Optical coherence tomography for imaging of skin and skin diseases

Structural and functional imaging of psoriasis for severity assessment and quantitative monitoring of treatment response using high-resolution optoacoustic imaging

Psoriasis is a chronic inflammatory skin disease, characterized by thick scaly plaques. It imposes a notable disease burden with varying levels of severity affecting the quality of life significantly. Current disease severity assessment relies on semi-objective visual inspection based on the Psoriasis Area and Severity index (PASI) score that might not be sensitive to sub-clinical changes. Histology of psoriasis skin lesions necessitate invasive skin biopsies. This indicates an unmet need for a non-invasive, objective and quantitative approach to assess disease severity serially. Herein, we employ multispectral Raster-Scanning Optoacoustic Mesoscopy (ms-RSOM) derived structural and microvascular functional imaging metrics to examine the lesional and non-lesional skin in psoriasis subjects across different severities and also evaluate the treatment outcome in a subject with topical steroids and biologics, such as adalimumab. ms-RSOM derived structural metrics like epidermal thickness and total blood volume (TBV) and microvascular functional information such as oxygen saturation (sO2) are evaluated by spectrally resolving the endogenous chromophores like melanin, oxy-, and deoxy-hemoglobin. Initial findings reveal an elevated sO2 and TBV with severity in lesional and non-lesional psoriasis skin, thus representing increasing inflammation. An increase in epidermal thickness is also noted with the degree of severity, corresponding to the inflammation and increased abnormal cell growth. As a marker to evaluate the treatment response, we observed a decrease in epidermal thickness, sO2, and TBV in a psoriasis patient post-treatment, which is consistent with the decrease in the PASI score from 4.1 to 1.9. We envision that ms-RSOM has a huge potential to be translated into routine clinical setting for the diagnosis of severity and assessment of treatment monitoring in psoriasis subjects.

Non-invasive biochemical analysis and comparison of atopic dermatitis and psoriasis skin using handheld confocal Raman spectroscopy

A handheld non-invasive confocal Raman system (CRS) was used to evaluate the differences in skin biochemicals between atopic dermatitis (AD) and psoriasis, which are inflammatory skin conditions. Raman spectral measurements in the fingerprint and high wavenumber region were acquired using a portable in-house CRS system with excitation lasers operating at 671 and 785 nm. It was deduced that relative amount of water decreases in the following sequence of skin: healthy, psoriasis and AD. Moreover, differential trends were observed for the subclasses of ceramides such that ceramide 3 is lower in the lesional AD and psoriasis skin as compared to healthy, while ceramide 2 showed a contrasting trend of decrease in lesional AD and increase in lesional psoriasis as opposed to healthy skin. Amount of cholesterol was significantly higher in lesional psoriasis as compared to lesional AD and healthy skin. These differences can aid in an objective classification of the skin conditions and in the formulation of new disease-specific topical treatments.

How efficient is laser therapy for telangiectasias, spider veins, and cherry angiomas?-A study using dynamic optical coherence tomography

OBJECTIVES

A clinical study to investigate the effectiveness of pulsed dye laser (PDL) versus Nd:YAG laser in the treatment of telangiectasias, spider veins and cherry angiomas. Dynamic optical coherence tomography (D-OCT) was introduced as an innovative follow-up tool for evaluation of blood flow within superficial vessels and to allow visualization of morphological changes of the vasculature in vivo. The final aim of this study was to demonstrate a possible treatment benefit comparing both laser types.

MATERIALS AND METHODS

Vessel structures of 102 skin lesions were documented photographically and dermoscopically. Subsequently, lesions were imaged using optical coherence tomography before laser therapy (a), directly after the treatment (p) and after a follow-up 4-6 weeks after laser treatment. All lesions were treated using either a 595 nm PDL or a 1064 nm Nd:YAG laser. Two main vessel parameters, namely density and diameter, and their possible changes during follow-up were observed in 150/300/500 µm penetration depth using D-OCT and were subsequently compared between both treatment groups. Other analyzed vessel parameters were depth of the plexus, mean diameter, mean density, top edge of the vessel, columns, and spikes.

RESULTS

Both laser types are suitable options for the treatment of vascular skin lesions, with the most significant effect on cherry angiomas. PDL shows better results treating smaller vessels in upper skin regions, in comparison to Nd:YAG laser, achieving better results on deeper vessels, like spider veins. Using the applied laser settings, there was no statistically significant effect on telangiectasias.

CONCLUSION

D-OCT represents a new, noninvasive imaging method to evaluate blood flow and vessel morphology in the follow-up of telangiectasias, spider veins, and cherry angiomas, which underwent laser therapy.

Skin model for improving the reliability of the modified Rodnan skin score for systemic sclerosis

BACKGROUND

The gold standard for skin thickness assessment in systemic sclerosis (SSc) is the modified Rodnan skin score (mRSS); however, inter- and intra-rater variation can arise due to subjective methods and inexperience. The study aimed to determine the inter- and intra-rater variability of mRSS assessment using a skin model.

METHODS

A comparative study was conducted between January and December 2020 at Srinagarind Hospital, Khon Kaen University, Thailand. Thirty-six skin sites of 8 SSc patients underwent mRSS assessment: 4 times the first day and 1 time over the next 4 weeks by the same 10 raters. No skin model for mRSS assessment was used for the first two assessments, while one was used for the remaining three rounds of assessments. The Latin square design and Kappa statistic were used to determine inter- and intra-rater variability.

