In vivo confocal scanning laser microscopy in dermatology

Skin Cancer Pathobiology at a Glance: A Focus on Imaging Techniques and Their Potential for Improved Diagnosis and Surveillance in Clinical Cohorts

Early diagnosis is essential for completely eradicating skin cancer and maximizing patients' clinical benefits. Emerging optical imaging modalities such as reflectance confocal microscopy (RCM), optical coherence tomography (OCT), magnetic resonance imaging (MRI), near-infrared (NIR) bioimaging, positron emission tomography (PET), and their combinations provide non-invasive imaging data that may help in the early detection of cutaneous tumors and surgical planning. Hence, they seem appropriate for observing dynamic processes such as blood flow, immune cell activation, and tumor energy metabolism, which may be relevant for disease evolution. This review discusses the latest technological and methodological advances in imaging techniques that may be applied for skin cancer detection and monitoring. In the first instance, we will describe the principle and prospective clinical applications of the most commonly used imaging techniques, highlighting the challenges and opportunities of their implementation in the clinical setting. We will also highlight how imaging techniques may complement the molecular and histological approaches in sharpening the non-invasive skin characterization, laying the ground for more personalized approaches in skin cancer patients.

Recent advances in high-speed photoacoustic microscopy

Photoacoustic (PA) microscopy (PAM) has achieved remarkable progress in biomedicine in the past decade. It is a fast-rising imaging modality with diverse applications, such as hemodynamics, oncology, metabolism, and neuroimaging. Combining optical excitation and acoustic detection, the hybrid nature of PAM provides advantages of rich contrast and deep penetration. In recent years, high-speed PAM has flourished and enabled high-speed wide-field imaging of functional activity. In this review, we summarize the most recent advances in high-speed PAM technologies, including high-repetition-rate multi-wavelength laser development, fast scanning techniques, and novel PA signal acquisition strategies.

Morphological Analysis of Dermatoporosis by in vivo Reflectance Confocal Microscopy and Ultrasonography

Background

Dermatoporosis is defined as a chronic cutaneous fragility and insufficiency syndrome. It results from chronological aging, long-term and unprotected sun exposure, genetic factors, or the chronic use of topical and systemic corticosteroids. There is currently a lack of noninvasive tools for the evaluation and quantification of dermatoporosis.

Objectives

The aim of this study was to define the dermal-epidermal modifications which characterize dermatoporosis using noninvasive methods such as in vivo reflectance confocal microscopy (RCM) and ultrasound (US).

Subjects and Methods

Seventeen patients with stage I dermatoporosis and 14 healthy volunteers were included in the study. The posterior surface of the right forearm was analyzed in all subjects, and stellate pseudoscars and senile purpura in patients with dermatoporosis were analyzed when possible. We used a commercially available reflectance confocal microscope and measured different histometric parameters (thickness of the epidermis and its different layers, cellular architecture, aspect of the dermal-epidermal junction and the dermis). We also used a commercially available US skin system to define the dermal-epidermal thickness (DET) in all subjects.

Results

The DET measured with the US skin system was significantly different between the two groups: mean value 1.19 mm (volunteers group) versus 0.81 mm (patient group). The significant differences measured with RCM were (1) epidermal thickness, (2) number of dermal papillae, and (3) thickness of solar elastosis. Stellate pseudoscars are also characterized by a modified dermis, with a linear organization of the collagen bundles.

Conclusion

US and in vivo RCM are useful tools for the diagnosis of dermatoporosis. Dermal-epidermal atrophy, reduction of dermal papillae/area, and the thickness of dermal elastosis seem to be the major histometric parameters which characterize dermatoporosis.

Current and future applications of confocal laser scanning microscopy imaging in skin oncology

Confocal laser scanning microscopy (CLSM) is a modern imaging technique that enables the in vivo or ex vivo characterization of skin lesions located in the epidermis and superficial dermis with a high quasi-microscopic resolution. Currently, it is considered to be the most promising imaging tool for the evaluation of superficial skin tumors. The in vivo mode adds the advantage of noninvasive, dynamic, in real-time assessment of the tumor associated vasculature and inflammation. It offers the possibility to repeatedly examine the same skin area without causing any damage and to monitor disease progression and treatment outcome. Furthermore, this novel technology allows the evaluation of the entire lesion and can be used to guide biopsies and to define tumor margins before surgical excision or other invasive therapies. CLSM diagnostic features may differentiate between the various histologic subtypes of skin tumors and therefore helps in choosing the best therapeutic approach. In this study, we present the CLSM characteristic features of the most common melanocytic and non-melanocytic skin tumors, as well as future possible CLSM applications in the study of experimental skin tumorigenesis on animal models.

