This PDF file contains the front matter associated with SPIE Proceedings Volume 11618, including the Title Page, Copyright information, and Table of Contents.

Welcome and Introduction to SPIE Photonics West BiOS conference 11618: Photonics in Dermatology and Plastic Surgery 2021.

Please join us for a lively, interactive panel discussion with our AI in Dermatology speakers to hear their insights on the current state and future of AI for optical image analysis

We have developed a novel anti-vascular technique, termed photo-mediated ultrasound therapy (PUT), which utilizes nanosecond duration laser pulses synchronized with ultrasound bursts to remove microvasculature through cavitation. In this work, via the experiments in a rabbit ear model in vivo, the feasibility of PUT in the treatment of cutaneous microvessels was explored. Both the short-term effects and the long-term effects up to 4 weeks post-treatment were quantitatively assessed by measuring the perfusion rates of the vessels after treatment, showing that a single PUT treatment could significantly reduce blood perfusion. With unique advantages such as low laser fluence as compared with photothermolysis and agent-free treatment as compared with PDT, PUT holds potential to be developed into a new tool for the treatment of cutaneous vascular lesions.

We investigated the photothermal effect of near-infrared pulsed laser irradiation on collagen synthesis in fibroblasts in vitro to reduce complications in skin rejuvenation therapy by selective collagen heating. Tissue thermal damage with pain by laser heating of water is a problem in conventional laser skin rejuvenation therapy. To reduce these complications, we suggest heating collagen fibril selectively by applying selective photothermolysis. Laser parameters such as wavelength, pulse duration, pulse interval, and irradiance are important for selective heating. Fibroblasts will be heated gently by conducted heat from collagen fibril in our process, which enhances the expression of heat shock protein 47 (HSP47) in fibroblasts. This procedure would reduce pain and thermal damage on fibroblasts compared with the conventional procedure. In this study, we evaluated the amount of HSP47 content per living cell to investigate the photothermal effect on fibroblasts. The temperature distribution of the dermis during laser irradiation was simulated by the finite element method (FEM). 1480 and 1550 nm pulsed laser was irradiated to cultured fibroblasts. The laser emitted with a pulse duration of 100 μs, repetition of 2 kHz, fluence of 0 - 60 J/cm² , and irradiance of 0.5 W/cm² . To evaluate cell functional changes in time, ELISA and cell viability assay were performed 24 and 48 hours after laser irradiation.

Using a picosecond laser that delivers bursts of ultrashort pulses may improve thermal effects and limit side effects, compared to a sub-nanosecond laser. This study aims to analyse how the temperature increases on agar with or without black ink and on human skin. Results showed that large beams, and so long macropulses, present higher peaks of temperature than the small ones, as well as when fluencies and frequencies increase. Besides, higher thermal loading occurred with the nanosecond pulses. These results may explain why picosecond laser induces less side effects than sub-nanosecond laser.

Non-fractional lasers used for hair removal penetrate deep into the tissue (~4 mm), and can be repurposed for enhanced thermal delivery using topically applied indocyanine green (ICG), a highly absorptive NIR dye. We demonstrate a new methodology for achieving fractional damage with an 808nm diode laser using a microneedle array injector and ICG impregnated PLGA nanoparticle formulation. A comparison of the effects of injection depth and irradiation dose between free ICG and PLGA@ICG revealed that the nanoparticle formulation effectively concentrates and confines the fluorophore locally at depths of ~3mm and thermal damage is achieved with irradiances as low as 10J/cm2. These improvements in the delivery of ICG subcutaneously in a fractional pattern allow for confined dermal tissue injury using low irradiances, minimizing discoloration of superficial layers of the skin, and significantly enhancing the depth of thermal injury achievable with a wide-area non-fractional laser diode.

Optical coherence tomography (OCT) is a non-invasive diagnostic method that offers real-time visualization of the layered architecture of the skin in vivo. The 1.7-micron OCT system has been applied in cardiology, gynecology and dermatology, demonstrating an improved penetration depth in contrast to conventional 1.3-micron OCT. To further extend the capability, we developed a 1.7-micron OCT/OCT angiography (OCTA) system that allows for a visualization of both morphology and microvasculature in the deeper layers of the skin. Using this imaging system, we imaged human skin with different benign lesions and described the corresponding features of both structure and vasculature. The significantly improved imaging depth and additional functional information suggest that the 1.7-micron OCTA system has great potential to advance both dermatological clinical and research settings for characterization of benign and cancerous skin lesions.

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.

