Contrast improvement in scattered light confocal imaging of skin birefringent structures by depolarization detection

Abstract

Journal of BIOPHOTONICSHere we describe a method for enhancing the contrast in imaging skin birefringent structures. The method relies on polarization-dependent optical properties and is implemented using cross polarized confocal microscopy. The experimental data obtained using ex-vivo and invivo measurements on human scalp hairs and human skin demonstrate a significant dependence of the change in polarization of light that interacted with the birefringent hair on the orientation of the incident polarization. The polarization dependent contrast, defined as the ratio of intensity measured for different orientations of the incident polarization when observed using cross polarized confocal microscopy furthermore depends on the hair type/degree of pigmentation and on the focusing depth inside the hair. No such dependence was observed for the upper skin layers, including the stratum corneum and epidermis. We propose a new method for enhancing the contrast between the skin and the birefringent hair by the use of cross polarized confocal microscopy combined with the variation of the polarization of the incoming light. Potential applications of this method include imaging of hairs for assessing the efficacy of hair removal methods and measurement of skin birefringence. The underestimation of the birefringence content resulting from the orientation related effects associated with the use of linearly polarized light for imaging tissues containing wavy birefringent structures could be minimized by this method.CPCLSM images obtained in-vivo with the direction of incident polarization at different angles to the orientation of the hair axis.

Qualitative investigation of fresh human scalp hair with full-field optical coherence tomography

“…Cross-polarized CLSM (CP-CLSM), a variant of the confocal imaging regime, has provided contrast-enhanced hair imaging using polarization dependence of birefringent hair structures without aid of any chemical labeling. 13,14 However, use of the technique is rather specialized in fully keratinized hair structures like cortex. Multiphoton microscopy such as two-photon excitation microscopy (TPEM) or second harmonic generation microscopy (SHM) has been employed for internal investigation of the hair.…”

Ex Vivo Assessment of Carbon Tetrachloride (CCl4)-Induced Chronic Injury Using Polarized Light Spectroscopy

“…27 More recently, experiments have done on human scalp hairs and human skin with polarized light, which improved the contrast in confocal imaging of skin by using the depolarization of light. 28 Mueller matrix polarimetry has also been successfully used for assessment of the myocardium, including normal, infarcted, and stem cell-regenerated tissues, in which tissue anisotropy was exploited as a distinguishing criterion. 29…”

Quantitative Assessment of Birefringent Skin Structures in Scattered Light Confocal Imaging Using Radially Polarized Light

“…Recently, we have shown that cross-polarized confocal laser scanning microscopy, when combined with variation of the polarization of the incoming light, can be used to enhance the contrast between the birefringent hair cortex and the non-birefringent skin [14,15]. In this manuscript, we for the first time report on the orientation related effects of linearly, circularly and radially polarized light on the change in polarization of backscattered light from birefringent structures using ex vivo measurements on human scalp hairs and in vivo measurements on hair and skin in a cross polarized confocal microscope.…”