In Vivo Imaging Techniques for the Human Scalp: A Systematic Review of the Literature

OBJECTIVE

Scalp inflammation and alopecia are distressing conditions for which patients regularly present to dermatology. Although some diagnoses can be made clinically, others require biopsy, which carries the risk of pain, infection, bleeding, and scarring. This review examines the existing literature regarding noninvasive in vivo imaging techniques and their evidence and utility in evaluating scalp pathology, with a focus on the diagnostics of hair conditions.

METHODS

A systematic literature search was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines without timeframe restrictions. The PubMed and Clarivate (Web of Science) databases were searched using the terms ("imaging" OR "in-vivo imaging" OR "non-invasive imaging" OR "non-invasive in vivo imaging" "imaging," "in-vivo imaging) AND ("human scalp disorders" OR "scalp" OR "hair loss" OR "alopecia"). Peer-reviewed randomized control trials (RCTs), prospective studies, retrospective studies, and case series or reports discussing in vivo imaging of the scalp published before 2022 were selected.

RESULTS

Forty-two studies were included and discussed; modalities included laser devices (n = 27), ultrasound (US) (n = 13), infrared thermography (n = 1), skin capacitance imaging (SCI), and ultraviolet light-enhanced visualization (ULEV) (n = 1). The most common laser devices used were reflectance confocal microscopy (RCM), multiphoton microscopy (MPM), and optical coherence tomography (OCT). US techniques included high-frequency US (HFUS) and US biomicroscopy (UBM).

CONCLUSION

Quality imaging of the scalp in the setting of alopecic, neoplastic, and inflammatory diseases is highly sought after. Many of these noninvasive imaging techniques show promise, each with individual advantages and disadvantages in imaging-specific conditions. Ultimately, noninvasive imaging techniques may be used to optimize patient management and minimize morbidity associated with scalp biopsies.

Potential rapid intraoperative cancer diagnosis using dynamic full-field optical coherence tomography and deep learning: A prospective cohort study in breast cancer patients

An intraoperative diagnosis is critical for precise cancer surgery. However, traditional intraoperative assessments based on hematoxylin and eosin (H&E) histology, such as frozen section, are time-, resource-, and labor-intensive, and involve specimen-consuming concerns. Here, we report a near-real-time automated cancer diagnosis workflow for breast cancer that combines dynamic full-field optical coherence tomography (D-FFOCT), a label-free optical imaging method, and deep learning for bedside tumor diagnosis during surgery. To classify the benign and malignant breast tissues, we conducted a prospective cohort trial. In the modeling group (n = 182), D-FFOCT images were captured from April 26 to June 20, 2018, encompassing 48 benign lesions, 114 invasive ductal carcinoma (IDC), 10 invasive lobular carcinoma, 4 ductal carcinoma in situ (DCIS), and 6 rare tumors. Deep learning model was built up and fine-tuned in 10,357 D-FFOCT patches. Subsequently, from June 22 to August 17, 2018, independent tests (n = 42) were conducted on 10 benign lesions, 29 IDC, 1 DCIS, and 2 rare tumors. The model yielded excellent performance, with an accuracy of 97.62%, sensitivity of 96.88% and specificity of 100%; only one IDC was misclassified. Meanwhile, the acquisition of the D-FFOCT images was non-destructive and did not require any tissue preparation or staining procedures. In the simulated intraoperative margin evaluation procedure, the time required for our novel workflow (approximately 3 min) was significantly shorter than that required for traditional procedures (approximately 30 min). These findings indicate that the combination of D-FFOCT and deep learning algorithms can streamline intraoperative cancer diagnosis independently of traditional pathology laboratory procedures.

Bichromatic tetraphasic full-field optical coherence microscopy

Significance

Full-field optical coherence microscopy (FF-OCM) is a prevalent technique for backscattering and phase imaging with epi-detection. Traditional methods have two limitations: suboptimal utilization of functional information about the sample and complicated optical design with several moving parts for phase contrast.

Aim

We report an OCM setup capable of generating dynamic intensity, phase, and pseudo-spectroscopic contrast with single-shot full-field video-rate imaging called bichromatic tetraphasic (BiTe) full-field OCM with no moving parts.

Approach

BiTe OCM resourcefully uses the phase-shifting properties of anti-reflection (AR) coatings outside the rated bandwidths to create four unique phase shifts, which are detected with two emission filters for spectroscopic contrast.

Results

BiTe OCM overcomes the disadvantages of previous FF-OCM setup techniques by capturing both the intensity and phase profiles without any artifacts or speckle noise for imaging scattering samples in three-dimensional (3D). BiTe OCM also utilizes the raw data effectively to generate three complementary contrasts: intensity, phase, and color. We demonstrate BiTe OCM to observe cellular dynamics, image live, and moving micro-animals in 3D, capture the spectroscopic hemodynamics of scattering tissues along with dynamic intensity and phase profiles, and image the microstructure of fall foliage with two different colors.

Conclusions

BiTe OCM can maximize the information efficiency of FF-OCM while maintaining overall simplicity in design for quantitative, dynamic, and spectroscopic characterization of biological samples.

Dynamic full-field optical coherence tomography module adapted to commercial microscopes allows longitudinal in vitro cell culture study

Dynamic full-field optical coherence tomography (D-FFOCT) has recently emerged as a label-free imaging tool, capable of resolving cell types and organelles within 3D live samples, whilst monitoring their activity at tens of milliseconds resolution. Here, a D-FFOCT module design is presented which can be coupled to a commercial microscope with a stage top incubator, allowing non-invasive label-free longitudinal imaging over periods of minutes to weeks on the same sample. Long term volumetric imaging on human induced pluripotent stem cell-derived retinal organoids is demonstrated, highlighting tissue and cell organization processes such as rosette formation and mitosis as well as cell shape and motility. Imaging on retinal explants highlights single 3D cone and rod structures. An optimal workflow for data acquisition, postprocessing and saving is demonstrated, resulting in a time gain factor of 10 compared to prior state of the art. Finally, a method to increase D-FFOCT signal-to-noise ratio is demonstrated, allowing rapid organoid screening.

