Polarized light transmission through skin using video reflectometry: toward optical tomography of superficial tissue layers

Steven L. Jacques, Martin R. Ostermeyer, Lihong Wang, Dawn V. Stephens

Research output: Chapter in Book/Report/Conference proceedingConference contribution

46 Scopus citations

Abstract

The movement of polarized light through the superficial layers of the skin was visualized using a video camera with a polarizing filter. This study constitutes a description of the impulse response to a point source of incident collimated linearly polarized light. Polarization images reject unwanted diffusely backscattered light from deeper in the tissue and the specular reflectance from the air/tissue interface. Two experiments were conducted: (1) Video polarization reflectometry used a polarized HeNe laser (633 nm) pointing perpendicularly down onto a phantom medium (0.900-micrometer dia. polystyrene spheres in water). The video camera was oriented 10 degrees off the vertical axis and viewed the irradiation site where the laser beam met the phantom. Video images were acquired through a polarizing filter that was either parallel or perpendicular with the reference plane defined by the source, camera, and irradiation site on the phantom medium's surface. The source polarization was parallel to the reference plane. The two images (parallel and perpendicular) were used to calculate a polarization image which indicated the attenuation of polarization as a function of distance between the source and point of photon escape from the phantom. Results indicated a strong polarization pattern within approximately 0.35 cm (approximately 2.2 mfp') from source. [mfp' equals 1/(micron a plus micron s')]. (2) Optical fiber reflectometry using a polarized diode laser (792 nm) coupled to a polarization-maintaining single-mode fiber, and a multi-mode fiber collector to collect regardless of polarization. Reflectance as a function of fiber separation was measured for the source fiber oriented parallel and perpendicular with the reference plane. Results indicated that the strongest polarization propagated within approximately 0.43 cm (2.2 mfp') from source. The polarization survived approximately 2.2 mfp', which for skin at 630 - 800 nm (mfp' approximately equals 0.066 cm) corresponds to 1.5 mm (or 6.4 ps of travel at the speed of light). Using 6.4 ps as a maximum time of survival, classical paths of photon transport (Feynman paths) were calculated to illustrate the expected depth of interrogation by polarized imaging. The expected mean depth of photons is about 0.36 mm at these longer wavelengths. Shorter wavelengths would result in a shorter mfp' and therefore more superficial imaging of the skin. Polarization images offer an inexpensive approach toward 2-D acquisition of time- gated images based on the early light escaping the tissue. Polarization imaging is an opportunity for a new form of optical image especially useful for dermatology.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsR.Rox Anderson
Pages199-210
Number of pages12
StatePublished - Jan 1 1996
EventLasers in Surgery: Advanced Characterization, Therapeutics, and Systems VI - San Jose, CA, USA
Duration: Jan 27 1996Jan 30 1996

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume2671

Other

OtherLasers in Surgery: Advanced Characterization, Therapeutics, and Systems VI
CitySan Jose, CA, USA
Period1/27/961/30/96

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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  • Cite this

    Jacques, S. L., Ostermeyer, M. R., Wang, L., & Stephens, D. V. (1996). Polarized light transmission through skin using video reflectometry: toward optical tomography of superficial tissue layers. In R. R. Anderson (Ed.), Proceedings of SPIE - The International Society for Optical Engineering (pp. 199-210). (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 2671).