Preclinical quantitative in-vivo assessment of skin tissue vascularity in radiation-induced fibrosis with optical coherence tomography

Radiation therapy (RT) is widely and effectively used for cancer treatment but can also cause deleterious side effects, such as a late-toxicity complication called radiation-induced fibrosis (RIF). Accurate diagnosis of RIF requires analysis of histological sections to assess extracellular matrix infiltration. This is invasive, prone to sampling limitations, and thus rarely used; instead, current practice relies on subjective clinical surrogates, including visual observation, palpation, and patient symptomatology questionnaires. This preclinical study demonstrates that functional optical coherence tomography (OCT) is a useful tool for objective noninvasive in-vivo assessment and quantification of fibrosis-associated microvascular changes in tissue. Data were collected from murine hind limbs 6 months after 40-Gy single-dose irradiation and compared with nonirradiated contralateral tissues of the same animals. OCT-derived vascular density and average vessel diameter metrics were compared to quantitative vascular analysis of stained histological slides. Results indicate that RIF manifests significant microvascular changes at this time point posttreatment. Abnormal microvascular changes visualized by OCT in this preclinical setting suggest the potential of this label-free high-resolution noninvasive functional imaging methodology for RIF diagnosis and assessment in the context of clinical RT.

Analysis of debrided and non-debrided invasive squamous cell carcinoma skin lesions by in vivo reflectance confocal microscopy before and after therapy

Hyperkeratosis hinders the application of reflectance confocal microscopy (RCM) to image squamous cell carcinoma (SCC). Not all lesions with SCC show hyperkeratosis, and these lesions can be directly imaged. However, lesions with hyperkeratosis can be treated by debriding the hyperkeratotic surface for further imaging. RCM was used to investigate patients with suspected SCC. Lesions without obvious keratosis underwent direct RCM examinations. Lesions with obvious keratosis were treated by debriding the hyperkeratotic surface. The following main RCM criteria were used to diagnose invasive SCC: atypical keratinocytes arranged in nests, islands, and disarrangement patterns; an atypical honeycomb pattern; the absence of a cobblestone pattern; and non-edged dermal papillae. Other characteristics of invasive SCC observed by confocal microscopy included keratin pearl structures, hyperkeratosis, and inflammatory cell infiltration. During the follow-up period after treatment, both the cobblestone pattern and edged dermal papillae were as important as the typical honeycomb pattern in suggesting a normal skin structure. Our findings indicate RCM is a valuable tool to noninvasively examine the histology of invasive SCC before and after therapy.

Noninvasive, label-free, three-dimensional imaging of melanoma with confocal photothermal microscopy: Differentiate malignant melanoma from benign tumor tissue

Skin cancer is one of the most common cancers. Melanoma accounts for less than 2% of skin cancer cases but causes a large majority of skin cancer deaths. Early detection of malignant melanoma remains the key factor in saving lives. However, the melanoma diagnosis is still clinically challenging. Here, we developed a confocal photothermal microscope for noninvasive, label-free, three-dimensional imaging of melanoma. The axial resolution of confocal photothermal microscope is ~3 times higher than that of commonly used photothermal microscope. Three-dimensional microscopic distribution of melanin in pigmented lesions of mouse skin is obtained directly with this setup. Classic morphometric and fractal analysis of sixteen 3D images (eight for benign melanoma and eight for malignant) showed a capability of pathology of melanoma: melanin density and size become larger during the melanoma growth, and the melanin distribution also becomes more chaotic and unregulated. The results suggested new options for monitoring the melanoma growth and also for the melanoma diagnosis.

The use of reflectance confocal microscopy for examination of benign and malignant skin tumors

Reflectance confocal microscopy (RCM) is a modern, non-invasive diagnostic method that enables real-time imaging of epidermis and upper layers of the dermis with a nearly histological precision and high contrast. The application of this technology in skin imaging in the last few years has resulted in the progress of dermatological diagnosis, providing virtual access to the living skin erasing the need for conventional histopathology. The RCM has a potential of wide application in the dermatological diagnostic process with a particular reference to benign and malignant skin tumors. This article provides a summary of the latest reports and previous achievements in the field of RCM application in the diagnostic process of skin neoplasms. A range of dermatological indications and general characteristics of confocal images in various types of tumors are presented.

