This PDF file contains the front matter associated with SPIE Proceedings Volume 11934, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Objective: to study the dynamics of the state of autografts of skin and allodermal protectors on a wound using multimodal optical monitoring. Material and methods. A burn wound was simulated in rats (n = 16), 20% of the wound area was covered with skin autografts. The allodermal protector of 0.35 mm thick was applied over the autografts. Studied in vivo the state of the grafts for 10 days: saturation - according to diffuse optical spectroscopy (DOS); perfusion - according to laser Doppler flowmetry (LDF); microstructure - according to optical coherence tomography (OCT). Results. Multimodal monitoring of blood circulation, metabolism and microstructure of skin grafts on a burn wound showed that changes in auto- and allografts occur asynchronously. In the tissues of the autograft, blood saturation directly correlated with the restoration of perfusion (Spearman's coefficient = 0.795); in the allograft, the correlation between perfusion and saturation was weakly inverse (-0.179). Those differences were confirmed by OCT data and histological analysis: allografts lost their normal microstructure simultaneously with a rapid decrease of the blood saturation, despite the preservation of perfusion parameters.

Line-field confocal optical coherence tomography (LC-OCT) is an optical technique generating three-dimensional (3D) images of the skin at cellular resolution. Confocal Raman microspectroscopy (CRM) is an optical modality that provides a point-wise molecular fingerprint of samples. We have developed a method to co-localize data acquired by separate LC-OCT and CRM systems. LC-OCT allows for recording 3D morphological overview images in which points of interest (POIs) can be localized for molecular analysis using CRM. A biopsy of skin with a red-colored tattoo with unknown ink composition was analyzed using co-localized LC-OCT and CRM. After acquisition of a 3D LC-OCT image, specific POIs were targeted inside the biopsy, based on their morphological features: POIs located in the epidermis where no ink was expected to be found as well as POIs located in bright areas of the dermis, down to 275 μm in depth, likely indicating the presence of tattoo ink. Analysis of the spectra at these specific POIs confirmed the absence of tattoo ink in the epidermis and its presence in the bright areas in the dermis. A stronger molecular signal of ink in the brightest areas of the dermis identified with LC-OCT was also revealed, suggesting a higher amount of ink. The combination and co-localization of LC-OCT and CRM brings a new level of characterization of the skin, enabling molecular analysis of POIs based on their morphological aspect at cellular-resolution within a volume, which could be of great interest in dermatology and dermo-cosmetics.

Optical clearing is a method to overcome the limitation of optical imaging depth especially for clinical in vivo microscopies of dermatology. According to previous studies, glycerol could effectively increase the signal intensity deep inside dermis. Other optical clearing agents (OCAs), like propylene glycol (PG) and polyethylene glycol (PEG) 400, were reported to cause better optical clearing effects. However the experiment conditions of different OCAs varied, including the penetration enhancers, application time, selection of samples and areas, and microscopy technologies. These inconsistent conditions lead to inconclusive results. Moreover, it is difficult to study this effect on human skin in vivo due to the different conditions of skin pH value, temperature, moisture, and microbiology. In this study, we aim to compare the efficacy among varies OCAs that improve the image quality deep inside the dermis for in vivo human skin imaging. Harmonic generation microscopy was used for in vivo imaging which could provide high resolution and distinguish epidermis from dermis. Several OCAs (25% PG, 40% PG, 25% PEG 400, 50% PG, 50% PEG 400, 50% glycerol, water) with or without ultrasound treatment were included. Among these treatments, 25% PG with 5 minutes of ultrasound treatment for total 60 minutes of application times was found to be with the best efficacy, judged by the in vivo maximum second harmonic generation signals from collagen fibers in dermis. This finding will not only be helpful for the optical clearing research but would also benefit the in vivo human skin imaging techniques in the future.