Dynamic full-field optical coherence tomography for live-cell imaging and growth-phase monitoring in Aspergillus fumigatus

Introduction

The diagnosis of cutaneous manifestations of deep mycoses relies on both histopathological and direct examinations. Yet, the current diagnostic criteria cannot prevent missed cases, including invasive aspergillosis, which requires the development of a novel diagnostic approach and imaging tools. We recently introduced the use of dynamic full-field optical coherence tomography (D-FF-OCT) in fungal diagnostics with a definition approaching that of conventional microscopy and the ability to return metabolic information regarding different fungal species. The present work focuses on subcellular dynamics and live-cell imaging of Aspergillus fumigatus with D-FF-OCT to follow the fungal growth stages.

Methods

The A. fumigatus ATCC 204305 quality-control strain was used for all imaging experiments, following incubation times varying between 24 and 72 h at 30°C in a humidified chamber on Sabouraud dextrose agar. Fungal growth was subsequently monitored with D-FF-OCT for up to 5 h at room temperature and following the pharmacological stress of either voriconazole, amphotericin B, or caspofungin gradient concentration.

Results

D-FF-OCT images allow not only the visualization of intracellular trafficking of vacuoles but also an evolving dynamic segmentation of conidiophores depending on the chronological development and aging of the hyphae or the effect of antifungal treatment. The same applies to conidial heads, with the most intense D-FF-OCT signal coming from vesicles, revealing a changing dynamic within a few hours only, as well as complete extinction following subsequent drying of the Sabouraud dextrose agar.

Discussion

These results provide additional data on the ability of D-FF-OCT to monitor some of the main life cycle processes, dynamics, and intracellular trafficking of vacuoles in A. fumigatus, with or without the effect of pharmacological stress. Such complementary metabolic information could help both clinicians and microbiologists in either mechanistic studies toward experimental mycology or the development of a potential D-FF-OCT-guided diagnosis of superficial fungal infections.

Interface self-referenced dynamic full-field optical coherence tomography

Dynamic full-field optical coherence tomography (D-FFOCT) has recently emerged as an invaluable live label-free and non-invasive imaging modality able to image subcellular biological structures and their metabolic activity within complex 3D samples. However, D-FFOCT suffers from fringe artefacts when imaging near reflective surfaces and is highly sensitive to vibrations. Here, we present interface Self-Referenced (iSR) D-FFOCT, an alternative configuration to D-FFOCT that takes advantage of the presence of the sample coverslip in between the sample and the objective by using it as a defocused reference arm, thus avoiding the aforementioned artefacts. We demonstrate the ability of iSR D-FFOCT to image 2D fibroblast cell cultures, which are among the flattest mammalian cells.

Erbium:YAG fractional laser ablation improves cutaneous delivery of pentoxifylline from different topical dosage forms

Topical application of pentoxifylline (PTX) would enable targeted treatment of radiation-induced skin fibrosis. However, PTX is hydrophilic with limited partitioning into the stratum corneum. The objective of this study was to investigate whether use of Erbium:YAG fractional laser ablation and different topical dosage forms (solution, hydrogel and patch) could be used to improve PTX cutaneous delivery as opposed to transdermal permeation. Initial results confirmed that fractional laser ablation significantly increased PTX delivery from each dosage form compared to passive controls. Delivery efficiencies of ∼30% were achieved with each dosage form but a large proportion of PTX permeated across the skin; thus, fluences were decreased to create shallower micropores, their depth being linearly dependent on fluence. The hydrogel was selected as the optimal formulation and PTX delivery efficiencies were further increased (44%-67%) by reducing the amount of hydrogel applied (better mimicking conditions of use). As this resulted in PTX depletion in the formulation, a loss of dependence of delivery on laser fluence was observed. These findings suggest that fractional laser ablation at moderate fluences enables an effective and targeted cutaneous delivery of PTX from a hydrogel formulation, which can be easily produced without the need for complex equipment.

Optical coherence tomography holds promise to transform the diagnostic anatomic pathology gross evaluation process

SIGNIFICANCE

Real-time histology can close a variety of gaps in tissue diagnostics. Currently, gross pathology analysis of excised tissue is dependent upon visual inspection and palpation to identify regions of interest for histopathological processing. Such analysis is limited by the variable correlation between macroscopic and microscopic findings. The current standard of care is costly, burdensome, and inefficient.

AIM

We are the first to address this gap by introducing optical coherence tomography (OCT) to be integrated in real-time during the pathology grossing process.

APPROACH

This is achieved by our high-resolution, ultrahigh-speed, large field-of-view OCT device designed for this clinical application.

RESULTS

We demonstrate the feasibility of imaging tissue sections from multiple human organs (breast, prostate, lung, and pancreas) in a clinical gross pathology setting without interrupting standard workflows.

CONCLUSIONS

OCT-based real-time histology evaluation holds promise for addressing a gap that has been present for >100 years.

Updated Role of High-frequency Ultrasound in Assessing Dermatological Manifestations in Autoimmune Skin Diseases

Autoimmune skin diseases are a group of disorders that arise due to the dysregulated immune system attacking self-antigens, causing multiple tissue and organ lesions. With disease progression, the physical and psychological health of patients may be seriously damaged. High-frequency ultrasound is non-invasive, reproducible, and suitable for visualizing the fine structure of external organs. The usage of high-frequency ultrasound has increased in recent years in the auxiliary diagnosis and monitoring of various skin diseases; it serves as a promising tool for dermatological disease assessment. This review summarizes the characteristics of high-frequency ultrasound imaging in common autoimmune skin diseases, including systemic lupus erythematosus, scleroderma, psoriasis, dermatomyositis, and pemphigus/pemphigoid. The objective of this review is to provide new ideas and strategies for dermatologists to diagnose and track the prognosis of autoimmune skin diseases.

Dynamic full-field optical coherence tomography as complementary tool in fungal diagnostics

Histopathology and microscopic examination of infected tissue are the gold standards to prove the diagnosis of invasive fungal infection (IFI). Yet, they suffer from essential limitations that hamper rapid diagnosis and require the future development of new imaging tools dedicated to fungal diagnostics. To this end, the present work introduces the first use of dynamic full-field optical coherence tomography (D-FF-OCT) for the visualization of microscopic filamentous fungi. Data collected from the observation of three different fungal species (Nannizzia gypsea, Aspergillus fumigatus and Rhizopus arrhizus) confirm the ability of D-FF-OCT to visualize not only the main structures of all selected fungal species (hyphae, spores, conidia, sporulating structures), but also the metabolic activity of the organisms, which could provide additional help in the future to better characterize the signature of each fungal structure. These results demonstrate how D-FF-OCT could serve as potential complementary tool for rapid diagnosis of IFI in both intensive and non-intensive care units.