Actinic keratoses - a systemic review

Mainly elderly people with pale skin are affected by actinic keratoses (AK). Due to the demographic change, the prevalence of AK increased over the last years. An established risk factor is chronic UV-exposure (outdoor workers) inducing mutations of the tumor suppressor gene TP53 and the oncogene H-Ras. This leads to an intraepidermal proliferation of atypical keratinocytes. The term “field cancerization” characterises the presentation of multiple AK in UV-exposed areas. AK are also termed squamous cell carcinoma (SCC) in situ. The risk for AK turning into a SCC is 6-10%. In order to avoid invasive growth, an early treatment is recommended. During the last years multiple therapeutic options have been established. Depending on the clinical extent, lesion- or field-directed therapies with excellent clinical response and cosmetic results are available.

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.

Confocal laser scanning microscopy in vivo for diagnosing melanocytic skin neoplasms

The authors discuss the use of confocal laser scanning microscopy in vivo (CLSM) for diagnosing melanocytic skin neoplasms and its value for early diagnostics of melanoma. CLSM is an innovation noninvasive visual examination method for real-time multiple and painless examinations of the patient’s skin without injuring the skin integument. The method ensures early diagnostics of skin melanomas with high sensitivity and specificity, which makes it possible to use CLSM for screening melanocytic skin neoplasms for the sake of the early onset of treatment to save patient life and health.

Application of Confocal Laser Scanning Microscopy in Biology and Medicine

Fluorescence confocal laser scanning microscopy and reflectance confocal laser scanning microscopy are up-to-date highend study methods. Confocal microscopy is used in cell biology and medicine. By using confocal microscopy, it is possible to study bioplasts and localization of protein molecules and other compounds relative to cell or tissue structures, and to monitor dynamic cell processes. Confocal microscopes enable layer-by-layer scanning of test items to create demonstrable 3D models. As compared to usual fluorescent microscopes, confocal microscopes are characterized by a higher contrast ratio and image definition.

Detection of living Sarcoptes scabiei larvae by reflectance mode confocal microscopy in the skin of a patient with crusted scabies

Scabies is an intensely pruritic disorder induced by a delayed type hypersensitivity reaction to infestation of the skin by the mite Sarcoptes scabiei. The diagnosis of scabies is established clinically and confirmed by identifying mites or eggs by microscopic examination of scrapings from the skin or by surface microscopy using a dermatoscope. Reflectance-mode confocal microscopy is a novel technique used for noninvasive imaging of skin structures and lesions at a resolution compatible to that of conventional histology. Recently, the technique was employed for the confirmation of the clinical diagnosis of scabies.We demonstrate the first ever documentation of a larva moving freely inside the skin of a patient infected with scabies.

Reflectance confocal microscopy for quantification of Sarcoptes scabiei in Norwegian scabies

BACKGROUND AND OBJECTIVES

In vivo reflectance-mode confocal microscopy (RCM) can be used for the diagnosis of scabies. This study quantifies S. scabiei and its eggs and droppings in a patient affected by Norwegian Scabies (NS), and describes their distribution within the epidermis and in different body areas.

METHODS

Different skin sites were randomly chosen in four sections (head, upper limbs, trunk and inferior limbs) of the body surface area (BSA) to acquire a total of 60 RCM z-stacks. The number of mites and eggs, the presence of droppings, as well as the minimum epidermal depth at which mites, eggs and faeces were detectable, was established for each z-stack. The total number of mites and eggs on the entire BSA was calculated considering the weighted mean for the four sections of the BSA.

RESULTS

A total of 15.8 millions of S. scabiei and 7.2 millions of eggs were calculated. Mites, eggs and faeces were homogeneously distributed all over the body surface. Droppings, easily recognized by the RCM, were present in more than an half of the analyzed cutaneous sites and were associated with the presence of parasites (chi-squared test, P = 0.002).

CONCLUSIONS

Our study illustrates the ability of RCM to identify, locate, and quantify the various forms of S. scabiei in human skin. NS is an extremely contagious disease, considering that the number of mites can be around 15.8 millions. Moreover, all areas of the body are parasitized in NS, including the face.