Some tumor resection procedures, such as Mohs surgery, utilize intraoperative histology for tumor margin assessments. Gold standard rapid histology methods are time-consuming for patients under anesthetic and rapid freezing techniques are prone to artifacts. The recent development of microscopy with ultraviolet surface excitation (MUSE) introduces a new possibility for the rapid imaging of the cut tissue surface using fluorescent dyes. The high attenuation of ultraviolet light limits MUSE signals to thicknesses close to typical histology sections. To generate MUSE images with familiar H&E-like contrast, recent work has explored the transformation of MUSE images to “virtual” H&E-like images using unsupervised deep learning models trained on unpaired images of separate tissues treated with each stain. Here, we present a method for acquiring registered images of the same tissue with MUSE and real H&E imaging using sequential staining and dye removal. Tissue blocks are flash frozen and sectioned for mounting onto slides and staining with MUSE fluorescent dyes. After MUSE imaging, a sequential immersion of the slides in increasing concentrations of ethyl alcohol followed by rehydration, similar to steps in paraffin-based histology processing, is sufficient to remove all fluorescent dyes. Rinsed tissue slides are then subjected to traditional H&E staining and brightfield imaging. Data of registered image fields of skin and pancreas are presented along with initial machine learning-based transformations from MUSE to H&E contrast. This protocol will be useful to obtain paired images for training, testing, and quantitative validation of virtual H&E reconstructions from MUSE images.

Enhanced Thermal Imaging (ETI) is a new thermal infrared (8-10 μm) imaging technique that delineates blood vessels embedded in water-rich tissue in real time. ETI uses selective heating of blood via illumination with a green (532 nm) LED to produce a thermal contrast (∼ 0.5°C) between blood vessels and surrounding water-rich tissue. The warmer blood vessels appear brighter in the thermal image. In a previous study, the growth of breast cancer tumors in an 4T1 murine orthotopic model was successfully monitored in vivo using ETI. The images highlighted regions that are routinely targeted for surgical excision around solid mass tumors. Recently, improvements to the acquisition software have enabled real-time imaging with this technique, highlighting ETI’s potential use as an intraoperative imaging tool. In this study, simulations of direct illumination and heating of the blood vessels embedded in tissue were conducted to understand the effects of LED power and vessel depth on the ability of ETI to detect vascular structures. The simulations were performed with an open-source MATLAB integrated solver, MCmatlab.

Reoperations and unnecessary removal of healthy tissue could be reduced if non-invasive imaging techniques were available for presurgical tumor delineation in skin cancer. In this study, 3D multiwavelength photoacoustic imaging was performed ex vivo on 25 melanomas and 27 nevi. The tumors were delineated using spectral unmixing at 59 excitation wavelengths, from 680 nm to 970 nm, accounting for multiple tissue chromophores. The tumor dimensions determined with photoacoustic imaging were strongly correlated with those determined by histopathological examination for both melanomas and nevi.

Melanoma is the most aggressive type of skin cancer with an estimated 106,110 new cases in the US in 2021. The 5-year survival rate of patients with early-stage melanoma is ~99%; however, ~13% of melanoma patients are diagnosed with lesions already at intermediate or advance stages, associated with a 5-year survival rate of ~66% and ~27% respectively. The current diagnosis technique involving visual inspection and biopsy often fail to visually distinguish clinically similar lesions; in particular, melanoma can be mistaken for benign lesion pigmented seborrheic keratosis (pSK). In this work, a deep learning model using Long Short-Term Memory (LSTM) networks is trained on the multispectral autofluorescence lifetime dermoscopy images collected from 41 benign lesions including solar lentigo and pSK, and 19 malignant lesions including melanoma, superficial basal cell carcinoma (BCC) and nodular BCC. The model is trained on the image pixels containing concatenated fluorescent decay signals from three emission channels. The posterior probabilities predicted for each pixel location, is used to construct probability maps of the images. Receiver Operator Characteristics (ROC) constructed on the threshold of the median value of the posterior probability map determines the effectiveness in distinguishing benign and malignant lesions. The entire dataset is split into training, validation, and test sets. The hyperparameters are tuned using the validation set while the model performance is estimated using the test set. The mean and standard deviation of the Areas Under the Curve (AUC) of the ROCs generated with 10 random test sets is 0.82 ± 0.04.