Mirau-type full-filed optical coherent tomography (FF-OCT) can provide imaging with cellular resolution section of human skin in vivo. In our previous work, the concept of dual-mode FF-OCT for cross-sectional (B-scan) and en face (E-scan) imaging with symmetrical illumination has been reported. This work presents a prototype of the dual-mode FF-OCT system and demonstrates the improvement of the efficiency for clinical applications. For clinical diagnosis, it is helpful to differentiate different types of nevus. Thus, an imaging tool capable of identifying the types of nevus is crucial. Our system can switch between two modes of imaging automatically by just clicking a button. The feature allows clinicians to explore the nevus more efficiently. While the B-scan images reveal the distribution of melanosomes, users can set a specific depth of the E-scan images to explore the morphology of surrounding skin cells instantly. The different types of nevus including junction nevus, intradermal nevus and compound nevus can be identified by using this dual-mode FF-OCT system.

The study is devoted to in vivo assessment of the vulvar tissue affected by lichen sclerosus and determining the severity of the disease by the state of connective tissue, blood flow and lymph flow using multimodal optical coherence tomography. This research will open up the possibility of developing and applying an effective noninvasive high-resolution method for visualization the state and depth of connective tissue lesions by scattering and polarization properties of the vulvar tissue, the blood flow and lymph flow based on the method of spectral multimodal OCT to assess the severity of lichen sclerosus. The in vivo OCT monitoring both the early dynamics of the response of all components of the vulvar tissue to low-level laser therapy (LLLT), and the degree of structure reparation after the treatment was carried out. Different response to LLLT was revealed: 3 of 10 patients had complete resolution of symptoms, 4 patients noted improvement in symptoms and 3 patients had no change in symptoms within 6 months of treatment and it was visualized by OCT.

Autologous keratinocytes or stem cell based therapies are modern approaches for the treatment of skin loss in burn victims and chronic wound patients. The aim of this study is to identify depth-resolved structural changes in treated burn wounds using Spatial Frequency Domain Imaging (SFDI). When altering the investigated depth into tissue via the spatial frequency used in our calculations, we found changes in the scattering parameters for the treated samples. These scattering changes are correlated with histology, indicating a potential means to monitor re-epithelization and collagen formation during the treatment process across the entire wound area.

While visual clinical impression is the standard of care for burn severity assessment, accuracy improves after the injury progresses, leading to patients waiting days for a diagnosis. Spatial Frequency Domain Imaging (SFDI) has shown the potential to assess burn grade as early as 24 hours post-burn. Here, we compared SFDI and Laser Speckle Imaging (LSI) at 24 and 72 hours after burn injury to clinical burn severity diagnosis. Three patients with burns ranging in severity were imaged. Both techniques showed an ability to categorize burn severity 24 hours after the initial injury, well before the outcome was determined by a clinician at 72 hours or later.

Spatial frequency domain imaging (SFDI) is a wide-field imaging technique that provides quantitative tissue optical property maps. We describe a compact, multi-aperture SFDI imager for burn severity evaluation. This was constructed using a CMOS sensor subdivided into multiple regions, each having a bandpass filter and objective lens. This compound-eye design enables simultaneous image acquisition at multiple wavelengths. The imager was evaluated using a rat burn model and compared to conventional SFDI devices that acquire wavelength data sequentially. The burns showed a decrease in the reduced scattering coefficient that is consistent with previously reported changes in full thickness burns.

The non-selective beta-blocker timolol has shown promising evidence for healing chronic, recalcitrant wounds, improving scar cosmesis, and expediting the completion of secondary intention. The purpose of our pilot study is to use clinical imaging, two-photon excitement fluorescence (TPF) and second harmonic generation (SHG) microscopy to evaluate the temporal and molecular effects of timolol vs. normal saline in Sprague-Dawley rats traumatized by 5-millimeter dermal punch biopsy. Initial findings suggest timolol delays wound contraction, but advanced imaging techniques may reveal novel collagenous or vascular mechanisms by which timolol is affecting acute wound healing.

Through vertex component analysis of hyperspectral imaging data in the visible spectral range, we differentiated erythematous and pigmented areas in patients with cutaneous chronic graft-versus-host disease. We explored the feasibility of hyperspectral imaging in combination with unsupervised learning algorithms to differentiate active disease from inactive post-inflammatory skin changes, a fundamental practice gap in caring for these patients. We compared erythema and pigment maps to the visual assessment by a dermatologist as the ground truth.