Combining in vivo reflectance with fluorescence confocal microscopy provides additive information on skin morphology

BACKGROUND

Within the last decade, confocal microscopy has become a valuable non-invasive diagnostic tool in imaging human skin in vivo. Of the two different methods that exist, reflectance confocal microscopy (RCM) displays the backscattering signal of naturally occurring skin components, whereas fluorescence confocal microscopy (FCM) provides contrast by using an exogenously applied fluorescent dye.

METHODOLOGY

A newly developed multilaser device, in which both techniques are implemented, has been used to combine both methods and allows to highlight different information in one image. In our study, we applied the fluorophore sodium fluorescein (SFL) intradermally on forearm skin of 10 healthy volunteers followed by fluorescence and reflectance imaging.

RESULTS

In fluorescence mode the intercellular distribution of SFL clearly outlines every single cell in the epidermis, whereas in reflectance mode keratin and melanin-rich cells and structures provide additional information. The combination of both methods enables a clear delineation between the cell border, the cytoplasm and the nucleus. Imaging immediately, 20, 40 and 60 minutes after SFL injection, represents the dynamic distribution pattern of the dye.

CONCLUSION

The synergism of RCM and FCM in one device delivering accurate information on skin architecture and pigmentation will have a great impact on in vivo diagnosis of human skin in the future.

In vivo reflectance confocal microscopy: usefulness for diagnosing hair diseases

BACKGROUND

Reflectance confocal laser scanning microscopy (R-CSLM) is a new diagnostic technique which allows visualization of "optical intersections" within the epidermis and superficial layers of the dermis. Outlines of cells and their architecture are imaged and may be analyzed both horizontally and vertically to the skin surface. The method proved useful in early melanoma detection. We evaluated the potential usefulness of this method in a short series of patients with hair diseases.

MAIN OBSERVATIONS

Two healthy persons and 6 patients with hair diseases (1 with alopecia areata, 1 with androgenic alopecia and 4 with genetic hair shaft abnormalities) were examined with the use of Vivascope 1500. In all patients one scalp location and one location in the mid forearm were evaluated. R-CSLM examination gave in all cases high quality images of the hair shaft intersections, at 1µm intervals, which allowed detailed analysis of the hair structure. Hair follicles could be partly visualized at a depth of up to 200µm, which allowed analysis of only superficial parts of the hair follicles. An additional hurdle was bright reflection within the follicular ostia, which decreased the perception of details in these images. Hair could be best visualized, when analyzed on flat surfaces. Receiving good quality images from convex surfaces on the scalp required additional effort from the patient (to not move) and from the physician (to obtain best possible fit of the "optic window" to the scalp).

CONCLUSIONS

These preliminary data show that R-CSLM may develop into a valuable tool in evaluation of hair shaft diseases. Further development is needed to apply this technique in abnormalities of the hair follicle and the perifollicular area.

Stereological estimation of epidermal volumes and dermo-epidermal surface area in normal skin

Quantitative morphological studies of the healthy epidermis are essential in providing a range of parameter estimates that can be considered within the range of normality. Stereology is a set of statistical tools that provides potentially unbiased and precise estimates of 3-dimensional tissue characteristics from 2-dimensional sections. We set out to establish reference values for the volume of the viable epidermis contained within a four-millimetre punch biopsy (V(epi)), the volume of the stratum corneum (V(SC)) and the surface area of the dermo-epidermal junction(A(DEJ)) in 4 predetermined body regions by use of stereology. Four-millimetre punch biopsies were taken from 20 freshly diseased corpses, fixed in formalin and embedded in paraffin. V(epi), V(SC) and A(DEJ) were established stereologically for all 4 body locations followed by pairwise comparison of means after Bonferroni correction. V(epi) was significantly larger in the sole compared to all other body locations (p < 0.01). Furthermore, linear regression analysis showed a strong linear relationship between V(epi) and V(SC) in the sole (r = 0.70). Our results suggest that the viable layers of the epidermis might also serve a mechanical function, either directly or by providing the stratum corneum with keratinocytes to support the hyperkeratosis in the weight-bearing parts of the skin.