Methods and applications of full-field optical coherence tomography: a review

SIGNIFICANCE

Full-field optical coherence tomography (FF-OCT) enables en face views of scattering samples at a given depth with subcellular resolution, similar to biopsy without the need of sample slicing or other complex preparation. This noninvasive, high-resolution, three-dimensional (3D) imaging method has the potential to become a powerful tool in biomedical research, clinical applications, and other microscopic detection.

AIM

Our review provides an overview of the disruptive innovations and key technologies to further improve FF-OCT performance, promoting FF-OCT technology in biomedical and other application scenarios.

APPROACH

A comprehensive review of state-of-the-art accomplishments in OCT has been performed. Methods to improve performance of FF-OCT systems are reviewed, including advanced phase-shift approaches for imaging speed improvement, methods of denoising, artifact reduction, and aberration correction for imaging quality optimization, innovations for imaging flux expansion (field-of-view enlargement and imaging-depth-limit extension), new implementations for multimodality systems, and deep learning enhanced FF-OCT for information mining, etc. Finally, we summarize the application status and prospects of FF-OCT in the fields of biomedicine, materials science, security, and identification.

RESULTS

The most worth-expecting FF-OCT innovations include combining the technique of spatial modulation of optical field and computational optical imaging technology to obtain greater penetration depth, as well as exploiting endogenous contrast for functional imaging, e.g., dynamic FF-OCT, which enables noninvasive visualization of tissue dynamic properties or intracellular motility. Different dynamic imaging algorithms are compared using the same OCT data of the colorectal cancer organoid, which helps to understand the disadvantages and advantages of each. In addition, deep learning enhanced FF-OCT provides more valuable characteristic information, which is of great significance for auxiliary diagnosis and organoid detection.

CONCLUSIONS

FF-OCT has not been completely exploited and has substantial growth potential. By elaborating the key technologies, performance optimization methods, and application status of FF-OCT, we expect to accelerate the development of FF-OCT in both academic and industry fields. This renewed perspective on FF-OCT may also serve as a road map for future development of invasive 3D super-resolution imaging techniques to solve the problems of microscopic visualization detection.

External-cavity laser diode using acousto-optic deflector as tunable grating

In this study, a novel, to the best of our knowledge, external-cavity laser diode (ECLD) without a diffraction grating is proposed and demonstrated. In the proposed configuration, an acousto-optic deflector (AOD) acts not only as a deflector but also as a diffraction grating. Thus, the AOD functions as a wavelength-selective device, which helps improve the overall performance of the ECLD. In fact, the proposed configuration realizes a wide range of wavelength scanning with a simple configuration, highly efficient optical feedback, and a steady optical resonator with a constant cavity length. We confirm that the wavelengths scanned with the proposed ECLD agree well with theoretical calculations. The scanning range and maximum frequency response reached approximately 60 nm and 50 kHz, respectively. Moreover, reproducible measurements of the three-dimensional thickness distribution of a thin glass plate indicates that the proposed ECLD can be used for optical coherence tomography imaging systems.

Classification of Basal Cell Carcinoma in Ex Vivo Confocal Microscopy Images from Freshly Excised Tissues Using a Deep Learning Algorithm

Ex vivo confocal microscopy (EVCM) generates digitally colored purple-pink images similar to H&E without time-consuming tissue processing. It can be used during Mohs surgery for rapid detection of basal cell carcinoma (BCC); however, reading EVCM images requires specialized training. An automated approach using a deep learning algorithm for BCC detection in EVCM images can aid in diagnosis. A total of 40 BCCs and 28 negative (not-BCC) samples were collected at Memorial Sloan Kettering Cancer Center to create three training datasets: (i) EVCM image dataset (663 images), (ii) H&E image dataset (516 images), and (iii) a combination of the two datasets. A total of seven BCCs and four negative samples were collected to create an EVCM test dataset (107 images). The model trained with the EVCM dataset achieved 92% diagnostic accuracy, similar to the H&E model (93%). The area under the receiver operator characteristic curve was 0.94, 0.95, and 0.94 for EVCM-, H&E-, and combination-trained models, respectively. We developed an algorithm for automatic BCC detection in EVCM images (comparable accuracy to dermatologists). This approach could be used to assist with BCC detection during Mohs surgery. Furthermore, we found that a model trained with only H&E images (which are more available than EVCM images) can accurately detect BCC in EVCM images.

Classification of squamous cell carcinoma from FF-OCT images: Data selection and progressive model construction

We investigate the speed and performance of squamous cell carcinoma (SCC) classification from full-field optical coherence tomography (FF-OCT) images based on the convolutional neural network (CNN). Due to the unique characteristics of SCC features, the high variety of CNN, and the high volume of our 3D FF-OCT dataset, progressive model construction is a time-consuming process. To address the issue, we develop a training strategy for data selection that makes model training 16 times faster by exploiting the dependency between images and the knowledge of SCC feature distribution. The speedup makes progressive model construction computationally feasible. Our approach further refines the regularization, channel attention, and optimization mechanism of SCC classifier and improves the accuracy of SCC classification to 87.12% at the image level and 90.10% at the tomogram level. The results are obtained by testing the proposed approach on an FF-OCT dataset with over one million mouse skin images.

Dermal epidermal junction detection for full-field optical coherence tomography data of human skin by deep learning

Full-field optical coherence tomography (FF-OCT) has been developed to obtain three-dimensional (3D) OCT data of human skin for early diagnosis of skin cancer. Detection of dermal epidermal junction (DEJ), where melanomas and basal cell carcinomas originate, is an essential step for skin cancer diagnosis. However, most existing DEJ detection methods consider each cross-sectional frame of the 3D OCT data independently, leaving the relationship between neighboring frames unexplored. In this paper, we exploit the continuity of 3D OCT data to enhance DEJ detection. In particular, we propose a method for noise reduction of the training data and a multi-directional convolutional neural network to predict the probability of epidermal pixels in the 3D OCT data, which is more stable than one-directional convolutional neural network for DEJ detection. Our crosscheck refinement method also exploits the domain knowledge to generate a smooth DEJ surface. The average mean error of the entire DEJ detection system is approximately 6 μm.