RESULTS

The kappa agreement for inter-rater variability improved when the skin model was used (from 0.4 to 0.5; 25%). The improvement in inter-rater variability was seen in the non-expert group, for which the kappa agreement rose from 0.3 to 0.5 (a change of 66.7%). Intra-rater variability did not change (kappa remained at 0.9), and the long-term effect of using a skin model slightly decreased by week 4 (Δkappa 0.9-0.7).

CONCLUSIONS

Using a skin model could be used to improve inter-rater variation in mRSS assessment, especially in the non-expert group. The model should be considered a reference for mRSS assessment in clinical practice and health education.

Non-destructive morphological observation of anatomical growth process in Haemaphysalis Longicornis tick specimens using optical coherence tomography

BACKGROUND:

Ticks are known as the representatives of hematophagous arachnids. They cause various tick-borne diseases, such as severe fever with thrombocytopenia syndrome (SFTS) and Lyme disease. To understand the mechanism of virus infection caused by ticks, morphology for the anatomical characteristics of crucial organs has been widely studied in acarological fields. The conventional methods used for tick observation have inevitable limitations. Dissection is the standard method to obtain the morphological information, and complex microscopy methods were utilized alternatively.

OBJECTIVE:

The study goal is to obtain the morphological information of ticks in different growth stages non-invasively.

METHODS:

Optical coherence tomography (OCT) is employed to acquire structural images of various internal organs without damage for observing the growth process of larva, nymph, and adult in Haemaphysalis longicornis ticks in real-time.

RESULTS:

Various internal organs, such as salivary glands, rectal sac, genital aperture, and anus, were well-visualized by the OCT enface and cross-sectional images, and the variation in size of these organs in each growth stage was compared quantitatively.

CONCLUSIONS:

Based on the obtained results, we confirmed the potential feasibility of OCT as a non-destructive real-time tool for morphological studies in acarology. Further research using OCT for acarological applications can include monitoring the growth process of ticks in terms of structural changes and investigating morphological differences between normal and virus-infected tick specimens.

Optical Technologies for the Improvement of Skin Cancer Diagnosis: A Review

The worldwide incidence of skin cancer has risen rapidly in the last decades, becoming one in three cancers nowadays. Currently, a person has a 4% chance of developing melanoma, the most aggressive form of skin cancer, which causes the greatest number of deaths. In the context of increasing incidence and mortality, skin cancer bears a heavy health and economic burden. Nevertheless, the 5-year survival rate for people with skin cancer significantly improves if the disease is detected and treated early. Accordingly, large research efforts have been devoted to achieve early detection and better understanding of the disease, with the aim of reversing the progressive trend of rising incidence and mortality, especially regarding melanoma. This paper reviews a variety of the optical modalities that have been used in the last years in order to improve non-invasive diagnosis of skin cancer, including confocal microscopy, multispectral imaging, three-dimensional topography, optical coherence tomography, polarimetry, self-mixing interferometry, and machine learning algorithms. The basics of each of these technologies together with the most relevant achievements obtained are described, as well as some of the obstacles still to be resolved and milestones to be met.

Role of skin tissue layers and ultra-structure in transcutaneous electrical stimulation including tDCS

BACKGROUND

During transcranial electrical stimulation (tES), including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), current density concentration around the electrode edges that is predicted by simplistic skin models does not match experimental observations of erythema, heating, or other adverse events. We hypothesized that enhancing models to include skin anatomical details, would alter predicted current patterns to align with experimental observations.

METHOD

We develop a high-resolution multi-layer skin model (epidermis, dermis, and fat), with or without additional ultra-structures (hair follicles, sweat glands, and blood vessels). Current flow patterns across each layer and within ultra-structures were predicted using finite element methods considering a broad range of modeled tissue parameters including 78 combinations of skin layer conductivities (S m^-1): epidermis (standard: 1.05 × 10^-5; range: 1.05 × 10^-6 to 0.465); dermis (standard: 0.23; range: 0.0023 to 23), fat (standard: 2 × 10^-4; range: 0.02 to 2 × 10^-5). The impact of each ultra-structures in isolation and combination was evaluated with varied basic geometries. An integrated final model is then developed.

RESULTS

Consistent with prior models, current flow through homogenous skin was annular (concentrated at the electrode edges). In multi-layer skin, reducing epidermis conductivity and/or increasing dermis conductivity decreased current near electrode edges, however no realistic tissue layer parameters produced non-annular current flow at both epidermis and dermis. Addition of just hair follicles, sweat glands, or blood vessels resulted in current peaks around each ultrastructure, irrespective of proximity to electrode edges. Addition of only sweat glands was the most effective approach in reducing overall current concentration near electrode edges. Representation of blood vessels resulted in a uniform current flow across the vascular network. Finally, we ran the first realistic model of current flow across the skin.

CONCLUSION

We confirm prior models exhibiting current concentration near hair follicles or sweat glands, but also exhibit that an overall annular pattern of current flow remains for realistic tissue parameters. We model skin blood vessels for the first time and show that this robustly distributes current across the vascular network, consistent with experimental erythema patterns. Only a state-of-the-art precise model of skin current flow predicts lack of current concentration near electrode edges across all skin layers.

