Imaging of the skin with 20-MHz US

PURPOSE

The authors clinically evaluated a new high-frequency ultrasound (US) scanner to determine the value of US for dermatologic applications.

MATERIALS AND METHODS

A 20-MHz US scanner was used to visualize normal skin at eight sites in 10 healthy volunteers and to evaluate 200 skin lesions (45 malignant, 155 benign).

RESULTS

In normal skin, the dermis was markedly echogenic and sharply demarcated from hypoechoic subcutaneous fat. The epidermis was not resolved except on the palm and sole. Only three superficial lesions were not identified with US; evaluation of another three was limited by shadowing. Thickness of the lesions visualized was 0.2-26.0 mm (mean, 1.9 mm +/- 2.6). Most lesions (77%) were hypoechoic, 9% were anechoic, 12% had mixed echogenicity, and 2% were isoechoic or hyperechoic.

CONCLUSION

The diagnostic role of high-frequency US appears limited. It did not help differentiate benign from malignant lesions, but it did enable accurate delineation of deep margins of lesions and allowed noninvasive measurement of thickness. These features may help in the preoperative evaluation of skin tumors and in monitoring the response to therapy for certain inflammatory conditions.

Echographic evaluation with image analysis of normal skin: variations according to age and sex

In order to identify and characterize the sonographic variations between different age groups, 48 subjects, 24 aged 27-30, and 24 over 60, were studied with a 20-MHz B scanner on six skin sites. Images were evaluated by the instrument's standard programme and by a new image analysis software package enabling the characterization of steady structures or transitory functional aspects of skin reactions, by highlighting areas in which the echo amplitudes are included within selected values, and by calculating their extension. Three bands were selected as intervals of interest, respectively, highlighting hyporeflecting parts of the dermis, tissue reflecting with intermediate amplitude values and hyperreflecting epidermis and dermis. This method was employed to assess skin thickness, demonstrating its decrease in elderly skin, to characterize and quantify the hypoechogenic subepidermal band appearing in the elderly at volar and dorsal forearm skin, and to evaluate echogenicity of the upper and lower dermis. Our data show that there is a great regional variation in the behaviour of ultrasound reflection of elderly skin in respect to the skin of young subjects. However, a general trend can be identified, consisting in a shift from low-intensity ultrasound echoes, characteristic in the dermis of young subjects, to intermediate or high reflection amplitudes, which are more frequent in elderly skin. Thus, the echographic method provides two parameters for the evaluation of skin aging.(ABSTRACT TRUNCATED AT 250 WORDS)

Seventeen-point dermal ultrasound scoring system--a reliable measure of skin thickness in patients with systemic sclerosis

OBJECTIVE

Our objective was to develop a 17-site ultrasound method of measuring skin thickness in patients with systemic sclerosis (SSc) and to assess its inter- and intra-observer variability.

METHODS

Dermal thickness (using a 22 MHz ultrasound probe) was measured at 17 sites (corresponding to those assessed in the modified Rodnan skin score) in 39 patients with SSc (26 limited cutaneous, 13 diffuse) and 34 healthy controls. The sum of the thicknesses (at the 17 sites) and the maximal thickness were also documented. Because skin thickness varies between sites, each measurement was converted to a z-score. Inter- and intra-observer variability were assessed in 35 patients/33 controls, and 20 patients/15 controls respectively.

RESULTS

Measurement precision was good for the dermal measurements-intraclass correlation coefficients at the 17 sites ranged from 0.65 to 0.94 for the inter-observer variability (0.86 for maximum thickness) and from 0.55 to 0.96 for the intra-observer variability (0.92 for maximum thickness).

CONCLUSION

Our results suggest that the 17-point dermal ultrasound scoring system is extremely reliable and may therefore be a useful measure of outcome, including in clinical trials.