Intradermal indocyanine green for in vivo fluorescence laser scanning microscopy of human skin: a pilot study

Background

In clinical diagnostics, as well as in routine dermatology, the increased need for non-invasive diagnosis is currently satisfied by reflectance laser scanning microscopy. However, this technique has some limitations as it relies solely on differences in the reflection properties of epidermal and dermal structures. To date, the superior method of fluorescence laser scanning microscopy is not generally applied in dermatology and predominantly restricted to fluorescein as fluorescent tracer, which has a number of limitations. Therefore, we searched for an alternative fluorophore matching a novel skin imaging device to advance this promising diagnostic approach.

Methodology/Principal Findings

Using a Vivascope®-1500 Multilaser microscope, we found that the fluorophore Indocyanine-Green (ICG) is well suited as a fluorescent marker for skin imaging in vivo after intradermal injection. ICG is one of few fluorescent dyes approved for use in humans. Its fluorescence properties are compatible with the application of a near-infrared laser, which penetrates deeper into the tissue than the standard 488 nm laser for fluorescein. ICG-fluorescence turned out to be much more stable than fluorescein in vivo, persisting for more than 48 hours without significant photobleaching whereas fluorescein fades within 2 hours. The well-defined intercellular staining pattern of ICG allows automated cell-recognition algorithms, which we accomplished with the free software CellProfiler, providing the possibility of quantitative high-content imaging. Furthermore, we demonstrate the superiority of ICG-based fluorescence microscopy for selected skin pathologies, including dermal nevi, irritant contact dermatitis and necrotic skin.

Conclusions/Significance

Our results introduce a novel in vivo skin imaging technique using ICG, which delivers a stable intercellular fluorescence signal ideal for morphological assessment down to sub-cellular detail. The application of ICG in combination with the near infrared laser opens new ways for minimal-invasive diagnosis and monitoring of skin disorders.

In vivo monitoring of epidermal absorption of hazardous substances by confocal Raman micro-spectroscopy

BACKGROUND

Presently, percutaneous absorption of potentially hazardous chemicals in humans can only be assessed in animal experiments, in vitro, or predicted mathematically. Our aim was to demonstrate the proof-of-principle of a novel quantitative in vivo assay for percutaneous absorption: confocal Raman micro-spectroscopy (CRS). The advantages and limitations of CRS for health risk assessments are discussed.

PATIENTS AND METHODS

2-butoxyethanol, toluene, and pyrene were applied in pure form, diluted in water, or in ethanol on the skin of three healthy volunteers. CRS measurements were done following application for 15 min and 3 hours. The concentrations of the three substances as a function of distance to the skin surface were calculated and further analyzed with regard to mass transport into the stratum corneum (μg/cm(2)) and the flux through the stratum corneum (μg/cm(2)h). The results were compared with the available data from literature.

RESULTS

Considering the preliminary nature of these data, good accordance with data from the literature was observed. In addition, we observed that 2-butoxyethanol penetrates markedly faster when dissolved in water as compared to ethanol. This observation is also in agreement with previous results.

CONCLUSIONS

CRS has the potential to provide fast, accurate and reliable results for advanced studies of in vivo percutaneous absorption kinetics of hazardous substances in human skin. This will require further research with other substances and under differing conditions.

Advances in bio-optical imaging for the diagnosis of early oral cancer

Oral cancer is among the most common malignancies worldwide, therefore early detection and treatment is imperative. The 5-year survival rate has remained at a dismal 50% for the past several decades. The main reason for the poor survival rate is the fact that most of the oral cancers, despite the general accessibility of the oral cavity, are not diagnosed until the advanced stage. Early detection of the oral tumors and its precursor lesions may be the most effective means to improve clinical outcome and cure most patients. One of the emerging technologies is the use of non-invasive in vivo tissue imaging to capture the molecular changes at high-resolution to improve the detection capability of early stage disease. This review will discuss the use of optical probes and highlight the role of optical imaging such as autofluorescence, fluorescence diagnosis (FD), laser confocal endomicroscopy (LCE), surface enhanced Raman spectroscopy (SERS), optical coherence tomography (OCT) and confocal reflectance microscopy (CRM) in early oral cancer detection. FD is a promising method to differentiate cancerous lesions from benign, thus helping in the determination of adequate resolution of surgical resection margin. LCE offers in vivo cellular imaging of tissue structures from surface to subsurface layers and has demonstrated the potential to be used as a minimally invasive optical biopsy technique for early diagnosis of oral cancer lesions. SERS was able to differentiate between normal and oral cancer patients based on the spectra acquired from saliva of patients. OCT has been used to visualize the detailed histological features of the oral lesions with an imaging depth down to 2–3 mm. CRM is an optical tool to noninvasively image tissue with near histological resolution. These comprehensive diagnostic modalities can also be used to define surgical margin and to provide a direct assessment of the therapeutic effectiveness.