Stimulation of collagen and elastin production in-vivo using 1,540 nm Er:Glass laser: assessment of safety and efficacy

Introduction: Induction of collagen and elastin remodeling in the human skin can be achieved by non-ablative fractional laser (NAFXL) and ablative fractional laser (AFXL). Our objective was to compare the safety, efficacy, tolerability, and ability to induce collagen and elastin remodeling of NAFXL versus AFXL in a series of treatments over time.Materials and Methods: In this prospective, proof of principle, single-case study, the safety, tolerability and efficacy of the laser systems were assessed via histopathology and clinical evaluations including photographs. Optical biopsies by means of multiphoton tomography (MPT) were used to evaluate the induction of collagen and elastin remodeling.Results: Treatments by both NAFXL and AFXL were well tolerated. The NAFXL system was found to be less painful and resulted in a shorter down- and healing times. MPT findings showed the superior capability of the AFXL procedure to induce collagen; on the other hand, elastin induction was more pronounced after NAFXL treatments.Conclusions: While NAFXL is as effective and safe as the traditional AFXL, it is better tolerated and has a shorter downtime. Serial optical biopsies over time over time can be a useful tool to assess the induction of collagen and elastin remodeling in the human skin.

Skin blood flow measurements during heat stress: technical and analytical considerations

During heat stress, the skin vasculature can greatly increase conductance secondary to vasodilation. The subsequent increase in skin blood flow allows for convective heat transfer from the core to the skin and between the skin surface and the surrounding environment. Measurement of skin blood flow, therefore, provides valuable information regarding heat exchange between the body and the environment. In addition, assessment of skin blood flow can be used to study vascular control mechanisms. Most often, skin blood flow is measured by venous occlusion plethysmography, Doppler ultrasound, laser-Doppler flowmetry, and, more recently, optical coherence tomography. However, important delimitations to each of these methods, which may be dependent on the research question, must be considered when responses from these approaches are interpreted. In this brief review, we discuss these methods of skin blood flow measurement and highlight potential sources of error and limitations. We also provide recommendations to guide the interpretation of skin blood flow data.

Morphological study of skin cancer lesions through a 3D scanner based on fringe projection and machine learning

The effective and non-invasive diagnosis of skin cancer is a hot topic, since biopsy is a costly and time-consuming surgical procedure. As skin relief is an important biophysical feature that can be difficult to perceive with the naked eye and by touch, we developed a novel 3D imaging scanner based on fringe projection to obtain morphological parameters of skin lesions related to perimeter, area and volume with micrometric precision. We measured 608 samples and significant morphological differences were found between melanomas and nevi (p<0.001). The capacity of the 3D scanner to distinguish these lesions was supported by a supervised machine learning algorithm resulting in 80.0% sensitivity and 76.7% specificity.

Potential of contrast agents to enhance in vivo confocal microscopy and optical coherence tomography in dermatology: A review

Distinction between normal skin and pathology can be a diagnostic challenge. This systematic review summarizes how various contrast agents, either topically delivered or injected into the skin, affect distinction between skin disease and normal skin when imaged by optical coherence tomography (OCT) and confocal microscopy (CM). A systematic review of in vivo OCT and CM studies using exogenous contrast agents on healthy human skin or skin disease was performed. In total, nine CM studies and one OCT study were eligible. Four contrast agents aluminum chloride (AlCl) n = 2, indocyanine green (ICG) n = 3, sodium fluorescein n = 3 and acetic acid n = 1 applied to CM in variety of skin diseases. ICG, acetic acid and AlCl showed promise to increase contrast of tumor nests in keratinocyte carcinomas. Fluorescein and ICG enhanced contrast of keratinocytes and adnexal structures. In OCT of healthy skin gold nanoshells, increased contrast of natural skin openings. Contrast agents may improve delineation and diagnosis of skin cancers; ICG, acetic acid and AlCl have potential in CM and gold nanoshells facilitate visualization of adnexal skin structures in OCT. However, as utility of bedside optical imaging increases, further studies with robust methodological quality are necessary to implement contrast agents into routine dermatological practice.

Non-invasive imaging in dermatology and the unique potential of raster-scan optoacoustic mesoscopy

In recent years, several non‐invasive imaging methods have been introduced to facilitate diagnostics and therapy monitoring in dermatology. The microscopic imaging methods are restricted in their penetration depth, while the mesoscopic methods probe deeper but provide only morphological, not functional, information. ‘Raster‐scan optoacoustic mesoscopy’ (RSOM), an emerging new imaging technique, combines deep penetration with contrast based on light absorption, which provides morphological, molecular and functional information. Here, we compare the capabilities and limitations of currently available dermatological imaging methods and highlight the principles and unique abilities of RSOM. We illustrate the clinical potential of RSOM, in particular for non‐invasive diagnosis and monitoring of inflammatory and oncological skin diseases.

Review of Modern Techniques for the Assessment of Skin Hydration

Skin hydration is a complex process that influences the physical and mechanical properties of skin. Various technologies have emerged over the years to assess this parameter, with the current standard being electrical probe-based instruments. Nevertheless, their inability to provide detailed information has prompted the use of sophisticated spectroscopic and imaging methodologies, which are capable of in-depth skin analysis that includes structural and composition details. Modern imaging and spectroscopic techniques have transformed skin research in the dermatological and cosmetics disciplines, and are now commonly employed in conjunction with traditional methods for comprehensive assessment of both healthy and pathological skin. This article reviews current techniques employed in measuring skin hydration, and gives an account on their principle of operation and applications in skin-related research.