Ultrasonic propagation properties of excised human skin

Eight human skin samples were excised postmortem from the upper and lower back, chest and abdomen from two cadavers. The acoustical speed, attenuation and backscatter were measured as a function of frequency (20 to 30 MHz) at 100 positions on a uniform grid over a cross-sectional slice through each sample with the sound incident in a direction parallel to the skin surface. Measurements were made at 24 +/- 0.5 degrees C. Samples were then frozen, cut and stained for histological examination and quantification of fibrous proteins and fat content. The mean attenuation coefficients obtained for whole skin agreed well with previously published results. Employing the model alpha = alpha 1f" where alpha is the attenuation coefficient in decibels per centimeter, alpha 1 is the value of the attenuation coefficient at 1 MHz and f is frequency raised to the power n, mean values (+/- 1 standard deviation) for epidermis were alpha 1 = 0.44 +/- 0.26 and n = 1.55 +/- 0.12, and for dermis alpha 1 = 0.264 +/- 0.17 dB cm-1 and n = 1.69 +/- 0.084. Using a similar model the mean backscatter coefficient was defined by mu 1 = (5.01 +/- 25.76) x 10(-8) Sr-1 cm-1, n = 3.77 +/- 1.5 for the epidermis, and mu 1 = (1.79 +/- 19.5) x 10(-6) and n = 2.76 +/- 1.4 for the dermis. The speed of sound values fell within the range to be found in the literature with a mean value in the epidermis of 1645 m s-1 and in the dermis of 1595 m s-1. Significant, strong correlation existed between the spatially averaged fibrous protein content in the epidermis and dermis and the spatially averaged integrated attenuation measurements. Likewise, strong correlation existed between integrated backscatter and fibrous protein content in the epidermis but not in the dermis. Further research is required to confirm these preliminary findings and to evaluate the role of collagen fibre orientation as a source of variation in the backscattering coefficient of dermis.

Ultrasonographic subepidermal low-echogenic band, dependence of age and body site

BACKGROUND/PURPOSE

The presence of an age-dependent subepidermal low-echogenic band (SLEB) is well established at specific body sites. Several studies have also proposed it to be a marker of photoaging, but only few studies have included children in their material, and UVR exposure has predominantly been evaluated as differences between body sites with different UVR exposure. The aim of this study was to further investigate the existence of SLEB and exploring its relation to both age and body site/UVR exposure.

METHODS

In all 137 healthy volunteers from 4 to 68 years of age were included. In vivo high-frequency ultrasonography (B-mode, 20 MHz) was obtained from sun-exposed and sun-protected skin in a period with negligible environmental exposure to solar UVR. The SLEB was evaluated both visually and quantitatively.

RESULTS

We found a significant correlation between visual scoring of SLEB and dermal echogenicity, which supports the usefulness of SLEB scoring. We found that the grade (existence and development) of SLEB increased significantly with age at both the forehead and at the dorsal aspect of the forearm, where a well-defined SLEB was absent in children and present in over 50% of adults above the age of 40 years. No such age dependence was found either at the buttock or at the shoulder, and remarkably a well-defined SLEB was present in 37% of the adolescents at the buttock.

CONCLUSION

These results indicate that the age-related increase in SLEB grade at highly sun-exposed body sites might be attributed to UVR exposure. The presence of SLEB in both the young and at the sun-protected buttock points to a multifactorial etiology, where anatomical differences may play an important role as well as water content. SLEB might not be a very sensitive and specific marker of photoaging.

