Widefield spatial frequency domain imaging of tissue oxygen saturation (StO2), superficial (HbT1) and deep (HbT2) hemoglobin concentrations was performed on an arterial-venous insufficiency created by a forearm vascular occlusion test in 15 healthy subjects. Measured StO2 and HbT2 were significantly higher for regions of interest having underlying vessels compared to those without (microvasclature) at each time point (p < 0.01). During occlusion, the decrease in StO2 was greater for microvascular regions. These spatially resolved measurements suggest that image-based analysis is important as probe measurements can be confounded by probe location on the heterogeneous tissue.

The extend of skin fibrosis in scleroderma patients is currently assessed using the semi-quantitative modified Rodnan skin score (mRSS) which is an assessment of skin thickness. We investigated the use of spatial frequency domain imaging (SFDI) for more quantitative and reliable assessment of skin fibrosis. SFDI measurements were conducted at 6 body locations of 10 control subjects and 10 patients with scleroderma. SFDI results, especially reduced scattering coefficient, show strong correlation with the mRSS score measured by the physician at the same body locations suggesting that SFDI is a reliable tool to quantify skin fibrosis in scleroderma patients.

We aimed to integrate a series of novel optical techniques, termed coherent spatial imaging (CSI), into the same footprint as current pulse oximeters that provides absolute measurements of blood flow, oxygenation, oxy- and deoxy-hemoglobin concentrations, tissue scattering, and tissue absorption. We developed a first-generation, multi-wavelength CSI prototype for comparisons to diffuse optical spectroscopy and diffuse correlation spectroscopy (DOS/DCS). We measured silicone-base tissue phantoms and performed arterial occlusions to validate the CSI device. The CSI prototype results agreed with the DOS/DCS results. This is an important first step towards enhancing prolonged care through the development of a low-cost, multi-wavelength CSI device.

Multi-contrast jones matrix optical coherence tomography (JM-OCT) is demonstrated. JM-OCT provides not only the standard three-dimensional OCT but also the tomographies of attenuation coefficient (AC), birefringence, degree-of-polarization uniformity (DOPU), and OCT angiography. This talk briefly review the principle of JM-OCT, and then examples of in vivo skin imaging are shown. It is shown that the deep dermis has high birefringence, while the epidermis has low birefringence. A study about the relationship between the optical properties and the wrinkle morphology is also presented. It shows that the birefringence and DOPU at around 170-µm depth and the AC at around 250-µm depth significantly relate with the wrinkle morphology.

Summary: We developed a fully automated microregistration method that enables repeated in vivo skin microscopy imaging of the same tissue microlocation and specific cells over a long period of days and weeks with unprecedented precision. Applying this method in conjunction with in vivo multimodality multiphoton microscope, the behavior of human skin cells such as cell proliferation, melanin upward migration, blood flow dynamics, and epidermal thickness adaptation can be recorded over time, facilitating quantitative cellular dynamics analysis.

Polarization-resolved second-harmonic-generation (PR-SHG) microscopy simultaneously visualizes the orientation angle and degree of crystallinity in collagen fibers in tissues. In this paper, we developed fast PR-SHG microscopy based on pixel-by-pixel rapid polarization switching applicable for in situ measurements of the human skin. The demonstrated results indicated that our system would be a powerful tool for optical assessment of dermal collagen fiber in cosmetics research.

We present a handheld deep-tissue imaging device based on dual-axis optical coherence tomography (DA-OCT) at 1.3 μm wavelengths. We validate our approach for skin and dental imaging using various imaging phantoms and preliminary human results. We present a quantitative discussion of the necessary engineering improvements required to minimize the distal scanning optics required for DA-OCT, along with a quantitative review of system performance.

Cutaneous metastases are relatively rare and often require an invasive biopsy for diagnosis. A novel, non-invasive RCM-OCT device combines the advantage of reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) by providing RCM high-resolution images in the horizontal plane and OCT low-resolution images in the transverse plane. We describe RCM and OCT characteristics of cutaneous metastases using this device to elucidate its utility for diagnosis and management. Seven patients with clinically suspicious cutaneous metastases from breast cancer were imaged using the RCM-OCT device. We found that the RCM-OCT device can detect cutaneous metastases and aid in non-invasive diagnosis.

We perform micron-level co-registration of two-photon fluorescence microscopy (TPFM) images with en face frozen section analysis (FSA) histology. We demonstrate that TPFM has excellent sensitivity and specificity for evaluating squamous cell carcinoma (SCC) on surgical margins.

