title: Imaging superficial tissues with polarized light.
abstract: OBJECTIVE
  Polarized light can be used to obtain images of superficial tissue layers such as skin, and some example images are presented. This study presents a study of the transition of linearly polarized light into randomly polarized light during light propagation through tissues.
  
  
  METHODS
  The transition of polarization was studied in polystyrene microsphere solutions, in chicken muscle (breast) and liver, and in porcine muscle and skin. The transition is discussed in terms of a diffusion process characterized by an angular diffusivity (radians(2)/mean free path) for the change in angular orientation of linearly polarized light per unit optical path traveled by the light.
  
  
  RESULTS
  Microsphere diffusivity increased from 0.031 to 0.800 for diameters decreasing from 6.04 microm to 0.306 microm, respectively. Tissue diffusivity varied from a very low value (0.0004) for chicken liver to an intermediate value (0.055) for chicken and porcine muscle to a very high value (0.78) for pig skin.
  
  
  CONCLUSIONS
  The results are consistent with the hypothesis that birefringent tissues randomize linearly polarized light more rapidly than nonbirefringent tissues. The results suggest that polarized light imaging of skin yields images based only on photons backscattered from the superficial epidermal and initial papillary dermis because the birefringent dermal collagen rapidly randomizes polarized light. This anatomic region of the skin is where cancer commonly arises.
authors.affiliation: Oregon Medical Laser Center, Providence St. Vincent Medical Center, Portland, Oregon 97225, USA. sjacques@ece.ogi.edu
authors.forename: S L
authors.initials: SL
authors.lastname: Jacques
authors.forename: J R
authors.initials: JR
authors.lastname: Roman
authors.forename: K
authors.initials: K
authors.lastname: Lee
mesh_terms: D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007834:Lasers / Q000706:statistics & numerical data*; D008027:Light; D008099:Liver; D008863:Microspheres; D018482:Muscle, Skeletal; D055095:Optics and Photonics; D010781:Photography / Q000295:instrumentation* / Q000379:methods*; D011137:Polystyrenes; D012867:Skin
chemical_list: D011137:Polystyrenes