Phototherapy reduces the number of epidermal and CGRP-positive dermal nerve fibres

The purpose of this study was to gain an understanding of why phototherapy relieves itching. Skin samples (3 mm punch biopsies) from non-inflamed gluteal skin of 10 patients undergoing phototherapy were compared before and after 20 treatments. All the cutaneous nerve fibres here visualized by antibodies against PGP 9.5, sensory nerve fibres by antibodies against calcitonin gene-related peptide (CGRP) and capsaicin-sensitive primary nociceptive afferents by antibodies against VR1-receptor. Following treatment, the number of PGP 9.5-positive nerve fibres in the epidermis was reduced from 193 +/- 52 to 102 +/- 34 (p < 0.0001) and the number of CGRP-immunoreactive nerve fibres, which occurred only in dermis, was reduced from 28 +/- 15 to 22 +/- 7 (p = 0.04). The VR1-immunoreactive nerve fibres, some of them containing immunoreactivity to CGRP, were not affected. The success of phototherapy in combating itch may at least partly be linked with the reduction in the number of epidermal nerve fibres. The reduction in the number of CGRP-immunoreactive nerve fibres in the dermis may contribute to the beneficial effects of UV irradiation on the inflammatory process.

Epidermal and dermal effects of topical lactic acid

BACKGROUND

Many alpha-hydroxy acid products, containing low- or high-acid concentrations, are being used. It is not known whether different products perform differently or whether they modulate changes in both the epidermis and dermis.

OBJECTIVE

The purpose was to examine whether treatment with 5% and 12% lactic acid produces different cosmetic results and produces changes in the epidermis and dermis.

METHODS

Test participants applied either 5% or 12% lactic acid twice a day for 3 months. Changes in skin smoothness and texture, the depth and number of lines and wrinkles, and epidermal and dermal firmness and thickness were determined.

RESULTS

Treatment with 12% lactic acid resulted in increased epidermal and dermal firmness and thickness and clinical improvement in skin smoothness and in the appearance of lines and wrinkles. No dermal changes were observed after treatment with 5% lactic acid; however, similar clinical and epidermal changes were noted.

CONCLUSION

The results demonstrate that cosmetic benefits from the use of alpha-hydroxy acids are caused by modification of the skin surface, the epidermis and the dermis. Although 5% lactic acid modulates surface and epidermal changes, 12% lactic acid influences both the epidermis and the dermis.

Evidence for small fiber neuropathy in early Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is neurodegenerative movement disorder affecting primarily the central nervous system with several recognized non-motor symptoms that can occur at various stages of the disease. Recently it has been shown that patients with PD may be prone to peripheral nervous system pathology in the form of a peripheral neuropathy (PN). It is unclear if PN is an inherent feature of PD or if it is an iatrogenic effect of the mainstay PD treatment Levodopa.

METHODS

To determine if peripheral neuropathy occurs in early untreated PD we employed a case-control study design using gold standard tests for PN, including neurological examination according to the Utah Early Neuropathy Scale (UENS) and nerve conduction studies, as well as new, more sensitive and informative tests for PN including the skin biopsy and corneal confocal microscopy (CCM).

RESULTS

We studied 26 patients with PD and 22 controls using the neurological examination and nerve conduction studies (NCS) and found no significant difference between groups except for some reduced vibration sense in the PD group. Epidermal nerve densities in the skin biopsies were similar between our cohorts. However, using CCM - a more sensitive test and a surrogate marker of small fiber damage in PN, we found that patients with PD had significantly reduced corneal nerve fiber densities and lengths as compared to controls.

CONCLUSIONS

We conclude that our positive CCM results provide evidence of preclinical PN in newly diagnosed PD patients.

In vivo epidermal thickness measurement: ultrasound vs. confocal imaging

BACKGROUND/PURPOSE

In this study, in vivo skin imaging methods, ultrasound (US) and confocal microscopy (CM) were compared with regards to their accuracy in measuring the epidermal thickness. In addition an attempt was made to clarify the biological significance of the second echo-rich line observed on US skin images, i.e. whether it represents the dermal-epidermal junction or the papillar-reticular dermis limit.

METHODS

US images were obtained with an in-house device (22 MHz probe) and the CM images with the VivaScope 1000 (Lucid Inc., Rochester, NY, USA). Skin from the dorsal forearm, the back of hand and the palm skin of 11 subjects (25-40 years) were examined. Repeatability of the procedure and reproducibility of the results were evaluated on repeated measurements taken at 1-month interval.

