title: Depth profile of diffuse reflectance near-infrared spectroscopy for measurement of water content in skin.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan. arimoto-h@aist.go.jp
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Arimoto
authors.forename: Mariko
authors.initials: M
authors.lastname: Egawa
authors.forename: Yukio
authors.initials: Y
authors.lastname: Yamada
mesh_terms: D000042:Absorption; D000465:Algorithms; D001834:Body Water / Q000378:metabolism*; D003198:Computer Simulation; D006801:Humans; D008027:Light; D008954:Models, Biological; D009010:Monte Carlo Method; D055095:Optics and Photonics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012879:Skin Physiological Phenomena; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D014867:Water / Q000032:analysis* / Q000378:metabolism*
chemical_list: D014867:Water