Complications of the diabetic foot proliferate from ischemic and/or neuropathic conditions in the form of excess tissue build-up or callus. Plantar calluses are thick and soft and form as a result of neuropathy at the toe apices and metatarsals head and/or toe tips. Neuro-ischemic calluses appear thin, hard, dry and/or glassy and typically form at the borders of the feet and/or on main weight bearing areas. It is standard practice for the clinician to remove this excess tissue to reduce pressure in the diabetic foot which reduces the risk of ulceration. The dead tissue layers are removed in a surgical process known as scalpel debridement, or chiropody. It is not uncommon for a clinician to encounter a buried wound in the process of scalpel debridement. However, the process itself is not straightforward in that the extent of debridement is not measurable between clinicians. The debridement process removes tissue up to the epidermal-dermal junction, which may be difficult to identify for an inexperienced clinician. In an effort to measure the effect of scalpel debridement, near infrared (NIR) imaging was applied in an IRB study between Florida International University and Dr. Mohan’s Diabetes Specialties Centre in Chennai, India. Subjects were assessed before and after the debridement procedure. NIR images at multiple wavelengths were obtained before and after debridement to estimate changes in tissue oxygenation in the callus and surrounding peri-callus regions. A method to analyze the significance of oxygenation change occurring both overall and within sub-quadrants of the callus is conducted to assess the effect of debridement. Measuring changes in tissue oxygenation may potentially be used in future clinical applications to improve the debridement process and reduce the risk of ulceration.

The American Cancer Society has estimated that a total of 1.8 million new cancer cases will arise in 2020, 15% percent of which are breast cancer. Radiation therapy (RT) is widely used post mastectomy or lumpectomy as a method of avoiding recurrence of disease in affected regions. Photon and proton therapy are among the main forms of RT currently applied to breast cancer patients. The effectiveness of photon vs proton therapy has been studied in various cancer models from differences in subjective clinical grading of radiation dermatitis (RD), a common side effect of RT. Herein, an objective physiological imaging approach using near-infrared optical techniques is implemented to quantitatively differentiate the effectiveness of proton vs photon therapy in breast cancer subjects undergoing RT. A 6-8 week longitudinal pilot study (WIRB approved) was carried out on 10 breast cancer subjects undergoing RT at Miami Cancer Institute (MCI). The chest wall, axilla, and lower neck were imaged on the irradiated and the non-irradiated (contralateral) sides of the torso to measure for tissue oxygenation changes. From preliminary analysis, it was observed that were distinct differences in tissue oxygenation and RD in the irradiated regions when compared to their contralateral nonirradiated tissue (reference). Changes in tissue oxygenation and skin toxicity (i.e. RD clinical grading) were more localized and less severe in subjects receiving proton therapy compared to photon therapy. Quantitative comparison of oxygenation changes and its correlation to the skin toxicity levels in photon vs proton therapy treated breast cancer subjects is currently carried out.

According to the American Cancer Society, it is projected that 1.8 million new cancer cases will arise. Of these new cases, 15% are expected to be Breast Cancer related. For many subjects undergoing radiation therapy (RT), radiation dermatitis (RD) is an unavoidable adverse reaction to necessary treatment. As much as 95% of RT subjects will experience RD during or after their treatment plan which can range from mild erythema to full necrosis of the treated tissue. Further complicating matters, the standard assessment approach for RD, the Common Terminology Criteria for Adverse Events (CTCAE), is subjective and relies on the treating clinician’s visual assessment. Assessment of oxygenated blood flow changes holds potential as a means of assessing the severity of RD. In this study, spatial-temporal changes of tissue oxygenation, via a breath-hold paradigm, were monitored in breast cancer subjects across weeks of RT using a near infrared imaging approach. Subjects were imaged dynamically to acquire 2D spatial-temporal maps of tissue oxygenation. A Pearson’s correlation-based approach was applied to spatial-temporal oxygenation maps to determine the extent of symmetry or asymmetry in oxygenated blood flow patterns. Current results indicate that the oxygenated blood flow in tissue regions neighboring the irradiated site are affected by radiation dermatitis. These results are significant as they infer that RT induces altered oxygenated blood flow that could potentially be correlated to RD severity, apart from static tissue oxygenation measurements.

Vitiligo is an immune skin disorder consisting of depigmented skin patches caused by the destruction of epidermal melanocytes. Vitiligo treatment represents a clinical challenge since the re-pigmentation mechanism is not fully understood. In this pilot study, we employ in-vivo multiphoton microscopy to evaluate epidermal keratinocyte metabolic state before and during treatment, in-vivo reflectance confocal microscopy to track melanocyte migration after treatment initiation, and single cell transcriptomics to identify unique cell populations more abundant in stable vitiligo lesions compared to normal skin. The findings provide insights into the role of certain cell populations in the viability of micro-grafting treatments.

