Spatially confined and temporally resolved refractive index and scattering evaluation in human skin performed with optical coherence tomography

Abstract

In the present applications of optical coherence tomography (OCT), parameters besides pure morphology are evaluated in skin tissue under in vivo conditions. Spatially mapped refractive indices and scattering coefficients may support tissue characterization for research and diagnostic purposes in cosmetics/pharmacy and medicine, respectively. The sample arm of our OCT setup has been arranged to permit refractive index evaluation with little mechanical adjustment of a lens within the objective. A simple algorithm has been derived. Known from atmospheric work, the Klett algorithm [J. D. Klett, "Stable analytical inversion solution for processing LIDAR returns," Appl. Opt. 20(2), 211-220 (1981)] has been applied to the same data set for retrieval of scattering coefficients. Both parameters have been measured in layered structures in skin like stratum corneum, epidermis and dermis. Significant water content in a localized sweat gland duct has been observed by refractive index evaluation. Time studies over 1.5 h permitted a first understanding about physiological changes in skin which are not obtainable by intrusive methods.

Monitoring Blood Glucose Changes in Cutaneous Tissue by Temperature-modulated Localized Reflectance Measurements

“…Cutaneous red blood cell flux varies between comparable sites in the same individual, and 1-mm 2 areas of vascular "territories" surrounded in part by relatively avascular areas have been identified in human skin (35)(36)(37). An optical coherence tomography study of human skin showed pockets of different refractive index values in the skin (38 ). Thus, even if the shape of the MTT curve is tracking the change in glucose concentration, a constant-term difference may result from positioning of the illumination and detection fibers with respect to vascular territories and avascular areas in the skin, and/or with respect to pockets with different refractive index values.…”

Optical coherence tomography—current technology and applications in clinical and biomedical research

“…Knüttel et al expanded Tearney's focus tracking method to measure depth-resolved changes of the refractive index [131]. Based on the model by Thrane et al relating the OCT signal strength to scattering [132], Letvitz et al extracted the scattering coefficient and the effective anisotropy factor from OCT A-scans [133], and Turchin et al developed an algorithm to derive the scattering coefficients of multi-layer samples [134].…”

Average refractive index of tendon as a function of water content

“…One of the optical parameters that can be directly measured for biological tissues is the average refractive index of the tissue [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. In the literature, one can find estimates of the average refractive index for many types of tissues (cornea, sclera, dermis, epidermis, brain tissue etc.…”