Full-field spectral-domain optical interferometry for snapshot three-dimensional microscopy

Prevalent techniques in label-free linear optical microscopy are either confined to imaging in two dimensions or rely on scanning, both of which restrict their applications in imaging subtle biological dynamics. In this paper, we present the theoretical basis along with demonstrations supporting that full-field spectral-domain interferometry can be used for imaging samples in 3D with no moving parts in a single shot. Consequently, we propose a novel optical imaging modality that combines low-coherence interferometry with hyperspectral imaging using a light-emitting diode and an image mapping spectrometer, called Snapshot optical coherence microscopy (OCM). Having first proved the feasibility of Snapshot OCM through theoretical modeling and a comprehensive simulation, we demonstrate an implementation of the technique using off-the-shelf components capable of capturing an entire volume in 5 ms. The performance of Snapshot OCM, when imaging optical targets, shows its capability to axially localize and section images over an axial range of ±10 µm, while maintaining a transverse resolution of 0.8 µm, an axial resolution of 1.4 µm, and a sensitivity of up to 80 dB. Additionally, its performance in imaging weakly scattering live cells shows its capability to not only localize the cells in a densely populated culture but also to generate detailed phase profiles of the structures at each depth for long durations. Consolidating the advantages of several widespread optical microscopy modalities, Snapshot OCM has the potential to be a versatile imaging technique for a broad range of applications.

Comparison of full-field optical coherence tomography imaging for pancreatic tissue sample obtained by EUS-fine-needle biopsy and conventional histological examination: A study protocol for a prospective trial

For a definitive diagnosis of fine-needle aspiration (FNA)/biopsy, one of the reliable techniques to determine the adequacy and accuracy rapid on-site evaluation (ROSE) of cytological samples is preferable. Because of the lack of trained pathologists, alternatives have to be explored. This study is primarily conducted to determine the diagnostic sensitivity and specificity of full-field optical coherence tomography (FF-OCT) and secondarily to evaluate the possibility of FF-OCT differentiating different types of pancreatic diseases. The diagnostic coherence of FF-OCT by a trained assistant (endoscopist) and trained pathologist is also compared. This is a single-center, prospective, observation trial. Eighty patients would be enrolled in the study. The tissue samples acquired by endoscopic ultrasound fine-needle biopsy (EUS-FNB) would be imaged by the FF-OCT system, interpreted by a trained endoscopist and a pathologist. The results of the image interpretation would be verified with histological findings. This study determines the diagnostic capability of FF-OCT as a ROSE technique while performing EUS-FNB, and whether endoscopists can implement the assessment.

Full-field optical coherence tomography for the diagnosis of giant cell arteritis

Histopathological examination of temporal artery biopsy (TAB) remains the gold standard for the diagnosis of giant cell arteritis (GCA) but is associated with essential limitations that emphasize the need for an upgraded pathological process. This study pioneered the use of full-field optical coherence tomography (FF-OCT) for rapid and automated on-site pathological diagnosis of GCA. Sixteen TABs (12 negative and 4 positive for GCA) were selected according to major histopathological criteria of GCA following hematoxylin-eosin-saffron-staining for subsequent acquisition with FF-OCT to compare structural modifications of the artery cell wall and thickness of each tunica. Gabor filtering of FF-OCT images was then used to compute TAB orientation maps and validate a potential automated analysis of TAB sections. FF-OCT allowed both qualitative and quantitative visualization of the main structures of the temporal artery wall, from the internal elastic lamina to the vasa vasorum and red blood cells, unveiling a significant correlation with conventional histology. FF-OCT imaging of GCA TABs revealed destruction of the media with distinct remodeling of the whole arterial wall into a denser reticular fibrous neo-intima, which is distinctive of GCA pathogenesis and accessible through automated Gabor filtering. Rapid on-site FF-OCT TAB acquisition makes it possible to identify some characteristic pathological lesions of GCA within a few minutes, paving the way for potential machine intelligence-based or even non-invasive diagnosis of GCA.

Er:YAG fractional laser ablation for cutaneous co-delivery of pentoxifylline and d-α-tocopherol succinate: A new approach for topical treatment of radiation-induced skin fibrosis

Radiation induced fibrosis is a common side-effect after radiotherapy. Pentoxifylline is reported to reverse radiation injuries when used in conjunction with D-α-tocopherol. However, pentoxifylline has a short half-life, limited oral bioavailability, and induces several systemic adverse effects. The objective of this study was to investigate the feasibility of using Er:YAG fractional laser ablation to enable simultaneous cutaneous delivery of pentoxifylline and D- α -tocopherol succinate from poly(lactide-co-glycolide) microparticles prepared using the freeze-fracture technique. In vitro release experiments demonstrated the different release profiles of the two molecules, which were influenced by their very different lipophilicities and aqueous solubilities. Experiments were then performed to investigate the effect of laser fluence on pore depth and so determine the pore volume available to host the topically applied microparticles. Application of the pentoxifylline and D-α-tocopherol succinate containing microparticles, prepared with RESOMER® RG 502H, to laser porated skin for 48 h, resulted in simultaneous delivery of pentoxifylline (69.63 ± 6.41 μg/cm²; delivery efficiency 46.4%) and D-α-tocopherol succinate (33.25 ± 8.91 μg/cm²; delivery efficiency 22.2%). After deposition into the micropores, the poly(lactide-co-glycolide) microparticles containing pentoxifylline and D-α-tocopherol succinate could serve as an intraepidermal depot to enable sustained drug delivery after micropore closure and thereby reduce the need for repeated microporation.

A compact high-speed full-field optical coherence microscope for high-resolution in vivo skin imaging

A compact high-speed full-field optical coherence microscope has been developed for high-resolution in vivo imaging of biological tissues. The interferometer, in the Linnik configuration, has a size of 11 × 11 × 5 cm³ and a weight of 210 g. Full-field illumination with low-coherence light is achieved with a high-brightness broadband light-emitting diode. High-speed full-field detection is achieved by using part of the image sensor of a high-dynamic range CMOS camera. En face tomographic images are acquired at a rate of 50 Hz, with an integration time of 0.9 ms. The image spatial resolution is 0.9 μm × 1.2 μm (axial × transverse), over a field of view of 245 × 245 μm² . Images of human skin, revealing in-depth cellular-level structures, were obtained in vivo and in real-time without the need for stabilization of the subject. The system can image larger fields, up to 1 × 1 mm² , but at a reduced depth.

