuse reflectance near-infrared spectroscopy for measuring water content in skin is assessed both from theoretical and experimental points of view.

METHODS

The Monte Carlo simulation was implemented to investigate the dependencies of the light penetration depth on a source-detector distance. To compare with the simulation results, an in vivo experiment for water contents of skin was performed introducing two different optical fiber probes.

RESULTS

It is found that the minimum separation between a source and detector fibers influences largely the measurement depth. The larger separation leads to a deeper measurement depth at a particular wavelength. The measurement depth is also influenced fairly by the absorption coefficient of the tissue. The larger absorption coefficient results in a shallower measurement depth.

CONCLUSION

The correlations between the water contents measured by the optical and capacitance techniques were discussed. The dependencies of the light penetration depth on the source-detector geometry and wavelength are presented.