To evaluate the effect of illumination, camera orientation, and camera distance on color consistency of different skin tones, several swatches from a Pantone SkinTone Guide deck were selected and photographed at varying distances, illuminations, and angles. The RGB values from each selected swatch from each image were converted to LAB units and compared with the converted “true” values provided by Pantone. The ability of various color references to correct different skin tones was tested by comparing color values from a subject’s forearm skin to “true” color values of the closest Pantone SkinTone swatch found by visual comparison.

Nonmelanoma skin cancers (NSMC) are among the most common malignancies in the US today. Mohs micrograph surgery (MMS) is the gold standard for most NSMC. However, MMS is time-consuming as it employs frozen section analysis (FSA) for intraoperative assessment. Each FSA can require up to 60 minutes per excision. Using photoacoustic remote sensing (PARS™) we demonstrate first results of imaging tissue morphology on human skin with a non-contact reflection-mode method, enabling rapid label-free pathological assessment. These images are validated against toluidine blue stained sections. The authors believe the proposed method represents a vital step towards an in-situ assessment of NSMC.

Basal cell carcinoma (BCC) is the most common skin cancer worldwide. In the diagnosis process million benign biopsies are performed annually, increasing morbidity and healthcare costs. Noninvasive in vivo technologies such as multiphoton microscopy (MPM) can reduce biopsies. We explored the potential of MPM to differentiate collagen changes associated with BCC and surrounding normal skin structures using quantitative analysis (Fast Fourier transformation and Integrated optical density using ImageJ software, and its CurveAlign and CT-FIRE fiber analysis plugins) on second harmonic generation images. Our results showed that collagen distribution is more aligned surrounding BCCs when compared to the skin normal structures, showing the feasibility of detecting BCC in a quantitative way. Our initial results are limited to a small number of samples therefore, large-scale studies are needed to validate these collagen analysis methods.

Multiphoton microscopy can provide sub-micron resolution images of living tissues in their native environment with chemical contrast. We recently reported on a fast large area multiphoton exoscope (FLAME) for rapidly mapping out macroscopic tissue areas (cm-scale) with microscopic resolution. In this presentation we demonstrate the imaging capability and the clinical utility of this system by performing a pilot study on ex vivo imaging of benign and malignant pigmented lesions of human skin. We identify morphological features such as cytological atypia, lentiginous hyperplasia, migration of melanocytes and demonstrate the value of sampling large tissue volumes for capturing the lesion heterogeneity.

Skin cancer, in all its various forms has been identified by the American Cancer Society as the most common form of cancer in both the United States and worldwide. In fact, more Americans will be diagnosed with skin cancer than all other forms of cancer combined. Typically, initial skin cancer diagnosis relies on the asymmetry, border, core, diameter, and evolution (ABCDE) test. As a subjective test, the ABCDE method relies on the skill of the practitioner to provide an accurate diagnosis. Therefore, a diagnostic instrument that could be used as an initial screening tool to determine whether a skin lesion is potentially cancerous would have significant application. This need is especially acute in under-served communities without ready-access to skilled practitioners. It also could have widespread applicability at the point-of-care to reduce the strain on clinical dermatologists. We have recently demonstrated preliminary results showing the capability to discriminate between healthy skin and cancerous lesions using an infrared method inspired by human color vision. This technique relies on identifying variations in the infrared (IR) spectra of healthy and cancerous tissue; however, unlike standard IR-spectroscopic sensing methods it does not require the use of a spectrometer. Rather, this approach utilizes the response through three IR optical filters; similar to the method that human eye uses to discriminate between hundreds of thousands of colors in the natural world. Here, we report on calculated studies demonstrating the selectivity of this approach for various types of cancerous lesions including melanomas. We explore various potential optical filter sets to discriminate not only between healthy and cancerous tissue, but also to determine whether it may be possible to discriminate between various types of melanoma lesions using this bioinspired method. These results demonstrate that this approach has potential as a low-cost, widely deployed sensing method for detection of cancerous skin lesions, prior to examination by a trained specialist.

Inflammatory skin disorder, eczema, is usually assessed by subjective disease scoring systems such as SCORAD and EASI. These scoring systems are based on clinical observations and questionnaires and hence it is subjected to inter and intra-assessor variability. Here, for the first time, we used optoacoustic imaging to image the structural and morphological changes of the skin in a non-invasive manner. Through a clinical study, we computed specific metrics such as epidermis thickness, total blood volume, vessel diameter in the dermis, ratio of low and high frequency signals. We trained a linear kernel-based support vector machine model for eczema classification using these metrics. We could achieve an accuracy of 86.6% and high sensitivity and specificity of 96.2% and 82.1% respectively. We also formulated a novel Eczema Vascular and Structural Index (EVSI) to objectively assess the severity of eczema.