Optical coherence tomography for diagnosing skin cancer in adults

BACKGROUND

Early accurate detection of all skin cancer types is essential to guide appropriate management and to improve morbidity and survival. Melanoma and squamous cell carcinoma (SCC) are high-risk skin cancers, which have the potential to metastasise and ultimately lead to death, whereas basal cell carcinoma (BCC) is usually localised, with potential to infiltrate and damage surrounding tissue. Anxiety around missing early cases needs to be balanced against inappropriate referral and unnecessary excision of benign lesions. Optical coherence tomography (OCT) is a microscopic imaging technique, which magnifies the surface of a skin lesion using near-infrared light. Used in conjunction with clinical or dermoscopic examination of suspected skin cancer, or both, OCT may offer additional diagnostic information compared to other technologies.

OBJECTIVES

To determine the diagnostic accuracy of OCT for the detection of cutaneous invasive melanoma and atypical intraepidermal melanocytic variants, basal cell carcinoma (BCC), or cutaneous squamous cell carcinoma (cSCC) in adults.

SEARCH METHODS

We undertook a comprehensive search of the following databases from inception up to August 2016: Cochrane Central Register of Controlled Trials; MEDLINE; Embase; CINAHL; CPCI; Zetoc; Science Citation Index; US National Institutes of Health Ongoing Trials Register; NIHR Clinical Research Network Portfolio Database; and the World Health Organization International Clinical Trials Registry Platform. We studied reference lists and published systematic review articles.

SELECTION CRITERIA

We included studies of any design evaluating OCT in adults with lesions suspicious for invasive melanoma and atypical intraepidermal melanocytic variants, BCC or cSCC, compared with a reference standard of histological confirmation or clinical follow-up.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data using a standardised data extraction and quality assessment form (based on QUADAS-2). Our unit of analysis was lesions. Where possible, we estimated summary sensitivities and specificities using the bivariate hierarchical model.

MAIN RESULTS

We included five studies with 529 cutaneous lesions (282 malignant lesions) providing nine datasets for OCT, two for visual inspection alone, and two for visual inspection plus dermoscopy. Studies were of moderate to unclear quality, using data-driven thresholds for test positivity and giving poor accounts of reference standard interpretation and blinding. Studies may not have been representative of populations eligible for OCT in practice, for example due to high disease prevalence in study populations, and may not have reflected how OCT is used in practice, for example by using previously acquired OCT images.It was not possible to make summary statements regarding accuracy of detection of melanoma or of cSCC because of the paucity of studies, small sample sizes, and for melanoma differences in the OCT technologies used (high-definition versus conventional resolution OCT), and differences in the degree of testing performed prior to OCT (i.e. visual inspection alone or visual inspection plus dermoscopy).Pooled data from two studies using conventional swept-source OCT alongside visual inspection and dermoscopy for the detection of BCC estimated the sensitivity of OCT as 95% (95% confidence interval (CI) 91% to 97%) and specificity of 77% (95% CI 69% to 83%).When applied to a hypothetical population of 1000 lesions at the mean observed BCC prevalence of 60%, OCT would miss 31 BCCs (91 fewer than would be missed by visual inspection alone and 53 fewer than would be missed by visual inspection plus dermoscopy), and OCT would lead to 93 false-positive results for BCC (a reduction in unnecessary excisions of 159 compared to using visual inspection alone and of 87 compared to visual inspection plus dermoscopy).

AUTHORS' CONCLUSIONS

Insufficient data are available on the use of OCT for the detection of melanoma or cSCC. Initial data suggest conventional OCT may have a role for the diagnosis of BCC in clinically challenging lesions, with our meta-analysis showing a higher sensitivity and higher specificity when compared to visual inspection plus dermoscopy. However, the small number of studies and varying methodological quality means implications to guide practice cannot currently be drawn.Appropriately designed prospective comparative studies are required, given the paucity of data comparing OCT with dermoscopy and other similar diagnostic aids such as reflectance confocal microscopy.

Novel application of anterior segment optical coherence tomography for periocular imaging

OBJECTIVE

This study aims to assess the use of optical coherence tomography (OCT) imaging for periocular skin lesions and to determine which characteristic features of these images can be correlated to histopathology.

DESIGN

This is an ongoing prospective study with Research Ethics Board approval.

PARTICIPANTS

Fifty patients over 18 years old with lesions clinically suspicious of nonmelanoma skin cancer on the periocular region were included in this study.

METHODS

After consent was obtained, clinical photographs and dermatoscopic images were obtained (DermLite II Hybrid M) from the lesion and its contralateral side. Subsequently, the patient was subjected to OCT imaging using the anterior segment module of a spectral domain OCT (Optovue Avanti) and images of the contralateral skin were also obtained. Surgical excision of the lesion was performed and sent for histopathological examination as per routine treatment. OCT images were then correlated to their matching digitalized histopathology section (Philips Ultra Fast Scanner 1.6 RA).

RESULTS

Based on the OCT images acquired from 50 patients, 8 predominant architectural features have been correlated to histopathology: hyperkeratosis, acanthosis, loss of dermal-epidermal junction delineation, hyporeflective tumour nests, cystic structures, "bunch of grapes" nodules, hyperreflective nests, and ulcerations. Results observed from 45 malignant lesions (basal cell carcinoma, squamous cell carcinoma, and sebaceous gland carcinoma) suggest that groups of features and their layout within the same OCT image may be associated to specific tumour characteristics.

CONCLUSIONS

Current data suggest that anterior-segment OCT imaging is a noninvasive imaging modality for periocular lesions and may be a valuable tool to help differentiate between some tumour types before a biopsy is performed.