RESULTS

Both techniques are correlated. When a CM measurement is performed from the stratum corneum (SC) surface to the bottom of the papillae, results obtained with US and CM are very similar. Thus, the second echo-rich line on US skin imaging is likely to reflect a virtual line joining the bottom of the papillae. CM is limited to the measurement of a relative thin epidermis, due to the signal-to-noise ratio, which decreases with depth. US technique offers a better repeatability and reproducibility, particularly for SC measurement. This is mainly due to the small size of the investigated field of view in CM.

CONCLUSIONS

This study confirms the accuracy of US and the feasibility of CM imaging techniques for in vivo epidermal thickness measurement. Echography probably measures a maximal epidermal thickness since it encompasses the bottom of the papillae.

Ultrasound-induced intercellular space widening in fish epidermis

Transmission electron microscopy was employed to determine the effects of therapeutic ultrasound (US) (I(sata) < or =2.2 W cm(-2), 3 MHz), sonicated at different angles and durations, on the external epithelia of fish skin. Sonication at 1.7 W cm(-2) (90 s), where the ultrasonic beam was perpendicular to the skin surface, produced minor intercellular space widening (ICSW), as well as the disruption of desmosomes connecting between the cells. Increasing the intensity to 2.2 W cm(-2) increased ICSW, the extent of which was positively correlated to the duration of exposure (30 to 90 s). Perpendicular sonication produced ICSW, almost exclusively between cells of the two outermost cell layers, parallel to the skin surface. Sonicating at 45 degrees (2.2 W cm(-2), 90 s) produced ICSW in deeper cell layers in the tissues, in which the spaces were at seemingly random orientations. Mucous cells and macrophages were also found to be damaged, as were apoptotic epidermal cells. The suggested mechanism for ICSW is the formation of transverse (shear) waves at the interface between the aquatic medium and the skin surface. The waves, which are damped out within a few cell layers, give rise to shear stresses that, in turn, cause strains that act to separate between cells and damage some of the relatively weaker cells.

Ultrasound-induced cavitation damage to external epithelia of fish skin

Transmission electron microscopy was used to show the effects of therapeutic ultrasound (< or = 1.0 W/cm2, 1 MHz) on the external epithelia of fish skin. Exposures of up to 90 s produced damage to 5 to 6 of the outermost layers. Negligible temperature elevations and lack of damage observed when using degassed water indicated that the effects were due to cavitation. The minimal intensity was determined for inducing cellular damage, where the extent and depth of damage to the tissues was correlated to the exposure duration. The results may be interpreted as a damage front, advancing slowly from the outer cells inward, presumably in association with the slow replacement of the perforated cell contents with the surrounding water. This study illustrates that a controlled level of microdamage may be induced to the outer layers of the tissues.

Ultrasound imaging of psoriatic skin: a noninvasive technique to evaluate treatment of psoriasis

BACKGROUND

The aim of our study was to image psoriasis plaques by ultrasound to assess the changes in psoriasis and to measure and quantify them objectively.

MATERIALS AND METHODS

Thirty-one psoriasis plaques were studied in 19 patients. Measurements of skin thickness were obtained with a high resolution B-mode echographic system.

RESULTS

Some changes were seen in psoriatic skin. A new structural element was observed: a wide subepidermal nonechogenic band. The other changes were a decrease in dermal echoes that were less intense and less dense, and an increase in the epidermal and dermal skin thicknesses. The skin thickness was increased in all psoriasis plaques as compared to apparently normal skin (P < 0.001). The average increase was 67% for whole skin and 200% for epidermis.

CONCLUSIONS

Ultrasound imaging of psoriatic skin allowed the identification of different skin changes induced by psoriasis, and particularly, the differentiation between epidermal and dermal alterations. We presume that epidermal thickness reflects epidermal proliferation and desquamation, and the increase in the dermal and whole skin thickness reflects infiltration. We feel that ultrasound imaging of psoriatic skin is a quantitative method that is as easy and noninvasive as the psoriasis area and severity index (PASI). It could be used for following up patients with psoriasis and could achieve widespread use, especially in research protocols.