Rheological Innovations for Characterizing Food Material Properties

Rheological methods are continually evolving to encompass novel technologies and measurement methods. This review highlights novel techniques used to analyze the rheological properties of foods over the previous decade. Techniques reviewed include large amplitude oscillatory shear (LAOS) testing and rheological techniques coupled with other measurement methods, such as microscopy and nuclear magnetic resonance (NMR). Novel techniques are briefly overviewed and discussed in terms of advantages and disadvantages, previous use, and suggested future utilization.

Quantitative analysis on collagen morphology in aging skin based on multiphoton microscopy

Multiphoton microscopy was employed for monitoring the structure changes of mouse dermis collagen in the intrinsic- or the extrinsic-age-related processes in vivo. The characteristics of textures in different aging skins were uncovered by fast Fourier transform in which the orientation index and bundle packing of collagen were quantitatively analyzed. Some significant differences in collagen-related changes are found in different aging skins, which can be good indicators for the statuses of aging skins. The results are valuable to the study of aging skin and also of interest to biomedical photonics.

State of the art in non-invasive imaging of cutaneous melanoma

BACKGROUND

This review focuses on looking at recent developments in the non-invasive imaging of skin, in particular at how such imaging may be used at present or in the future to detect cutaneous melanoma.

METHODS

A MEDLINE search was performed for papers using imaging techniques to evaluate cutaneous melanoma, including melanoma metastasis.

RESULTS

Nine different techniques were found: dermoscopy, confocal laser scanning microscopy (including multiphoton microscopy), optical coherence tomography, high frequency ultrasound, positron emission tomography, magnetic resonance imaging, and Fourier, Raman, and photoacoustic spectroscopies. This review contrasts the effectiveness of these techniques when seeking to image melanomas in skin.

CONCLUSIONS

Despite the variety of techniques available for detecting melanoma, there remains a critical need for a high-resolution technique to answer the question of whether tumours have invaded through the basement membrane.

Light microscopy of the hair: a simple tool to "untangle" hair disorders

Light microscopy of the hair forms an important bedside clinical tool for the diagnosis of various disorders affecting the hair. Hair abnormalities can be seen in the primary diseases affecting the hair or as a secondary involvement of hair in diseases affecting the scalp. Hair abnormalities also form a part of various genodermatoses and syndromes. In this review, we have briefly highlighted the light microscopic appearance of various infectious and non-infectious conditions affecting the hair.

[Reflectance confocal microscopy in the diagnosis of cutaneous melanoma]

Skin melanoma is an international public health issue, with a considerable increase in frequency over the past few years. Early diagnosis and excision are essential for good patient prognosis. Over the past two decades dermoscopy has gained significance due to a major improvement in the accuracy of skin melanoma diagnosis in its early stage. However, there are some benign lesions of questionable dermoscopy, which may lead to the performance of unnecessary surgery. Recently, reflectance confocal microscopy has been introduced as a promising supplementary diagnostic method. It is a noninvasive, in vivo, simple, painless and quick exam. It is the only technique capable of identifying cellular structures and to examine the epidermis and papillary dermis with a resolution similar to that of histopathology, with a sensitivity of 97.3% and specificity of 72.3 % in the diagnosis of cutaneous melanoma. This is an important diagnostic tool, because it does not substitute post-surgical histopathological examination and allows for the rational assessment of lesions of questionable dermoscopy, thus avoiding unnecessary surgical procedures.

