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

Jacques, Steven L. and Ostermeyer, Martin and Wang, Lihong and Stephens, Dawn (1996) Polarized light transmission through skin using video reflectometry: toward optical tomography of superficial tissue layers. In: Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VI. Proceedings of SPIE. No.2671. Society of Photo-optical Instrumentation Engineers (SPIE) , Bellingham, WA, pp. 199-210. ISBN 9780819420459.

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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-µm dia. polystyrene spheres in water). The video camera was oriented 10° 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' = 1/(µ_a + µ_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 ~2.2 mfp', which for skin at 630 - 800 nm (mfp' ≈ 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.

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Wang, Lihong0000-0001-9783-4383
Additional Information:© 1996 Society of Photo-Optical Instrumentation Engineers (SPIE). This work was supported by the NIH (R29-HL45045) and the Dept. of Energy (DE-FG03-95ER61971).
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-95ER61971
Series Name:Proceedings of SPIE
Issue or Number:2671
Record Number:CaltechAUTHORS:20181207-161549065
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Official Citation:Steven L. Jacques, Martin R. Ostermeyer, Lihong V. Wang, Dawn V. Stephens, "Polarized light transmission through skin using video reflectometry: toward optical tomography of superficial tissue layers," Proc. SPIE 2671, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VI, (17 May 1996); doi: 10.1117/12.240009
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91616
Deposited By: George Porter
Deposited On:11 Dec 2018 20:49
Last Modified:16 Nov 2021 03:42

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