Line-field confocal optical coherence tomography (LC-OCT) is an imaging technique based on a combination of reflectance confocal microscopy and optical coherence tomography, allowing three-dimensional (3D) imaging of skin in vivo with an isotropic spatial resolution of about 1.3 micron and up to 400 microns in depth. Cellular-resolution 3D images obtained with LC-OCT offer a considerable amount of information for description and quantification of the upper layers of in vivo skin using morphological metrics, which can be critical for better understanding the skin changes leading to aging or some pathologies. This study introduces metrics for the quantification of the epidermis, and uses them to describe the variability of healthy epidermis between different body sites. These metrics include the stratum corneum thickness, the undulation of the dermal-epidermal junction (DEJ), and the quantification of the keratinocyte network. In order to generate relevant metrics over entire 3D images, an artificial intelligence approach was applied to automate the calculation of the metrics. We were able to quantify the epidermis of eight volunteers on seven body areas on the head, the upper limbs and the trunk. Epidermal thicknesses and DEJ undulation variations were observed between different body sites. The cheek presented the thinnest stratum corneum the least undulated DEJ, while the back of the hand presented the thickest stratum corneum and the back the most undulated DEJ. The process of keratinocyte maturation was evidenced in vivo. These 3D in vivo quantifications open the door in clinical practice to diagnose and monitor pathologies for which the epidermis is impaired.

We assessed the reliability of handheld laser speckle contrast perfusion imaging by evaluating mounted/handheld measurement pairs operated on psoriasis lesions in three steps. First, we made a denoised perfusion map per measurement based on spatial alignment of raw speckle frames and temporal averaging of perfusion frames. Second, we used the measured on-surface speed information to compensate the movement-induced perfusion by extrapolation of the local perfusion values to the value corresponds to zero on-surface speed. Third, we compared mounted/handheld measurement pairs based on perfusion inhomogeneity and increased perilesional perfusion criteria independent of the movement artefact compensation mentioned in the second step. We conclude that after proper post-processing, handheld LSCI measurements can be as reliable as mounted measurements in terms of geometrical distorting, but with challenges to be overcome for correcting perfusion values.

Total-body photography (TBP) has gained increasing attention for facilitating early melanoma detection. TBP has advantages of monitoring temporal changes in lesions, screening a large number of lesions efficiently, and providing anatomical locations for dermatoscopic images. Since various digital imaging systems for TBP have been proposed, there is a need for a unified format for the storage of the data from TBP. Digital Imaging and Communications in Medicine (DICOM) is the international standard for medical imaging. Thanks to a considerable effort to develop dermatology-specific extensions to the DICOM standard, there is a recent supplement to the DICOM standard for individual dermoscopic images. This supplement, however, does not cover the requirements for TBP, which may include multiple wide field-of-view images. Moreover, TBP may be obtained using various methods i.e. the images can be acquired with either consumer-grade cameras, smartphones, or an automatic scanning machine. This paper provides an overview of the specific requirements and an outline of a “Work Item” leading to a Total Body Photography Information Object Definition (IOD). The “Work Item” is inclusively designed for accommodating current variants of TBP data to be compatible with the DICOM standard for dermoscopy and applicable to future systems and other potential use of TBP. We verified the feasibility of the proposed TBP DICOM in an imaging-rich full-body scanning system.

In this study, we compared the photothermal effects induced by the pulsed lasers including a fractional CO2 laser (=10600 nm) and a nanosecond Nd:YAG laser (=1064 nm). To investigate the induced photothermal effect, a spectral-domain optical coherence tomography (SD-OCT) system with a central wavelength of 840 nm was used to acquire 3D images of skin before and after the laser treatment. From the OCT results, the microscopic ablation zone (MAZ) resulted from the fractional CO2 laser can be identified that caused a stripe-shape photodamage on skin, ranging from the epidermis layer to the dermis layer. In contrast, the intra-dermal laser-induced optical breakdown (LIOB) induced by the nanosecond pulsed laser can also be observed from the OCT results.