Spatial frequency domain imaging (SFDI) is a wide-field spectral imaging technique that can be used to characterize optical properties of in-vivo tissue. Typically, SFDI uses light transport modeling based on Monte Carlo simulations to analyze the detected diffuse reflectance. Here, we examined the effect of using a semi-infinite homogeneous tissue model to determine optical properties of in-vivo human skin across a full range of pigmentation levels. We analyzed µs’ curves and performed correlation analysis between µs’ and degree of pigmentation determined using a tristimulus colorimeter. Our results suggested that pigmentation’s effect on µs’ is minimal at near-infrared wavelengths.

Spatial Frequency Domain Imaging (SFDI) is a non-invasive diffuse optical imaging technology that quantifies tissue optical properties by projecting spatially modulated light onto a region of interest. By detecting and fitting the diffuse reflectance to a light transport model, tissue absorption (μ_a) and scattering (μ_s') coefficients are calculated. However, when measuring skin, bulk μ_a and μ_s' from a homogeneous light transport model may not correspond with the actual properties of individual skin layers, especially for highly pigmented skin. To obtain physiologically accurate skin optical property values, we propose an iterative method based on a two- layered Monte Carlo model. We initially assume that μ_s' in darker skin is the same as that in lighter skin, and set the epidermal a as the free parameter when fitting the diffuse reflectance. To test this algorithm, we analyzed data from the forearms of 6 subjects having various levels of pigmentation, at 8 visible-to-near-infrared wavelengths. We compared the measured reflectance to both the homogeneous model and our layered model to quantify fit accuracy. At 471 nm and 526 nm for patients of Fitzpatrick skin types IV-VI (relatively dark skin), the two-layered model provided a 10-20% improvement in fit to the AC reflectance as a function of spatial frequency, compared to the homogeneous model. These improved fits yielded epidermal absorption coefficients that were notably higher than the bulk μ_a from the homogeneous model. Fitting the extracted epidermal μ_a to a melanin extinction spectrum¹ enabled estimation of the melanin concentration in the epidermis.

This Conference Presentation, “Noninvasive quantification of cutaneous inflammation with hyperspectral short wave infrared imaging,” was recorded for the Photonics West 2021 Digital Forum.

Dermoscopy is a non-invasive skin imaging technique that permits visualization of features of pigmented melanocytic neoplasms that are not discernable by examination with the naked eye. While studies on the automated analysis of dermoscopy images date back to the mid-1990s, because of various factors (lack of publicly available datasets, open-source software, computational power, etc.), the field progressed rather slowly in its first two decades. With the release of a large public dataset by the International Skin Imaging Collaboration in 2016, development of open-source software for convolutional neural networks, and the availability of inexpensive graphics processing units, dermoscopy image analysis has recently become a very active research field. In this talk, I will first present a historical overview of dermoscopy image analysis and then discuss the latest developments in this field that were prompted by the deep learning revolution.

This Conference Presentation, “Computational optics of the collagen rich tumor microenvironment,” was recorded for the Photonics West 2021 Digital Forum.

Machine learning in reflectance confocal imaging for aiding cancer diagnosis: opportunities and challenges

Adequate resuscitation is critical for burn wound patients where the affected total body surface area (TBSA) exceeds 20%, as fluid loss leads to organ failure, shock, and patient mortality. Protocols have been developed to combat fluid loss, however excess fluids can also lead to compartment syndromes. Here, we used spatial frequency domain imaging (SFDI), a non-contact wide field imaging technique to measure in-vivo water changes in a 40 % TBSA porcine burn model. In this pilot study one pig received intravenous fluids according to the Parkland formula on top of enteral fluid resuscitation, while a second pig received no fluids during the experiment. Unburned regions of skin were imaged with SFDI from 3 to 22 hours post-burn. This imaging technique uses structured illumination, projected at multiple spatial frequencies and wavelengths, to measure tissue reflectance, which is used to obtain the reduced scattering and absorption coefficients. Water fraction is based upon absorption in the near-infrared spectrum at 971 nm, where water has a high extinction coefficient. SFDI measurements of superficial tissue hydration showed increased water fraction for the pig that received fluid resuscitation (+17%), and a decrease for the pig that received no fluids (-5%). Analysis showed decreased scattering measured in the pig that received fluids (+13%), suggesting increased interstitial water pressure. These preliminary results are consistent with systemic hydration, as estimated based on CT-measured subcutaneous fat thickness. SFDI may, therefore offer the possibility of non-invasively monitoring fluid resuscitation of large TBSA patients.