Confocal Fluorescence Microscopy Platform Suitable for Rapid Evaluation of Small Fragments of Tissue in Surgical Pathology Practice

CONTEXT.—

Rapid advances in the fields of biophotonics, computer science, and instrumentation have allowed for high-resolution imaging of biologic tissues.

OBJECTIVE.—

To evaluate the quality of images from an optimized confocal fluorescence microscopy (CFM) platform for rapid evaluation of small fragments of tissue, compared with hematoxylin-eosin staining.

DESIGN.—

Tissue fragments (up to 1.0 × 0.3 cm) were stained with 0.6 mM acridine orange for 60 seconds and imaged using a CFM platform at 488-nm and 785-nm wavelength. The imaged tissues were then fixed in formalin and processed to generate hematoxylin-eosin-stained tissue sections. The quality of CFM images was scored on a scale of 0 to 3 on the basis of the percentage of the CFM images with recognizable tissue architecture (0, 0%; 1, <20%; 2, 20%-50%; 3, >50%). The diagnoses made using CFM images were compared with those made using histopathologic analysis of the hematoxylin-eosin-stained tissue sections.

RESULTS.—

We imaged 118 tissue fragments obtained from 40 breast, 23 lung, 39 kidney, and 16 liver surgical excision specimens. We acquired CFM images in 2 to 3 minutes; 95.8% (113 of 118) of images showed a quality score of 3, and 4.2% (5 of 118) had a score of 2. We achieved a sensitivity of 95.5%, specificity of 97.3%, positive predictive value of 95.5%, and negative predictive value of 97.3%.

CONCLUSIONS.—

Our results demonstrate the suitability of the CFM platform for rapid and accurate evaluation of small tissue fragments in surgical pathology practice.

Line-field confocal optical coherence tomography for high-resolution noninvasive imaging of skin tumors

An optical technique called line-field confocal optical coherence tomography (LC-OCT) is introduced for high-resolution, noninvasive imaging of human skin in vivo. LC-OCT combines the principles of time-domain optical coherence tomography and confocal microscopy with line illumination and detection using a broadband laser and a line-scan camera. LC-OCT measures the echo-time delay and amplitude of light backscattered from cutaneous microstructures through low-coherence interferometry associated with confocal spatial filtering. Multiple A-scans are acquired simultaneously while dynamically adjusting the focus. The resulting cross-sectional B-scan image is produced in real time at 10  frame  /  s. With an isotropic spatial resolution of ∼1  μm, the LC-OCT images reveal a comprehensive structural mapping of skin at the cellular level down to a depth of ∼500  μm. LC-OCT has been applied to the imaging of various skin lesions, in vivo, including carcinomas and melanomas. LC-OCT images are found to strongly correlate with conventional histopathological images. The use of LC-OCT as an adjunct tool in medical practice could significantly improve clinical diagnostic accuracy while reducing the number of biopsies of benign lesions.

Extracting Blood Vessels From Full-Field OCT Data of Human Skin by Short-Time RPCA

Recent advances in optical coherence tomography (OCT) lead to the development of OCT angiography to provide additional helpful information for diagnosis of diseases like basal cell carcinoma. In this paper, we investigate how to extract blood vessels of human skin from full-field OCT (FF-OCT) data using the robust principal component analysis (RPCA) technique. Specifically, we propose a short-time RPCA method that divides the FF-OCT data into segments and decomposes each segment into a low-rank structure representing the relatively static tissues of human skin and a sparse matrix representing the blood vessels. The method mitigates the problem associated with the slow-varying background and is free of the detection error that RPCA may have when dealing with FF-OCT data. Both short-time RPCA and RPCA methods can extract blood vessels from FF-OCT data with heavy speckle noise, but the former takes only half the computation time of the latter. We evaluate the performance of the proposed method by comparing the extracted blood vessels with the ground truth vessels labeled by a dermatologist and show that the proposed method works equally well for FF-OCT volumes of different quality. The average F-measure improvements over the correlation-mapping OCT method, the modified amplitude-decorrelation OCT angiography method, and the RPCA method, respectively, are 0.1835, 0.1032, and 0.0458.

The dermal arteries in the cutaneous angiosome of the descending genicular artery

Studies examining thick skin of the thumb pad have challenged the existence of an arterial plexus in the papillary dermis. Instead of a plexus, discrete arterial units, interconnected by arterio-arterial anastomoses, were identified. We hypothesise that the dermal arteries of thin skin are arranged likewise and that there are fewer arterio-arterial anastomoses in the centre of an angiosome than in zones where neighbouring angiosomes overlap. To test these hypotheses, we examined the dermal arteries in the centre of the cutaneous angiosome of the descending genicular artery (DGA) and its zone of overlap with neighbouring angiosomes. Using traditional perfusion techniques, the cutaneous angiosomes of the DGA and the popliteal artery were identified in 11 fresh frozen human lower limbs. Biopsies were harvested from the centre of the cutaneous DGA angiosome and from the zone where neighbouring vascular territories overlapped. Employing high-resolution episcopic microscopy (HREM), digital volume data were generated and the dermal arteries were three-dimensionally reconstructed and examined. In all examined skin areas, the dermal arteries showed tree-like ramifications. The branches of the dermal arteries were connected on average by 1.73 ± 1.01 arterio-arterial anastomoses in the centre of the DGA angiosome and by 3.27 ± 1.27 in the zone where angiosomes overlapped. We demonstrate that discrete but overlapping dermal arterial units with a mean dimension of 1.62 ± 1.34 and 1.80 ± 1.56 mm² , respectively, supply oxygen and nutrients to the superficial dermis and epidermis of the thin skin of the medial femur. This forms the basis for diagnosing and researching skin pathologies.

Ex Vivo Confocal Fluorescence Microscopy for Rapid Evaluation of Tissues in Surgical Pathology Practice

CONTEXT

- Optical imaging techniques are currently available for imaging tissues without the need for any type of extensive tissue preparation. There are several applications for their potential use in surgical pathology practice.