Combination of structural and vascular optical coherence tomography for differentiating oral lesions of mice in different carcinogenesis stages

Differentiating between early malignancy and benign lesions in oral cavities is difficult using current optical tools. As has been shown in previous studies, microvascular changes in squamous epithelium can be regarded as a key marker for diagnosis. We propose the combination of structural and vascular optical coherence tomography (OCT) imaging for the investigation of disease related changes. Progressive thickness changes of epithelium and the destruction of underlying lamina propria was observed during cancer development in a 4- nitroquinoline-1-oxide (4NQO) mouse model. At the same time, microvascular changes in hyperplasia, dysplasia, carcinoma in situ and advanced cancer were observed. Findings from OCT imaging were compared with histology.

Magnetomotive Displacement of the Tympanic Membrane Using Magnetic Nanoparticles: Toward Enhancement of Sound Perception

OBJECTIVE

A novel hearing-aid scheme using magnetomotive nanoparticles (MNPs) as transducers in the tympanic membrane (TM) is proposed, aiming to noninvasively and directly induce a modulated vibration on the TM.

METHODS

In this feasibility study, iron oxide (Fe₃O₄) nanoparticles were applied on ex vivo rat TM tissues and allowed to diffuse over ∼2 h. Subsequently, magnetic force was exerted on the MNP-laden TM via a programmable electromagnetic solenoid to induce the magnetomotion. Optical coherence tomography (OCT), along with its phase-sensitive measurement capabilities, was utilized to visualize and quantify the nanometer-scale vibrations generated on the TM tissues.

RESULTS

The magnetomotive displacements induced on the TM were significantly greater than the baseline vibration of the TM without MNPs. In addition to a pure frequency tone, a chirped excitation and the corresponding spectroscopic response were also successfully generated and obtained. Finally, visualization of volumetric TM dynamics was achieved.

CONCLUSION

This study demonstrates the effectiveness of magnetically inducing vibrations on TMs containing iron oxide nanoparticles, manipulating the amplitude and the frequency of the induced TM motions, and the capability of assessing the magnetomotive dynamics via OCT.

SIGNIFICANCE

The results demonstrated here suggest the potential use of this noninvasive magnetomotive approach in future hearing aid applications. OCT can be utilized to investigate the magnetomotive dynamics of the TM, which may either enhance sound perception or magnetically induce the perception of sound without the need for acoustic speech signals.

In vivo automated quantification of thermally damaged human tissue using polarization sensitive optical coherence tomography

Over the decades numerous technologies have been performed for the quantification of skin injuries, but their poor sensitivity, specificity and accuracy limits their applications. Optical coherence tomography (OCT) can be potential tool for the identification but the modern high-speed OCT system acquires huge amount of data, which will be very time-consuming and tedious process for human interpretation. Our proposed method opens the possibility of fully automated quantitative analysis based on morphological features of thermally damaged tissue, which will become biomarker for the removal of non-viable skin. The proposed method is based on multi-level ensemble classifier by dissociating morphological features (A-line, B-scan, phase images) extracted from Polarization Sensitive Optical Coherence Tomography (PS-OCT) images. Our proposed classifier attained the average sensitivity, specificity and accuracy is 92.22%, 87.2% and 92.5%, respectively, in detecting the thermally damaged human skin. Moreover, we show that our classifier is one of the best possible classifier based on features extracted from PS-OCT images, which demonstrates the significance of PS-OCT data in detecting abnormality in human skin.

Optical coherence tomography in gynecology: a narrative review

Modern gynecologic practice requires noninvasive diagnostics techniques capable of detecting morphological and functional alterations in tissues of female reproductive organs. Optical coherence tomography (OCT) is a promising tool for providing imaging of biotissues with high resolution at depths up to 2 mm. Design of the customized probes provides wide opportunities for OCT use in gynecology. This paper contains a retrospective insight into the history of OCT employment in gynecology, an overview of the existing gynecologic OCT probes, including those for combination with other diagnostic modalities, and state-of-the-art application of OCT for diagnostics of tumor and nontumor pathologies of female genitalia. Perspectives of OCT both in diagnostics and treatment planning and monitoring in gynecology are overviewed.

Imaging Blood Vessel Morphology in Skin: Dynamic Optical Coherence Tomography as a Novel Potential Diagnostic Tool in Dermatology

Conventional optical coherence tomography (OCT) enables the visualization of morphological changes of skin cancer. The use of OCT in the diagnostic investigation and in the therapy decision of non-melanoma skin cancer and other skin changes is already established, and has found its way into routine practice. With the development of speckle-variance OCT, also named dynamic OCT (D-OCT), the vascular architecture and the blood flow of the skin can be displayed in vivo and in 3D. This novel angiographic variant of OCT offers the ability to visualize and measure vessel morphology providing a new insight into healthy, inflammatory and neoplastic skin lesions such as malignant melanoma. This review focuses on the possibilities of using D-OCT on healthy and diseased skin. We suggest and illustrate key diagnostic characteristics by analyzing the initial publications and preliminary unpublished data on vessel morphology and distribution. The potential of D-OCT as a diagnostic tool in dermatology is examined and may give rise to future studies on D-OCT, which are needed to confirm the aforementioned features.

Multimodal imaging for nonmelanoma skin cancer margin delineation

BACKGROUND AND OBJECTIVE

Nonmelanoma skin cancer (NMSC) is the most common form of cancer worldwide. The most effective form of treating this cancer is its surgical removal. As NMSC rarely metastasize, its complete excision is often curative. We investigated the potential of combining Terahertz Pulsed Imaging (TPI) with polarization enhanced reflectance optical imaging for the accurate intraoperative delineation of NMSC.