Mohs Micrographic Surgery (MMS) needs optical biopsy methods for tumor margin determination. Although confocal microscopy CM) has been used, CM has poor contrast to detect cancer cells with reflection contrast. We developed combined reflectance confocal (RC) & Moxifloxacin based two-photon (MB-TP) microscopy for high contrast. Here, combined microscopy was tested in various skin cancer tissues. Combined microscopy visualized both cell & extracellular matrix. Basal cell carcinoma nests were detected and distinguished from glands. Squamous cell carcinoma was detected with some features. This study showed combined microscopy has potentials for guiding MMS.

A Photoacoustic Remote Sensing (PARS) microscopy system is presented for label-free histological imaging of skin tissues. PARS captures label-free optical absorption contrast visualizing cell nuclei, connective tissues, lipids, and other structures with contrast analogous to common histochemical stains. Imaging is demonstrated in unprocessed human skin with basal cell carcinoma, squamous cell carcinoma, and melanoma. Visualizations are compared against traditional tissue preparation with histochemical staining. Preliminary clinical studies show comparable diagnostic quality between PARS histology and standard histology preparations. The proposed method is a milestone in this translational research project, aiming towards clinical deployment of a PARS microscope for skin cancer imaging.

We present the initial findings of two ML algorithms developed to automate reflectance confocal microscopy (RCM) of skin. On a retrospective test set of 141 pigmented lesions collected at MSKCC between 2011 and 2020, our DEJ detection algorithm identified the DEJ with a median precision of 3 “slices”. The algorithm was less precise on melanomas and on facial lesions. On a retrospective test set of 302 RCM mosaics, the segmentation algorithm identified nonspecific patterns with a sensitivity of 0.75 and specificity of 0.79. Prospectively, on 31 benign pigmented lesions, the DEJ detection algorithm was performed with a median precision of 6.18µm.

We present the initial results of two unsupervised out-of-distribution (OOD) detection algorithms, designed to flag dermoscopic images of lesions from classes not seen during training. When evaluated on the ISIC 2019 dataset - using 6 classes as in-distribution and 2 as OOD - the scores from our algorithms produced AUROC’s of 0.694/0.642. The images in ISIC 2019 mainly come from two datasets - HAM and BCN. When restricting our evaluation to consider only images from HAM the AUROC was 0.758/0.765, and when considering the images from BCN only, the AUROC dropped to 0.645/0.504.

Our group has recently reported on the development of a fast large area multiphoton exoscope (FLAME) for rapid macroscopic imaging with microscopic resolution of human skin. This imaging platform is based on multiphoton microscopy (MPM) that provide label-free, depth-resolved images by using femtosecond laser pulses. Our goal is to use FLAME for in vivo skin imaging to address unmet needs in clinical research and practice of dermatology. This work evaluates the photodamage threshold induced by the excitation laser for the full Fitzpatrick scale of human skin. The optimum laser power and scanning regimes for safe imaging determined by this study will be used for further in vivo clinical studies.

Aging alterations in dermal blood vessels have been investigated using Optical Coherence Tomography Angiography (OCTA). However, classifying the vessel’s type was previously limited. In this study, we focused on diameter-dependent vascular alterations in facial skin with age, developing 3D analytical methods to the OCTA data with removing tail-artifact. As a result, it was found that the number of micro-vessels, defined at 20–39 microns, decreased with age, which was inversely true for thick vessels (160–179 micron diameter). Our results suggest that the aging degree of dermal vessels may be uniquely assessed by the diameter-dependent vascular alterations using the OCTA.

The epidermis is of particular importance in cosmetology as it is considered to contribute greatly to the skin’s condition. Molecular vibrational signatures of the epidermis can be obtained using spectroscopic techniques. In my talk, I will give examples of visualizing water in 2D using near-infrared imaging. I will also introduce the latest results of our research of intracellular morphologies in the human epidermis during the epidermal differentiation process using stimulated Raman scattering (SRS) and water and intercellular lipid distribution in the human stratum corneum using coherent anti-Stokes Raman scattering (CARS).

Photonics has already produced numerous benefits for cosmetic laboratories, both for fundamental research and product performance evaluation. However, modern beauty industry presents to biophotonics a new challenge called customization. Today there is a high demand for fast and accurate diagnostic of skin and hair parameters, at home or in the boutique, to provide consumers with the tailored products. In this talk, we will present how the challenge of personalized skin diagnostic is addressed at L’Oréal, what products and services we are now able to propose thanks to photonics and what our latest challenges are.

Dermal blood vessels play a critical role in cutaneous homeostasis involved in the skin’s appearance. To elucidate the role of dermal vessels in skin beauty, we have been conducting many investigations with optical coherence tomography angiography (OCTA), whose use includes the analysis of skin’s superficial vascular plexuses. This presentation will highlight some of our results and show the effects of the following three factors on both skin vascularity and appearance: Short-term ultraviolet ray exposure, solar lentigo and facial aging. From our studies, future applications of OCTA may be beneficial in the cosmetic and medical fields.