OBJECTIVE

- To evaluate the feasibility of using a confocal fluorescence microscopy (CFM) platform for ex vivo examination of tissues obtained from surgical resections of breast, lung, kidney, and liver.

DESIGN

- Tissue fragments (0.5-1.0 cm) were immersed in 0.6 mM acridine orange for 6 seconds and imaged using a CFM platform at a 488-nm wavelength. The imaged tissues were subsequently fixed in formalin and processed routinely to generate hematoxylin-eosin-stained tissue sections. Mosaics of the grayscale CFM images were studied at different magnifications for recognition of the tissue and were compared with conventional histopathologic examination of hematoxylin-eosin tissue sections.

RESULTS

- We imaged 55 tissue fragments obtained from 16 breast (29%), 18 lung (33%), 14 kidney (25%), and 7 liver (13%) surgical excision specimens. Acridine orange labeled the nuclei, creating the contrast between nucleus and cytoplasm and thereby recapitulating the tissue architecture. We could obtain CFM images of good quality within 5 to 10 minutes that allowed recognition of the cytomorphologic details for categorization of the imaged tissue and were similar to histologic examination of hematoxylin-eosin tissue sections.

CONCLUSIONS

- The ease and speed of acquisition of CFM images together with the resolution and resemblance of the CFM images to hematoxylin-eosin sections suggest that the CFM platform has excellent potential for use in surgical pathology practice.

Improving lateral resolution and image quality of optical coherence tomography by the multi-frame superresolution technique for 3D tissue imaging

The multi-frame superresolution technique is introduced to significantly improve the lateral resolution and image quality of spectral domain optical coherence tomography (SD-OCT). Using several sets of low resolution C-scan 3D images with lateral sub-spot-spacing shifts on different sets, the multi-frame superresolution processing of these sets at each depth layer reconstructs a higher resolution and quality lateral image. Layer by layer processing yields an overall high lateral resolution and quality 3D image. In theory, the superresolution processing including deconvolution can solve the diffraction limit, lateral scan density and background noise problems together. In experiment, the improved lateral resolution by ~3 times reaching 7.81 µm and 2.19 µm using sample arm optics of 0.015 and 0.05 numerical aperture respectively as well as doubling the image quality has been confirmed by imaging a known resolution test target. Improved lateral resolution on in vitro skin C-scan images has been demonstrated. For in vivo 3D SD-OCT imaging of human skin, fingerprint and retina layer, we used the multi-modal volume registration method to effectively estimate the lateral image shifts among different C-scans due to random minor unintended live body motion. Further processing of these images generated high lateral resolution 3D images as well as high quality B-scan images of these in vivo tissues.

Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications

OCT has revolutionized the practice of ophthalmology over the past 10-20 years. Advances in OCT technology have allowed for the creation of novel OCT-based methods. OCT-Angiography (OCTA) is one such method that has rapidly gained clinical acceptance since it was approved by the FDA in late 2016. OCTA images are based on the variable backscattering of light from the vascular and neurosensory tissue in the retina. Since the intensity and phase of backscattered light from retinal tissue varies based on the intrinsic movement of the tissue (e.g. red blood cells are moving, but neurosensory tissue is static), OCTA images are essentially motion-contrast images. This motion-contrast imaging provides reliable, high resolution, and non-invasive images of the retinal vasculature in an efficient manner. In many cases, these images are approaching histology level resolution. This unprecedented resolution coupled with the simple, fast and non-invasive imaging platform have allowed a host of basic and clinical research applications. OCTA demonstrates many important clinical findings including areas of macular telangiectasia, impaired perfusion, microaneurysms, capillary remodeling, some types of intraretinal fluid, and neovascularization among many others. More importantly, OCTA provides depth-resolved information that has never before been available. Correspondingly, OCTA has been used to evaluate a spectrum of retinal vascular diseases including diabetic retinopathy (DR), retinal venous occlusion (RVO), uveitis, retinal arterial occlusion, and age-related macular degeneration among others. In this review, we will discuss the methods used to create OCTA images, the practical applications of OCTA in light of invasive dye-imaging studies (e.g. fluorescein angiography) and review clinical studies demonstrating the utility of OCTA for research and clinical practice.

Focus defect and dispersion mismatch in full-field optical coherence microscopy

Full-field optical coherence microscopy (FFOCM) is an optical technique, based on low-coherence interference microscopy, for tomographic imaging of semi-transparent samples with micrometer-scale spatial resolution. The differences in refractive index between the sample and the immersion medium of the microscope objectives may degrade the FFOCM image quality because of focus defect and optical dispersion mismatch. These phenomena and their consequences are discussed in this theoretical paper. Experimental methods that have been implemented in FFOCM to minimize the adverse effects of these phenomena are summarized and compared.

Optical coherence tomography based angiography [Invited]

Optical coherence tomography (OCT)-based angiography (OCTA) provides in vivo, three-dimensional vascular information by the use of flowing red blood cells as intrinsic contrast agents, enabling the visualization of functional vessel networks within microcirculatory tissue beds non-invasively, without a need of dye injection. Because of these attributes, OCTA has been rapidly translated to clinical ophthalmology within a short period of time in the development. Various OCTA algorithms have been developed to detect the functional micro-vasculatures in vivo by utilizing different components of OCT signals, including phase-signal-based OCTA, intensity-signal-based OCTA and complex-signal-based OCTA. All these algorithms have shown, in one way or another, their clinical values in revealing micro-vasculatures in biological tissues in vivo, identifying abnormal vascular networks or vessel impairment zones in retinal and skin pathologies, detecting vessel patterns and angiogenesis in eyes with age-related macular degeneration and in skin and brain with tumors, and monitoring responses to hypoxia in the brain tissue. The purpose of this paper is to provide a technical oriented overview of the OCTA developments and their potential pre-clinical and clinical applications, and to shed some lights on its future perspectives. Because of its clinical translation to ophthalmology, this review intentionally places a slightly more weight on ophthalmic OCT angiography.