OCT is a promising imaging modality for the field of dermatology, but lack of research is hinders its use in everyday practice. Our study provides qualitative and quantitative analysis of healthy skin from various anatomic locations. Qualitative analysis showed identification of key structures including epidermis, dermis, and dermal epidermal junction (DEJ), as well as accessory structures. Quantitative analysis produced a characteristic absorption spectra of healthy skin, with a peaked intensity at stratum corneum, second peak at DEJ, and variations due to accessory structures. This analysis is valuable for OCTs use as a diagnostic aid in determining healthy vs pathologic skin.

Multiphoton microscopy (MPM) has been discovered for several decades now. With noninvasive nature, subcellular resolution, relatively high imaging depth, distinctive biochemical-based imaging contrast, and the ability to be combined with other imaging and spectroscopic modes, MPM has been applied in many different fields in characterizing biological tissues and organisms, including medical diagnosis and treatment, drug development and penetration, cosmetic research, etc. In particular, its application in cosmetic industry has been advancing exponentially. This review will be focusing on a brief historical review and some recent advancements of MPM with a focus on its applications in cosmetic research. With the developments in both the hardware and software, such as the recent improvements in tunable laser sources, scanning speed and angles, the speed of computing, real-time image processing, etc., MPM will continue to grow dramatically. Together with other imaging and spectroscopic modalities, it is envisioned that higher imaging resolution, larger image field, faster image acquisition and processing, as well as more complementary information will be achieved, and will help revolutionize the field of cosmetic research.

Survival from melanoma, the deadliest form of skin cancer, depends heavily on early detection. Several non-invasive medical imaging modalities have been developed to detect melanoma, of which optical coherence tomography (OCT) is gaining popularity. Although OCT generally does not yet provide sufficient performance in detecting melanoma, radiomic studies involving quantitative OCT image analysis demonstrate promising results. We propose extracting a large set of radiomic features from OCT images of skin, exploring how the features differ between melanoma and non-melanoma, and performing feature selection to identify the most informative OCT radiomic features that characterize melanoma for improved melanoma detection.

Optical coherence tomography (OCT) images enable the visualization of cell layers, and accurate layer thickness is crucial for disease diagnosis and treatment tracking. To measure layer thickness, delineating the layer boundaries is the first step. In this paper, we proposed a time-efficient layer segmentation method developed on central unit processors (CPUs). This method consists of convolutional neural networks (CNN) and graph search (CNN-GS). CNN-GS aims to automatically segment two defined boundaries to calculate the epidermal thickness. We applied our method to 110 skin OCT images from various body locations, taken from 13 healthy individuals aged between 20 and 60 years, to evaluate the performance and versatility of our method. Our method demonstrated an overall 94.68% accuracy on patch-wise classification and an 85.81% accuracy on segmentation position accuracy as compared to manual segmentation, allowing 94.87% accuracy on epidermal thickness. In addition, our method performed a near real-time image analysis, costing less than 1 second per skin OCT image to delineate the layer boundaries.

Optical coherence tomography is a three-dimensional imaging modality that captures microstructures of the tissue. The application of OCT in dermatology is limited due to the low visibility in these images. Numerous image denoising and enhancement algorithms have been implemented for quality improvement of the OCT skin images. One way to evaluate the performance of these algorithms is to quantify the quality of the processed images using different image quality metrices. Current image quality metrics though do not fairly represent the visual quality of the images. We propose an algorithm to quantify the quality of OCT images compatible with human visual perception, and the diagnostically important features in skin images. We implement a new metric called Signal to Noise Ratio. The metric is assessed on different number of averaged OCT images taken from the same cross section of the skin.