MATERIALS AND METHODS

Fresh thick samples with residual cancer were obtained from surgeries. The samples were imaged within two hours using polarization optical and TPI systems without remounting. Analysis of the TPI results was performed in the frequency domain. Co- and cross-polarized optical images were acquired at 410 nm. Superficial optical images were obtained by subtracting cross-polarized from the respective co-polarized images. Terahertz, optical, and histological images were overlaid and compared.

RESULTS AND CONCLUSIONS

Our results show that the frequency powers of diseased and normal skin tissues differ significantly at 0.47 THz. While TPI has demonstrated contrast between diseased and normal tissue, it can also highlight normal structures. As TPI alone lacks the resolution necessary to distinguish between tissue types morphologically, polarization optical imaging was used for the inspection of the suspicious areas highlighted by TPI. Combined TPI and optical imaging has the potential for quick intraoperative delineation of cancers. Lasers Surg. Med. 49:319-326, 2017. © 2016 Wiley Periodicals, Inc.

Microneedle characterisation: the need for universal acceptance criteria and GMP specifications when moving towards commercialisation

With interest in microneedles as a novel drug transdermal delivery system increasing rapidly since the late 1990s (Margetts and Sawyer Contin Educ Anaesthesia Crit Care Pain. 7(5):171-76, 2007), a diverse range of microneedle systems have been fabricated with varying designs and dimensions. However, there are still very few commercially available microneedle products. One major issue regarding microneedle manufacture on an industrial scale is the lack of specific quality standards for this novel dosage form in the context of Good Manufacturing Practice (GMP). A range of mechanical characterisation tests and microneedle insertion analysis techniques are used by researchers working on microneedle systems to assess the safety and performance profiles of their various designs. The lack of standardised tests and equipment used to demonstrate microneedle mechanical properties and insertion capability makes it difficult to directly compare the in use performance of candidate systems. This review highlights the mechanical tests and insertion analytical techniques used by various groups to characterise microneedles. This in turn exposes the urgent need for consistency across the range of microneedle systems in order to promote innovation and the successful commercialisation of microneedle products.

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.

Quantified ultrasound elastography in the assessment of cutaneous carcinoma

OBJECTIVE

To evaluate the feasibility of high-frequency ultrasound and ultrasound elastography (USE) in discriminating benign from malignant skin lesions in a prospective cohort study and to introduce the use of a "strain ratio" for evaluation of skin lesions.

METHODS

A commercial ultrasound system with a 14-MHz transducer was used to visualize skin lesions requiring biopsy on clinical evaluation. Anatomic ultrasound and USE imaging of the skin lesions was performed using 2- to 4-mm gel stand-off pads. A region of interest was manually selected over the area of each lesion with the lowest strain. The concept of a strain ratio of the compressibility of the normal skin at the corresponding layer to that of the least compressible region of a lesion in question was created and applied. This ratio was subsequently correlated with blind histopathological evaluation for malignancy.

RESULTS

55 patients were included in the study with a total of 67 lesions evaluated. 29 lesions were malignant and 38 benign. All malignant lesions had strain ratios ≥3.9. All benign lesions had strain ratios ≤3.0. A diagnostic value between 3.0 and 3.9 would result in 100% sensitivity and specificity in the characterization of these lesions as malignant.

CONCLUSION

This pilot study demonstrated that USE plus strain ratio appears to be a promising modality in providing diagnostic determination between cancerous and benign primary solitary skin lesions prior to biopsy.

ADVANCES IN KNOWLEDGE

This is the first reported study applying an original mathematical elastographic ratio, or strain ratio, to evaluate primary solitary skin lesions.

High-definition optical coherence tomography of melanocytic skin lesions

High-definition optical coherence tomography (HD-OCT) scanners have recently been developed. We assessed micromorphological HD-OCT correlates of benign naevi (BN) and malignant melanoma (MM). 28 BN and 20 MM were studied using HD-OCT and histology. Epidermal honeycomb/cobblestone pattern, regular junctional cell nests, and edged papillae are more often observed in BN, whereas fusion of rete ridges, pagetoid cells and junctional and/or dermal nests with atypical cells are more frequently seen in MM. A high overlap of HD-OCT features in BN and MM was observed and in 20% of MM we did not find evidence for malignancy in OCT images at all. Using HD-OCT it is possible to visualize architectural and cellular alterations of melanocytic skin lesions. The overlap of HD-OCT features seen in BN and MM and the absence of suspicious HD-OCT features in some MM represents an important limitation of HD-OCT affecting the sensitivity of HD-OCT in diagnosing MM. High-definition optical coherence tomography and the corresponding vertically sectioned histology of a compound naevus.

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.