Classification and analysis of human ovarian tissue using full field optical coherence tomography

In this study, a full field optical coherence tomography (FFOCT) system was used to analyze and classify normal and malignant human ovarian tissue. 14 ovarian tissue samples (7 normal, 7 malignant) were imaged with the FFOCT system and five features were extracted by analyzing the normalized image histogram from 56 FFOCT images, based on the differences in the morphology of the normal and malignant tissue samples. A generalized linear model (GLM) classifier was trained using 36 images, and sensitivity of 95.3% and specificity of 91.1% was obtained. 20 images were used to test the model, and a sensitivity of 91.6% and specificity of 87.7% was obtained.

Methods of Melanoma Detection

Detection and removal of melanoma, before it has metastasized, dramatically improves prognosis and survival. The purpose of this chapter is to (1) summarize current methods of melanoma detection and (2) review state-of-the-art detection methods and technologies that have the potential to reduce melanoma mortality. Current strategies for the detection of melanoma range from population-based educational campaigns and screening to the use of algorithm-driven imaging technologies and performance of assays that identify markers of transformation. This chapter will begin by describing state-of-the-art methods for educating and increasing awareness of at-risk individuals and for performing comprehensive screening examinations. Standard and advanced photographic methods designed to improve reliability and reproducibility of the clinical examination will also be reviewed. Devices that magnify and/or enhance malignant features of individual melanocytic lesions (and algorithms that are available to interpret the results obtained from these devices) will be compared and contrasted. In vivo confocal microscopy and other cellular-level in vivo technologies will be compared to traditional tissue biopsy, and the role of a noninvasive "optical biopsy" in the clinical setting will be discussed. Finally, cellular and molecular methods that have been applied to the diagnosis of melanoma, such as comparative genomic hybridization (CGH), fluorescent in situ hybridization (FISH), and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), will be discussed.

Fabrication and characterization of electrospinning/3D printing bone tissue engineering scaffold

A composite scaffold was fabricated with a method involving both electrospinning and 3D printing to give microscale pores and good mechanical properties. Biocompatibility and cell infiltration on the scaffold was evaluated by an in vitro study.

Optical Coherence Tomography Imaging of Normal, Chronologically Aged, Photoaged and Photodamaged Skin: A Systematic Review

BACKGROUND

Optical coherence tomography (OCT) is capable of providing a noninvasive real-time cross-sectional image of the skin through light-based interferometry, a method sometimes described as "light-based ultrasound." One key application of OCT in dermatology is the visualization of dermal collagen during chronological aging, photoaging, or photodamage. These skin conditions are typically managed by the practitioner's subjective assessment of severity and response to therapy.

OBJECTIVE

The purpose of this review is to present available evidence on the ability of OCT to image normal, chronologically aged, photoaged and photodamaged skin in human subjects.

METHODS AND MATERIALS

The authors have searched Medline, PubMed, EMBASE, Web of Science, Google Scholar, and Cochrane Library databases for published literature on the imaging of skin collagen by OCT using the following search terms: "optical coherence tomography," "OCT," "skin," "collagen," "photoaging," "wrinkles," and "photodamage."

RESULTS

The search resulted in 23 articles investigating OCT-based skin collagen imaging, which met their search criteria.

CONCLUSION

The authors anticipate tremendous growth in the field of OCT-based skin imaging that will parallel the development ultrasound technology has experienced over the past 30 years. They foresee that the use of OCT imaging to evaluate skin aging will not only help identify pathological changes earlier, but will also assist in the evaluation of the response to therapy longitudinally without biopsy.

Fingerprint imaging from the inside of a finger with full-field optical coherence tomography

Imaging below fingertip surface might be a useful alternative to the traditional fingerprint sensing since the internal finger features are more reliable than the external ones. One of the most promising subsurface imaging technique is optical coherence tomography (OCT), which, however, has to acquire 3-D data even when a single en face image is required. This makes OCT inherently slow for en face imaging and produce unnecessary large data sets. Here we demonstrate that full-field optical coherence tomography (FF-OCT) can be used to produce en face images of sweat pores and internal fingerprints, which can be used for the identification purposes.

Dark-field full-field optical coherence tomography

Full-field optical coherence tomography (FF-OCT) provides en face images from deep in the tissue with high spatial resolution. Specular reflections, however, may reduce image contrast as it can be much stronger than the backscattered signal from a specimen. To this end, we demonstrate dark-field FF-OCT (d-FF-OCT) that can block specular reflections by the help of an opaque disk in the pupil-conjugated plane. The reference mirror is replaced by a blazed grating, which eliminates a walk-off between the sample and the reference beams on a camera that otherwise limits the imaging field-of-view (FOV). We show that d-FF-OCT can suppress specular reflections efficiently from the glass-specimen interface by at least two orders of magnitude and yield higher contrast images compared to the conventional FF-OCT.

Recent advances in clinical application of optical coherence tomography of human skin

Optical coherence tomography (OCT) is an emerging noninvasive imaging method that uses infrared light and interferometric techniques. The method has become increasingly popular in skin research as well as daily dermatology practice. In the present brief review, we focused on recent (2009-2014) OCT studies on the human skin, which included a reasonable sample size and statistics. Twenty-five papers were selected and briefly described OCT of epidermal thickness, skin appendages, wound healing, extracellular matrix and skin fibrosis, vascular malformations, and skin tumors such as basal cell carcinoma, actinic keratoses, and malignant melanoma.

Assessment of Sentinel Node Biopsies With Full-Field Optical Coherence Tomography

Current techniques for the intraoperative analysis of sentinel lymph nodes during breast cancer surgery present drawbacks such as time and tissue consumption. Full-field optical coherence tomography is a novel noninvasive, high-resolution, fast imaging technique. This study investigated the use of full-field optical coherence tomography as an alternative technique for the intraoperative analysis of sentinel lymph nodes. Seventy-one axillary lymph nodes from 38 patients at Tenon Hospital were imaged minutes after excision with full-field optical coherence tomography in the pathology laboratory, before being handled for histological analysis. A pathologist performed a blind diagnosis (benign/malignant), based on the full-field optical coherence tomography images alone, which resulted in a sensitivity of 92% and a specificity of 83% (n = 65 samples). Regular feedback was given during the blind diagnosis, with thorough analysis of the images, such that features of normal and suspect nodes were identified in the images and compared with histology. A nonmedically trained imaging expert also performed a blind diagnosis aided by the reading criteria defined by the pathologist, which resulted in 85% sensitivity and 90% specificity (n = 71 samples). The number of false positives of the pathologist was reduced by 3 in a second blind reading a few months later. These results indicate that following adequate training, full-field optical coherence tomography can be an effective noninvasive diagnostic tool for extemporaneous sentinel node biopsy qualification.