Infant skin microstructure assessed in vivo differs from adult skin in organization and at the cellular level

Functional differences between infant and adult skin may be attributed to putative differences in skin microstructure. The purpose of this study was to examine infant skin microstructure in vivo and to compare it with that of adult skin. The lower thigh area of 20 healthy mothers (ages 25-43) and their biological children (ages 3-24 months) was examined using in vivo noninvasive methods including fluorescence spectroscopy, video microscopy, and confocal laser scanning microscopy. Stratum corneum and supra-papillary epidermal thickness as well as cell size in the granular layer were assessed from the confocal images. Adhesive tapes were used to remove corneocytes from the outer-most layer of stratum corneum and their size was computed using image analysis. Surface features showed differences in glyph density and surface area. Infant stratum corneum was found to be 30% and infant epidermis 20% thinner than in adults. Infant corneocytes were found to be 20% and granular cells 10% smaller than adult corneocytes indicating a more rapid cell turnover in infants. This observation was confirmed by fluorescence spectroscopy. Dermal papillae density and size distribution also differed. Surprisingly, a distinct direct structural relationship between the stratum corneum morphology and the dermal papillae was observed exclusively in infant skin. A change in reflected signal intensity at approximately 100 mum indicating the transition between papillary and reticular dermis was evident only in adult skin. We demonstrate in vivo qualitative and quantitative differences in morphology between infant and adult skin. These differences in skin microstructure may help explain some of the reported functional differences.

Multiphoton laser scanning microscopy of localized scleroderma

BACKGROUND/PURPOSE

A real-time, non-invasive method will confer a benefit for the diagnosis and treatment of localized scleroderma (LS) in the clinic. The aim of this work was to demonstrate the potential of multiphoton laser scanning microscopy (MPLSM) for diagnosing LS and monitoring the treatment response in vivo.

METHODS

Three sclerodermatous skin specimens and two normal skin specimens were investigated using MPLSM based on two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG). MPLSM consists of a femtosecond Ti:sapphire laser and a scanning inverted microscope. Several parameters such as the epidermal thickness, the orientation ratio index of collagen bundles (ORICB), the spacing of collagen fibrin as well as the SHG to TPEF index of the dermis (STID) were developed to quantitatively discriminate the sclerodermatous skin from the normal skin.

RESULTS

The morphological differences were visualized obviously in the TPEF/SHG images of human skin (normal and sclerodermatous). The values of the developed parameters in normal skin were significantly different from that in sclerodermatous skin (P<0.05).

CONCLUSION

MPLSM could discriminate the sclerodermatous skin from the normal skin. With the advent of the clinical portability of typical MPLSM, this technique has great potential for application in the in vivo diagnosis of LS as well as for monitoring the treatment response.

Wavelength effects on contrast observed with reflectance in vivo confocal laser scanning microscopy

BACKGROUND/PURPOSE

The ability to optically section live biological tissue in vivo with laser light is made possible by confocal laser scanning microscopy (CLSM). In this work, the effects of changing the wavelength of incident light used for CLSM imaging of human skin are reported and analyzed.

METHODS

Optical phantoms and the skin of eight human volunteers were imaged using CLSM systems having three different incident light wavelengths (405, 785, and 830 nm).

RESULTS

Qualitative and quantitative differences were observed between images obtained at each wavelength, despite the proximity of the two near infrared 785 and 830 nm wavelengths. Furthermore, the penetration depth achieved with the 405 nm CLSM permitted imaging into the papillary dermis.

CONCLUSION

The laser wavelength used in CLSM reflectance imaging is important to properly understand and resolve different biological structures within human skin.

Full-field optical coherence tomography for the rapid estimation of epidermal thickness: study of patients with diabetes mellitus type 1

Changes in morphology of the skin are an important factor that can affect non-invasive measurements performed through this organ, in particular for glucose monitoring in e.g. patients with diabetes mellitus. A characterization technique for non-contact in vivo profiling of the superficial skin layers can be beneficial for evaluation of the performance of such measurement systems. We applied a full-field optical coherence tomography (OCT) system followed by the fully automatic processing for this task. With the developed procedure, non-invasive quantification of the skin morphology can be performed within a few minutes. The dorsal skin of the upper arm of 22 patients with Type 1 Diabetes Mellitus was investigated with an OCT system and with a commercially available dermatological laser scanning confocal microscope (CM) as a reference method. The estimates of epidermal thickness from OCT were compared with the results of expert-assisted analysis of confocal images. The highest correlation with the CM measurements has been obtained for the distance from the entrance peak to the first minimum of the OCT reflection profile (R2 = 0.657, p < 0.0001). In this specific patient group, we have observed a statistically significant correlation of the subjects' body mass index with the distance from the entrance peak to the dermal reflection peak in the OCT profile (p = 0.010). Furthermore, the same OCT parameter is negatively correlated with age with marginal statistical significance (p = 0.062). At the same time, no relation of diabetes-related parameters (duration of disease and concentration of glycated haemoglobin) to the skin morphology observed with the OCT and CM was found.