High-definition optical coherence tomography intrinsic skin ageing assessment in women: a pilot study

Several non-invasive two-dimensional techniques with different lateral resolution and measurable depth range have proved to be useful in assessing and quantifying morphological changes in skin ageing. Among these, only in vivo microscopy techniques permit histometric measurements in vivo. Qualitative and quantitative assessment of chronological (intrinsic) age-related (IAR) morphological changes of epidermis, dermo-epidermal junction (DEJ), papillary dermis (PD), papillary-reticular dermis junction and reticular dermis (RD) have been performed by high-definition optical coherence tomography in real time 3-D. HD-OCT images were taken at the internal site of the right upper arm. Qualitative HD-OCT IAR descriptors were reported at skin surface, at epidermal layer, DEJ, PD and upper RD. Quantitative evaluation of age-related compaction and backscattered intensity or brightness of different skin layers was performed by using the plugin plot z-axis profile of ImageJ^® software permitting intensity assessment of HD-OCT (DICOM) images (3-D images). Analysis was in blind from all clinical information. Sixty, fair-skinned (Fitzpatrick types I–III) healthy females were analysed retrospectively in this study. The subjects belonged to three age groups: twenty in group I aged 20–39, twenty in group II aged 40–59 and twenty in group III aged 60–79. Only intrinsic ageing in women has been studied. Significant age-related qualitative and quantitative differences could be noticed. IAR changes in dermal matrix fibers morphology/organisation and in microvasculature were observed. The brightness and compaction of the different skin layers increased significantly with intrinsic skin ageing. The depth of visibility of fibers in RD increased significantly in the older age group. In conclusion, HD-OCT allows 3-D in vivo and real time qualitative and quantitative assessment of chronological (intrinsic) age-related morphological skin changes at high resolution from skin surface to a depth of the superficial reticular dermis.

Comparative analysis of combined spectral and optical tomography methods for detection of skin and lung cancers

Malignant skin tumors of different types were studied in vivo using optical coherence tomography (OCT), backscattering (BS), and Raman spectroscopy (RS). A multimodal method is proposed for early cancer detection based on complex analysis of OCT images by their relative alteration of scattered-radiation spectral intensities between malignant and healthy tissues. An increase in average accuracy of diagnosis was observed for a variety of cancer types (9% sensitivity, 8% specificity) by a multimodal RS-BS-OCT system in comparison with any of the three methods used separately. The proposed approach equalizes the processing rates for all methods and allows for simultaneous imaging and classification of tumors.

Optical coherence tomography microangiography for monitoring the response of vascular perfusion to external pressure on human skin tissue

Characterization of the relationship between external pressure and blood flow is important in the examination of pressure-induced disturbance in tissue microcirculation. Optical coherence tomography (OCT)-based microangiography is a promising imaging technique, capable of providing the noninvasive extraction of functional vessels within the skin tissue with capillary-scale resolution. Here, we present a feasibility study of OCT microangiography (OMAG) to evaluate changes in blood perfusion in response to externally applied pressure on human skin tissue in vivo. External force is loaded normal to the tissue surface at the nailfold region of a healthy human volunteer. An incremental force is applied step by step and then followed by an immediate release. Skin perfusion events including baseline are continuously imaged by OMAG, allowing for visualization and quantification of the capillary perfusion in the nailfold tissue. The tissue strain maps are simultaneously evaluated through the available OCT structural images to assess the relationship of the microcirculation response to the applied pressure. The results indicate that the perfusion progressively decreases with the constant increase of pressure. Reactive hyperemia occurs right after the removal of the pressure. The perfusion returns to the baseline level after a few minutes. These findings suggest that OMAG may have great potential for quantitatively assessing tissue microcirculation in the locally pressed tissue in vivo.

Hydrogel-forming microneedles increase in volume during swelling in skin, but skin barrier function recovery is unaffected

We describe, for the first time, quantification of in-skin swelling and fluid uptake by hydrogel-forming microneedle (MN) arrays and skin barrier recovery in human volunteers. Such MN arrays, prepared from aqueous blends of hydrolyzed poly(methylvinylether/maleic anhydride) (15%, w/w) and the cross-linker poly(ethyleneglycol) 10,000 Da (7.5%, w/w), were inserted into the skin of human volunteers (n = 15) to depths of approximately 300 μm by gentle hand pressure. The MN arrays swelled in skin, taking up skin interstitial fluid, such that their mass had increased by approximately 30% after 6 h in skin. Importantly, however, skin barrier function recovered within 24 h after MN removal, regardless of how long the MN had been in skin or how much their volume had increased with swelling. Further research on closure of MN-induced micropores is required because transepidermal water loss measurements suggested micropore closure, whereas optical coherence tomography indicated that MN-induced micropores had not closed over, even 24 h after MN had been removed. There were no complaints of skin reactions, adverse events, or strong views against MN use by any of the volunteers. Only some minor erythema was noted after patch removal, although this always resolved within 48 h, and no adverse events were present on follow-up.

Optical coherence tomography for presurgical margin assessment of non-melanoma skin cancer - a practical approach

In the clinical setting, optical coherence tomography (OCT) is applicable for the non-invasive diagnosis of skin cancer and may in particular be used for margin definition prior to excision. In this regard, OCT may improve the success rate of removing tumor lesions more effectively, preventing repetitive excision, which may subsequently result in smaller excisions. In this study, we have aimed to evaluate the applicability of OCT for in vivo presurgical margin assessment of non-melanocytic skin tumors (NMSC) and to describe the feasibility of different scanning techniques. A total number of 18 patients planned for excision of lesions suspicious of NMSC were included in this study. Based on OCT, we defined the specific tumor margins on 19 lesions preoperatively using different scanning modalities. Sixty-one margin points and five complete tumor margins were analysed on 18 patients with a total of 19 lesions including 63% basal cell carcinoma (BCC) (n = 12), 16% (n = 3) squamous cell carcinoma (SCC) and 21% of other types of skin tumors (n = 4) were classified. In 84% of the cases (n = 16), the OCT-defined lateral margins correctly indicated complete removal of the tumor. The surgical margins chosen by the surgeon never fell below the OCT-defined margin. Regarding the techniques of marginal definition, punctual tumor border scan in the perpendicular direction, with an extension of free-run scans for unsure cases can hardly be recommended. This study shows that suspected NMSC can effectively be confirmed, and furthermore, resection margin can be minimized under OCT control without reducing the rate of complete removal.