Line-field confocal optical coherence tomography (LC-OCT) is an optical technique based on a combination of reflectance confocal microscopy and optical coherence tomography to generate cellular-resolution images, in either vertical (x×z) or horizontal (x×y) sections, or in three-dimensions (3D), with a field of view of 1.2×0.5×0.4 mm³ (x×y×z). LC-OCT was originally designed for in vivo skin imaging. Here, we present a novel implementation of LC-OCT that enables ex vivo biological tissue imaging with an extended field of view. In this implementation, a specific sample holder is used so that the head of the LC-OCT device is not in contact with the sample to be imaged. The sample can thus be displaced independently of the LC-OCT head in a controlled manner using multi-axes motorized translations, while acquiring LCOCT images. A stitching algorithm is used to extend the field of view of vertical section images, horizontal section images, and also 3D images. In addition, as the device can also acquires color images of the sample surface (dermoscopic images) in parallel with the tomographic LC-OCT images, a similar mosaicking approach can be applied to the surface images. The method allows the reconstruction of a wide-field surface image of the sample, precisely collocated to the LC-OCT mosaic. This approach allows full characterization of entire skin punch biopsies of several millimeters with ~ 1 micron resolution, in 3D, and over a depth of 0.4 mm, with an associated dermoscopy-like image of the entire tissue surface.

Tattooing and permanent makeup are very popular [1]. Nowadays there is practically no information about the effect of artificial pigment on the surrounding tissues. The issue of removing artificial pigment, the selection of individual parameters of laser radiation, depending on the level of occurrence of the pigment and individual characteristics of the skin, and control of the effectiveness of the procedure is also no less urgent. Optical coherence tomography (OCT) is a promising method for noninvasive examination of the skin, which allows one to assess its structure and morphological changes occurring in it in real time [2,3]. The purpose of this work is to assess the condition of the skin containing artificial pigment before and after laser tattoo removal using the method of optical coherence tomography (OCT).

In order to understand pathogenic mechanism of allergic dermatitis, it is important to find morphological changes of the internal structure of the skin by non-invasive imaging. Optical coherence tomography (OCT) is powerful tool for in vivo tomographic imaging of the internal microstructure in biological tissue. We propose in vivo observation of allergic skin of guinea pigs by OCT. As a result, epidermis thickening became evident as the days passing since Day 7, and the capillary vessel expansion was confirmed since Day 14; the process of inflammation development was successfully observed.

Skin mimicking optical tissue phantoms are widely used in diagnostics systems for characterization, optimization, routine calibration and validation. In general, solid phantoms are more preferred in comparison to liquid phantoms. Therefore, our aim is to prepare and characterize the solid tissue phantoms having skin equivalent optical properties. In this work, we have used epoxy resin and hardener as a base material and titanium oxide (TiO₂) nanoparticles and ink as a scatterer and absorber media, respectively. The total transmission (Tt), collimated transmission (Tc), and diffuse reflectance (Rd) spectra of the developed phantoms were measured with an integrating sphere installed in UV-VIS spectrometer within the wavelength range 400-700 nm. To characterize the optical properties such as absorption (μa), reduced scattering (μs’), and anisotropy factor (g) of the developed tissue phantoms, the numerical model based on Inverse Adding Doubling (IAD) has been used. With various concentrations of absorber and scatterer, a calibration curve was prepared. The calculated experimental optical properties from IAD matched with the predicted intrinsic optical properties of the skin. Thus, the preliminary results suggest that the recipe used in this study may be used as an alternative approach to developing skin mimicking solid optical phantom for diagnostics system applications.

Many skin and systemic diseases are accompanied by changes in the vessels of the skin. The role of the vascular component in the pathogenesis of diseases in most cases remains underestimated and is not sufficiently taken into account in the treatment. One of the reasons is the lack of safe, effective and accessible methods of objective assessment of skin vessels. The possibilities of the histological method are limited [1] due to vascular damage during biopsy and manufacture of the drug, as well as the inability to perform multi-focal and dynamic studies. Capillaroscopy and dermatoscopy also do not solve the problem, as they allow only indirectly to judge the condition of the skin vessels [2]. The possibilities of other non-invasive methods of examining skin vessels are being studied. One of the promising methods of lifetime examination of skin vessels is optical coherence tomography (OCT). This is a high-resolution (10-20 mk) method for visualizing the structure of biological tissues, using low-intensity near-infrared light as probing radiation [3]. The purpose of the work To study the possibilities of using OCT and 3D OCT to assess the state of the microcirculatory bed of the skin.