Optical coherence tomography imaging of psoriasis vulgaris: correlation with histology and disease severity

Epidermal thickness (ET) has been suggested as a surrogate measure of psoriasis severity. Optical coherence tomography (OCT) is a recent imaging technology that provides real-time skin images to a depth of 1.8 mm with a micrometre resolution. OCT may provide an accurate in vivo measure of ET. It is, therefore, speculated that OCT may be used in the assessment of psoriasis vulgaris. A total of 23 patients with psoriasis vulgaris were systematically evaluated by OCT imaging and skin biopsy during treatment. Biopsies were graded for disease severity, and additional evaluation was done by the physician via psoriasis area and severity index (PASI) score, and by the patient through measures such as self-administered PASI, psoriasis life stress inventory index and dermatology life quality index. ET was calculated from OCT images. In comparison to normal skin, psoriasis appeared with a more irregular surface with a stronger entrance signal, a serrated dermo-epidermal junction was found and a less signal intensity in the dermis as shown in OCT images. ET measured in untreated plaques was thicker reflecting epidermal hyperproliferation and inflammation. The changes were significantly correlated with the biopsy grading (r (2) = 0.41, p = 0.001) and ET significantly decreased with treatment (p = 0.0001). ET correlated significantly with self-reported measures of disease severity, but not with physician-assessed global PASI. The data suggest that OCT may be used to measure ET in psoriasis and the measurements correlate with several other parameters of disease severity. This implies that OCT assessment of psoriatic plaques may provide a useful method for non-invasive in vivo method to follow the evolution of psoriasis lesions.

Comparison of Cornea Module and DermaInspect for noninvasive imaging of ocular surface pathologies

Minimally invasive imaging of ocular surface pathologies aims at securing clinical diagnosis without actual tissue probing. For this matter, confocal microscopy (Cornea Module) is in daily use in ophthalmic practice. Multiphoton microscopy is a new optical technique that enables high-resolution imaging and functional analysis of living tissues based on tissue autofluorescence. This study was set up to compare the potential of a multiphoton microscope (DermaInspect) to the Cornea Module. Ocular surface pathologies such as pterygia, papillomae, and nevi were investigated in vivo using the Cornea Module and imaged immediately after excision by DermaInspect. Two excitation wavelengths, fluorescence lifetime imaging and second-harmonic generation (SHG), were used to discriminate different tissue structures. Images were compared with the histopathological assessment of the samples. At wavelengths of 730 nm, multiphoton microscopy exclusively revealed cellular structures. Collagen fibrils were specifically demonstrated by second-harmonic generation. Measurements of fluorescent lifetimes enabled the highly specific detection of goblet cells, erythrocytes, and nevus-cell clusters. At the settings used, DermaInspect reaches higher resolutions than the Cornea Module and obtains additional structural information. The parallel detection of multiphoton excited autofluorescence and confocal imaging could expand the possibilities of minimally invasive investigation of the ocular surface toward functional analysis at higher resolutions.

Reflectance confocal microscopy for in vivo skin imaging

Reflectance confocal microscopy (RCM) is a novel noninvasive technique for "in vivo" examination of the skin. In a confocal microscope, near- infrared light from a diode laser is focused on a microscopic skin target. As this light passes between cellular structures having different refraction indexes, it is naturally reflected, and this reflected light is then captured and recomposed into a two-dimensional gray scale image by computer software. Focusing the microscope (adjusting the focal point on the z-axis) allows images to be obtained of different levels within the skin. Commercially available microscope systems of this type can create images with enough detail for use in histological analysis. The first investigations using these microscopes served to identify the appearance of the various cell populations living in the different layers of normal skin. Today, the main interest has become focused on the use of these microscopes as a diagnostic tool: a means of investigating benign and malignant tumors of melanocytes and keratinocytes, and, more importantly, the findings of this field of study can be used to develop a diagnostic algorithm which would be not only highly sensitive but specific as well. The aim of the paper is to provide an updated literature review and an in-depth critique of the state-of-the-art of RCM for skin cancer imaging with a critical discussion of the possibilities and limitations for clinical use.