A feasibility study of full-field optical coherence tomography for rapid evaluation of EUS-guided microbiopsy specimens

BACKGROUND

Rapid on-site evaluation of cytologic specimens is a way of determining the adequacy of fine-needle aspiration (FNA). However, alternatives may be useful when the presence of a cytotechnologist and/or pathologist is not possible.

OBJECTIVE

To evaluate the feasibility of using full-field optical coherence tomography (FFOCT) for FNA specimen quality assessment.

DESIGN

FFOCT images were acquired on gastric, pancreatic, pelvic, and lymph-node formalin-fixed FNA specimens and were compared with histology of the same samples.

SETTING

Pathology suite in a hospital.

PATIENTS

Fourteen patients undergoing gastric, pancreatic, pelvic, or lymph-node EUS-guided FNA biopsy.

INTERVENTIONS

FFOCT imaging on formalin-fixed samples before histologic procedures.

MAIN OUTCOME MEASUREMENTS

FFOCT imaging feasibility and visibility of normal and abnormal features on images.

RESULTS

FFOCT imaging was possible. Blood, mucus, muscle, collagen, and digestive mucosa could be identified as well as abnormal architectural features including infiltrative pancreatic ductal carcinoma and a neuroendocrine neoplasm. Lesions at the individual cell level could not be detected.

LIMITATIONS

The study was performed on a limited number of cases.

CONCLUSION

FFOCT offers rapid, noninvasive, nondestructive imaging of FNA biopsy specimens. In the future, it could be performed in the endoscopy suite to improve detection of satisfactory specimens and obviate the need for rapid on-site evaluation.

High-resolution episcopic microscopy (HREM): a tool for visualizing skin biopsies

We evaluate the usefulness of digital volume data produced with the high-resolution episcopic microscopy (HREM) method for visualizing the three-dimensional (3D) arrangement of components of human skin, and present protocols designed for processing skin biopsies for HREM data generation. A total of 328 biopsies collected from normally appearing skin and from a melanocytic nevus were processed. Cuboidal data volumes with side lengths of ~2×3×6 mm3 and voxel sizes of 1.07×1.07×1.5 µm3 were produced. HREM data fit ideally for visualizing the epidermis at large, and for producing highly detailed volume and surface-rendered 3D representations of the dermal and hypodermal components at a structural level. The architecture of the collagen fiber bundles and the spatial distribution of nevus cells can be easily visualized with volume-rendering algorithms. We conclude that HREM has great potential to serve as a routine tool for researching and diagnosing skin pathologies.

Optical coherence tomography in the diagnosis of basal cell carcinoma

Since its introduction in dermatology in the late 1990s optical coherence tomography (OCT) has been used to study many skin diseases, in particular non-melanoma skin cancer and it s precursors. Special attention has been paid to superficial basal cell carcinoma (BCC), and a number of smaller observational studies have been published. The diagnostic criteria for BCC of these studies are systematically reviewed. A systemic review of English language studies was performed using PubMed, Google Scholar and Royal Danish Library, to search for primary papers on OCT and BCC. The references of retrieved papers were searched by hand for further relevant papers. A total of 39 papers were identified (search date: 2014-01-15). 22 were excluded because they did not meet the inclusion criteria, leaving 17 papers for analysis. In 100% of the studies, rounded dark structures in the upper dermis surrounded by a hyperreflective halo possibly surrounded by a hyporeflective border and disruption of epidermal layering were described. In 53% of the reports a hyporeflective lateral tumour border was described. A range of other features were mentioned in a minority of the studies. It is suggested that these diagnostic criteria could be characteristic for identifying BCC lesions using OCT.

In vivo volumetric photoacoustic molecular angiography and therapeutic monitoring with targeted plasmonic nanostars

Photoacoustic (PA) imaging promises deeper tissue penetration while maintaining rich optical contrast as compared to other high resolution optical imaging techniques. In this report, a near-infrared pulse laser serves as the excitation source, and 128 ultrasonic transducers are spirally distributed on a hemispherical surface to receive PA signals for three-dimensional (3D) image reconstruction. With these attributes, the unique modality produces an isotropic and homogeneous spatial resolution (∼200 μm) with penetration depth of centimeters. Cyclic Arg-Gly-Asp (RGD) peptides conjugated plasmonic gold nanostars (RGD-GNS) are designed to specifically target over-expressed integrin α(v)β₃ on tumor neovasculature, enabling highly sensitive angiography and photothermal therapy (PTT). After the administration of RGD-GNS, tumor angiogenesis is clearly imaged with enhanced contrast, and the growth of tumor is effectively inhibited by PTT after laser irradiation. This study suggest that the PA angiography with plasmonic RGD-GNS can be applied as a triple functional platform for tumor diagnosis, PTT, and treatment monitoring. This PA technique offers deeper imaging depth with homogeneous resolution over existing optical imaging techniques for early diagnosis of tumor angiogenesis as well as on-the-spot nanotherapeutic evaluation.

[Differential diagnosis between keloid and hypertrophic scars: a new approach by full-field optical coherence tomography]

OBJECTIVE

To evaluate the efficacy of full-field optical coherence tomography to differentiate hypertrophic and keloid scars on ex-vivo tissues.

PATIENTS AND METHODS

All patients who underwent resection of pathological scar from November 2012 to September 2013 were analyzed. The scars were fixed in formalin and analyzed by conventional histology and full-field optical coherence tomography. The criteria for evaluation were: presence of dermal nodules, presence of cells and hyalinization of collagen.

RESULTS

Nineteen pathological scars were analyzed. Histology found 7 keloid scars, 7 mixed and 3 hypertrophic scars. The sensitivity of optical coherence tomography for the detection of dermal nodules was 100%. This technology was not helpful for detection of cells and hyalinized collagen.

CONCLUSION

In the present state of technology, optical coherence tomography did not identify the presence of cells, which makes the differential diagnosis difficult in the case of hypertrophic and keloid scars.