Imaging skin pathology with polarized light

[+] Author Affiliations
Steven L. Jacques, Jessica C. Ramella-Roman, Ken Lee

Oregon Health and Science University, Departments of Dermatology, Electrical and Computer Engineering, Portland, Oregon

and Providence St. Vincent Medical Center, Oregon Medical Laser Center, Portland, Oregon

J. Biomed. Opt. 7(3), 329-340 (Jul 01, 2002). doi:10.1117/1.1484498
History: Received Mar. 18, 2002; Revised Apr. 2, 2002; Accepted Apr. 4, 2002; Online August 01, 2002
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Linearly polarized light that illuminates skin is backscattered by superficial layers and rapidly depolarized by birefringent collagen fibers. It is possible to distinguish such superficially backscattered light from the total diffusely reflected light that is dominated by light penetrating deeply into the dermis. The method involves acquisition of two images through an analyzing linear polarizer in front of the camera, one image (Ipar) acquired with the analyzer oriented parallel to the polarization of illumination and one image (Iper) acquired with the analyzer oriented perpendicular to the illumination. An image based on the polarization ratio, Pol=(IparIper)/(Ipar+Iper), is created. This paper compares normal light images, represented by Iper, and Pol images of various skin pathologies in a pilot clinical study using incoherent visible-spectrum light. Images include pigmented skin sites (freckle, tattoo, pigmented nevi) and unpigmented skin sites [nonpigmented intradermal nevus, neurofibroma, actinic keratosis, malignant basal cell carcinoma, squamous cell carcinoma, vascular abnormality (venous lake), burn scar]. Images of a shadow cast from a razor blade onto a forearm skin site illustrate the behavior of Pol values near the shadow edge. Near the shadow edge, Pol approximately doubles in value because no Iper photons are superficially scattered into the shadow-edge pixels by the shadow region while Ipar photons are directly backscattered from the superficial layer of these pixels. This result suggests that the point spread function in skin for cross-talk between Pol pixels has a half-width-half-max of about 390 μm. © 2002 Society of Photo-Optical Instrumentation Engineers.

© 2002 Society of Photo-Optical Instrumentation Engineers


Steven L. Jacques ; Jessica C. Ramella-Roman and Ken Lee
"Imaging skin pathology with polarized light", J. Biomed. Opt. 7(3), 329-340 (Jul 01, 2002). ; http://dx.doi.org/10.1117/1.1484498

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