Microneedle-mediated intrascleral delivery of in situ forming thermoresponsive implants for sustained ocular drug delivery

OBJECTIVES

This paper describes use of minimally invasive hollow microneedle (HMN) to deliver in situ forming thermoresponsive poloxamer-based implants into the scleral tissue to provide sustained drug delivery.

METHODS

In situ forming poloxamer formulations were prepared and investigated for their rheological properties. HMN devices 400, 500 and 600 μm in height were fabricated from hypodermic needles (i.e. 27, 29 and 30 G) and tested for depth of penetration into rabbit sclera. Maximum force and work required to expel different volumes of poloxamer formulations was also investigated. Release of fluorescein sodium (FS) from intrasclerally injected implants was also investigated. Optical coherence tomography (OCT) was used to examine implant localisation and scleral pore-closure.

KEY FINDINGS

Poloxamer formulations showed Newtonian behaviour at 20°C and pseudoplastic (shear-thinning) behaviour at 37°C. Maximum force and work required to expel different volumes of poloxamer formulations with different needles ranged from 0.158 to 2.021 N and 0.173 to 6.000 N, respectively. OCT showed intrascleral localisation of implants and scleral pore-closure occurred within 2-3 h. Sustain release of FS was noticed over 24 h and varied with depth of implant delivery.

CONCLUSIONS

This study shows that the minimally invasive HMN device can localise in situ forming implants in the scleral tissue and provide sustained drug delivery.

Optical coherence tomography (OCT) of collagen in normal skin and skin fibrosis

Optical coherence tomography (OCT) is a non-invasive imaging modality that is transforming clinical diagnosis in dermatology and other medical fields. OCT provides a cross-sectional evaluation of the epidermis and dermis and allows in vivo imaging of skin collagen. Upregulated collagen content is a key feature of fibrotic skin diseases. These diseases are often managed by the practitioner's subjective assessment of disease severity and response to therapies. The purpose of this review is to provide an overview of the principles of OCT and present available evidence on the ability of OCT to image skin collagen in vivo for the diagnosis and management of diseases characterized by skin fibrosis. We review OCT studies that characterize the collagen content in normal skin and fibrotic skin diseases including systemic sclerosis and hypertrophic scars secondary to burn, trauma, and other injury. We also highlight several limitations of OCT and suggest enhancements to improve OCT imaging of skin fibrosis. We conclude that OCT imaging has the potential to serve as an objective, non-invasive measure of collagen's status and disease progression for use in both research trials and clinical practice. The future use of OCT imaging as a quantitative imaging biomarker of fibrosis will help identify fibrosis and facilitate clinical examination in monitoring response to treatment longitudinally without relying on serial biopsies. The use of OCT technology for quantification of fibrosis is in the formative stages and we foresee tremendous growth potential, similar to the ultrasound development paradigm that evolved over the past 30 years.

Evaluation of optical coherence tomography as a non-invasive diagnostic tool in cutaneous wound healing

BACKGROUND

The monitoring of wound-healing processes is indispensable for the therapeutic effectiveness and improved care of chronic wounds. Histological sections provide the best morphological assessment of wound recovery, but cause further tissue destruction and increase the risk of infection. Therefore, it is reasonable to apply a diagnostic tool that allows a non-invasive and reliable observation of morphological changes in wound healing.

METHODS

Optical coherence tomography (OCT) is an imaging technique for in vivo evaluation of skin diseases with a resolution close to histopathology. The aim of this study was to investigate whether OCT is suited to display the phases of wound healing. For this purpose, six patients with chronic wounds were objectively characterized by OCT during a period of 2 weeks.

RESULTS

Comparable results between histological findings and OCT were achieved. OCT allowed the detection of partial loss of the epidermis, vasoconstriction, vasodilatation and epithelialization.

CONCLUSION

Consequently, OCT could be a potential non-invasive diagnostic tool for the characterization and monitoring of cutaneous wound-healing processes over time.

Computational and experimental characterization of skin mechanics: identifying current challenges and future directions

The characterization of skin mechanics has many clinical implications and has been an active area of research for the past few decades. Biomechanical models have evolved from earlier empirical models to state-of-the-art structural models that provide linkage between tissue microstructure and macroscopic stress-strain response. To maximize the accuracy and predictive capabilities of such computational models, there is a need to reliably identify often a large number of unknown model parameters. This is critically dependent on the availability of experimental data that cover an extensive range of different deformation modes, and quantification of internal structural features, such as collagen orientation. To this end, future challenges should include the ongoing development of noninvasive instrumentation and imaging modalities for in vivo skin measurements. We highlight the important concept of tightly integrating computational models, instrumentation, and imaging modalities into a single platform to investigate skin biomechanics.

Optical coherence tomography: its role in daily dermatological practice

Optical coherence tomography (OCT) is a non-invasive, tomographic imaging technique which generates high-resolution in-vivo images up to mid-dermal layers. Due to continuous technological improvements, OCT is moving from research projects into daily dermatological practice. It can complement other imaging methods like high-frequency ultrasound or confocal microscopy. There is a wide variety of indications for OCT. In addition to aiding in the diagnosis and clinical monitoring of inflammatory dermatoses, OCT is a very useful and feasible technique in dermato-oncology.