Co-localized line-field confocal optical coherence tomography and confocal Raman microspectroscopy for three-dimensional high-resolution morphological and molecular characterization of skin tissues ex vivo

Abstract

Line-field confocal optical coherence tomography (LC-OCT) is an optical modality that provides three-dimensional (3D) images of the skin at cellular resolution. Confocal Raman microspectroscopy (CRM) is a label-free optical technique that can provide point measurement of the molecular content of the skin. This work presents a method to co-localize LC-OCT and CRM acquisitions for morpho-molecular analysis of ex vivo skin tissues at cellular level. The co-localization method allows acquisition of Raman spectra at specific locations in a sample identified from a 3D LC-OCT image, with an accuracy of ± 20 µm. The method was applied to the characterization of tattooed skin biopsies with adverse tattoo reactions. LC-OCT images allowed to target specific regions in the biopsies where the presence of tattoo ink was revealed by detection of the Raman signature of ink pigments. Micrometer-sized foreign bodies of various materials as well as inflammatory cells were also identified within the biopsies. From these results, we demonstrate the value of the LC-OCT-CRM co-localization method and its potential for future ex vivo analysis of suspicious skin lesions.

Line-Field Confocal Optical Coherence Tomography (LC-OCT) for Skin Imaging in Dermatology

“…We believe that the relative lack of specificity of LC-OCT compared with histology could be compensated for, at least in part, by AI-based image analysis. On the other hand, the coupling of LC-OCT with spectroscopic techniques, such as Raman scattering spectroscopy, is another approach currently under development [55], enabling information on the molecular composition of tissues to be obtained in addition to purely morphological information, thus increasing the specificity of examinations.…”

Optical Methods for Non-Invasive Determination of Skin Penetration: Current Trends, Advances, Possibilities, Prospects, and Translation into In Vivo Human Studies

“…Thus, CRM in vivo provides the 1D z -stack point measurements (depth profiles), and the typical Raman spectra are shown in Figure 7 B. To precisely guide the Raman point measurements in vivo, the CRM could be combined with the RCLSM [ 220 ], OCT [ 221 ], or line-field confocal OCT [ 222 ] imaging modalities that rapidly visualize skin morphology at a subcellular resolution and allow the operator to assess a region of interest for Raman point measurements.…”

“…Thus, CRM in vivo provides the 1D z-stack point measurements (depth profiles), and the typical Raman spectra are shown in Figure 7B. To precisely guide the Raman point measurements in vivo, the CRM could be combined with the RCLSM [220], OCT [221], or line-field confocal OCT [222] imaging modalities that rapidly visualize skin morphology at a subcellular resolution and a The most important prerequisite for the determination of the penetration profile of the applied formulation (target substance) in the skin is the presence of differences between the Raman spectra of the untreated and formulation-treated skin, whose spectra always overlap completely or partially. Pre-processing routines for Raman spectra are always required prior to meaningful analyses, and include following procedures: wavenumber/intensity calibration prior to measurements; cosmic spike correction; spectra smoothing; noise reduction (e.g., using principal component analysis); and fluorescence background subtraction (mainly using higher-order polynomial and/or linear functions) [171,184,224,225].…”

High-speed, long-range and wide-field OCT for in vivo 3D imaging of the oral cavity achieved by a 600 kHz swept source laser

“…Since its inception, optical coherence tomography (OCT) has undergone remarkable progress, evolving from time-domain to spectral-domain configurations and, more recently, embracing the sophisticated swept-source OCT (SS-OCT) [ 1 – 3 ]. These continuous technological innovations have firmly established OCT as an indispensable tool in various biomedical imaging applications, spanning clinical fields such as ophthalmology [ 4 – 7 ], dentistry [ 8 – 12 ], dermatology [ 13 – 17 ], endoscopy [ 18 – 23 ], neuroscience [ 24 – 27 ], and more.…”