In vivo stiffness measurement of epidermis, dermis, and hypodermis using broadband Rayleigh-wave optical coherence elastography

Traveling-wave optical coherence elastography (OCE) is a promising technique to measure the stiffness of biological tissues. While OCE has been applied to relatively homogeneous samples, tissues with significantly varying elasticity through depth pose a challenge, requiring depth-resolved measurement with sufficient resolution and accuracy. Here, we develop a broadband Rayleigh-wave OCE technique capable of measuring the elastic moduli of the 3 major skin layers (epidermis, dermis, and hypodermis) reliably by analyzing the dispersion of leaky Rayleigh surface waves over a wide frequency range of 0.1-10 kHz. We show that a previously unexplored, high frequency range of 4-10 kHz is critical to resolve the thin epidermis, while a low frequency range of 0.2-1 kHz is adequate to probe the dermis and deeper hypodermis. We develop a dual bilayer-based inverse model to determine the elastic moduli in all 3 layers and verify its high accuracy with finite element analysis and skin-mimicking phantoms. Finally, the technique is applied to measure the forearm skin of healthy volunteers. The Young's modulus of the epidermis (including the stratum corneum) is measured to be ∼ 4 MPa at 4-10 kHz, whereas Young's moduli of the dermis and hypodermis are about 40 and 15 kPa, respectively, at 0.2-1 kHz. Besides dermatologic applications, this method may be useful for the mechanical analysis of various other layered tissues with sub-mm depth resolution. STATEMENT OF SIGNIFICANCE: To our knowledge, this is the first study that resolves the stiffness of the thin epidermis from the dermis and hypodermis, made possible by using high-frequency (4 - 10 kHz) elastic waves and optical coherence elastography. Beyond the skin, this technique may be useful for mechanical characterizations of various layered biomaterials and tissues.

Evaluation of the atrophogenic potential of different glucocorticoids using optical coherence tomography, 20-MHz ultrasound and profilometry; a double-blind, placebo-controlled trial

BACKGROUND

Skin atrophy is one of the main side-effects of topical corticosteroid therapy. Although the use of high-frequency ultrasound is an established method that has been studied previously, it allows measurements of the slow-reacting dermal thickness only.

OBJECTIVES

To investigate the decreasing epidermal thickness, which occurs earlier, we used optical coherence tomography (OCT), a high-resolution noninvasive imaging technique, and compared it with 20-MHz ultrasound and profilometry.

PATIENTS/METHODS

In this double-blind placebo-controlled trial 20 healthy volunteers applied four different corticosteroids and the cream base formulation as placebo to the volar part of both arms once a day over a 4-week period. The epidermal thickness, the dermal thickness and the skin surface roughness were assessed using OCT, high-frequency ultrasound and profilometry.

RESULTS

Each of the three methods allowed the detection and monitoring of significant corticosteroid-induced skin atrophy and its reversibility. The changes correlated with the potency of the steroids. The epidermal thickness decreased significantly in all test areas, even in the placebo and the untreated fields. As expected, the reduction in epidermal thickness was more pronounced and could be detected earlier by OCT than the reduction of dermal thickness using ultrasound. The epidermal surface roughness investigated using profilometry showed a slight smoothing.

CONCLUSIONS

OCT allows a simple, fast and noninvasive in vivo measurement of the epidermal thickness. To evaluate the atrophogenic potential of corticosteroids it is more suitable than high-frequency ultrasound as epidermal thickness decreases earlier. In addition, epidermal thickness is a more sensitive indicator of steroid atrophy as the degree of thinning is much higher compared with the dermal atrophy. Profilometry might give further information; however, it would not be suitable for clinical use as the results were generally less pronounced. In the future, OCT might be useful to detect corticosteroid-induced side-effects at the beginning for monitoring the therapy.

