The COVID-19 pandemic increased interest in large-scale disinfection of public spaces using UV-C germicidal lights. However, excessive UV-C exposure harms the skin and cornea. Although novel Far UV-C (180 – 230 nm) sources are widely considered safe, an easy and non-invasive experimental assessment of UV damage could help to exclude any health risks of extensive Far UV-C exposure.
Dynamic-microscopic optical coherence tomography (dmOCT) is a non-invasive, label-free technique providing sub-cellular resolution images. This study used dmOCT to confirm Far UV-C's skin safety with in-vitro models. Results showed no signs of keratinocyte damage, while UV-B exposed samples express immediate structural and functional changes.
This project proposes an alternate method to DIN/ISO parameters for analyzing the effects of intrinsic and extrinsic aging on skin morphology. This method improves the efficacy of assessing aging by evaluating the surface and subsurface of the skin. The volumetric data obtained using OCT was processed using a machine learning approach to obtain DEJ segmentation, which was further segmented to obtain the morphological information of the micro-plateaus. The results showed that the flattening of DEJ due to aging is accompanied by changes in the size and shape of micro-plateaus in the DEJ.
KEYWORDS: Optical coherence tomography, Skin, In vitro testing, Temperature metrology, Mode conditioning cables, Signal processing, Scattering, Acquisition tracking and pointing, 3D modeling, Motion models
Microscopic optical coherence tomography (OCT) provides three-dimensional, high-resolution imaging but lacks (sub-) cellular contrast. Dynamic-microscopic OCT (dmOCT) is an approach exploiting dynamic changes of the scattering behavior in metabolically active cells. However, the underlying cellular processes responsible for those intensity fluctuations and hence the dynamic signals are not finally identified yet. Here, we present the effects of different temperatures and metabolic reagents on dmOCT images of an in-vitro human skin model. Our data indicates a dependency of the dmOCT signals on metabolic activity rather than Brownian motion and suggests dependency on the metabolic state.
Intrinsic and extrinsic aging of human skin induces significant morphological changes to its surface. The most prominent and important feature in cosmetics and dermatology is the alteration of the wrinkles. Roughness parameters (Ra, Rmax) described by DIN/ISO disregard the skin’s micro-structure. Hence, we introduce an alternative method of skin roughness evaluation by analyzing the size and shape of micro-structures using optical coherence tomography. Measurements of young and elderly subjects were acquired. The skin of elderly subjects showed a decrease in micro-structures compared to the skin of young subjects which was predominated by triangular shapes, whereas rhomboids prevail among the elderly.
Computational adaptive optics (CAO) is emerging as an attractive alternative to hardware-based solutions for diffraction-limited optical coherence tomography, e.g., of the human retina. Still, to become a reliable and robust solution, many challenges need to be solved. Here, we present CAO based on multiple randomized sub-apertures in combination with suitable filtering to remove disturbing artifacts. We show that this approach can reliably detect aberrations, and we compare results to other algorithms, such as optimization of imaging quality. We also demonstrate that the filtering of reflecting image structures is essential for a robust determination of aberrations.
We demonstrate functional in vivo imaging of photoreceptor and neuronal layers within the living human retina by looking at the expansion of their optical path length. To this end, we use a special full-field swept-source optical coherence tomography system that acquires all lateral points in parallel, achieving a high-speed data acquisition with up to 200 volumes per second. A combination of computational motion and aberration correction with a suitable phase evaluation scheme yields minuscule changes after exposing the photoreceptors to a white light stimulus.
Non-invasive functional retinal imaging in humans is of tremendous interest. By using phase-sensitive full-field swept-source OCT (FF-SS-OCT) we demonstrated simultaneous quantitative imaging of the optical activation in the photoreceptor and ganglion/inner plexiform layer. Since the signals from the ganglion cells layer are ten-fold smaller than those from the photoreceptor cells a new algorithms for suppression of motion artifacts and pulsatile blood flow in the retinal vessels is important. With improved data evaluation we simultaneously measured the activation of photoreceptors and ganglion/inner plexiform with high quality and were able to analyze the spatial and temporal response of cells in the ganglion/inner plexiform over more than 10 seconds.
Using phase-sensitive full-field swept-source optical coherence tomography we already showed that morphological changes in the photoreceptor outer segments are detectable. Those signals manifest themselves in an elongation of the optical path length. Using improved post.processing we report on progress in detecting signals in the neuronal layers of the human retina. The spatially resolved signals show a characteristic time course and by combining these with simultaneous measurements of the photoreceptors we were able to generate a wiring map of the neuronal retina.
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