On the equivalence and differences between laser Doppler flowmetry and laser speckle contrast analysis

Laser Doppler flowmetry (LDF) and laser speckle contrast analysis (LASCA) both utilize the spatiotemporal properties of laser speckle patterns to assess microcirculatory blood flow in tissue. Although the techniques analyze the speckle pattern differently, there is a close relationship between them. We present a theoretical overview describing how the LDF power spectrum and the LASCA contrast can be calculated from each other, and how both these can be calculated from an optical Doppler spectrum containing various degrees of Doppler shifted light. The theoretical relationships are further demonstrated using time-resolved speckle simulations. A wide range of Monte Carlo simulated tissue models is then used to show how perfusion estimates for LDF and LASCA are affected by changes in blood concentration and speed distribution, as well as by geometrical and optical properties. We conclude that perfusion estimates from conventional single exposure time LASCA are in general more sensitive to changes in optical and geometrical properties and are less accurate in the prediction of real perfusion changes, especially speed changes. Since there is a theoretical one-to-one relationship between Doppler power spectrum and contrast, one can conclude that those drawbacks with the LASCA technique can be overcome using a multiple exposure time setup.

Microdialysis technique as a method to study the percutaneous penetration of methyl nicotinate through excised human skin, reconstructed epidermis, and human skin in vivo

PURPOSE

The aim was to assess the feasibility of cutaneous microdialysis as a method to study percutaneous penetration of methyl nicotinate through human skin in vitro and in vivo.

METHODS

Microdialysis was applied in vitro in excised human skin, in isolated dermis, in reconstructed human epidermis and in vivo in the volar forearm skin of volunteers using methyl nicotinate (MN) as a model compound. After topical application of MN, aliquots of the perfusate were collected and analyzed for the presence of MN spectrophotometrically and by HPLC. In vivo, visual scoring and laser Doppler perfusion imaging (LDPI) were used to monitor the effects on skin blood flow.

RESULTS

In vitro, MN was detected in the dialysate after a 1 min exposure of excised skin to concentrations as low as 25 mM. Higher concentrations up to 500 mM showed increased levels. Prolongation of the application time to 60 min resulted in increased levels of MN in the perfusate as the duration of application increased. Reconstructed epidermis and isolated dermis showed an almost 2- and 20-fold higher penetration compared to excised skin, respectively. In vivo, LDPI measurements showed a rapid increase in skin blood flow after application of 25 to 100 mM MN for 1 min. MN was only detectable in the microdialysate after application of 100 mM for 10 min (two of three subjects).

CONCLUSIONS

Cutaneous microdialysis may be a tool for comparative studies linking responses in human skin in vivo to in vitro data using the same technique and endpoint.

Psoriasis skin biopsy image segmentation using Deep Convolutional Neural Network

BACKGROUND AND OBJECTIVE

Development of machine assisted tools for automatic analysis of psoriasis skin biopsy image plays an important role in clinical assistance. Development of automatic approach for accurate segmentation of psoriasis skin biopsy image is the initial prerequisite for developing such system. However, the complex cellular structure, presence of imaging artifacts, uneven staining variation make the task challenging. This paper presents a pioneering attempt for automatic segmentation of psoriasis skin biopsy images.

METHODS

Several deep neural architectures are tried for segmenting psoriasis skin biopsy images. Deep models are used for classifying the super-pixels generated by Simple Linear Iterative Clustering (SLIC) and the segmentation performance of these architectures is compared with the traditional hand-crafted feature based classifiers built on popularly used classifiers like K-Nearest Neighbor (KNN), Support Vector Machine (SVM) and Random Forest (RF). A U-shaped Fully Convolutional Neural Network (FCN) is also used in an end to end learning fashion where input is the original color image and the output is the segmentation class map for the skin layers.

RESULTS

An annotated real psoriasis skin biopsy image data set of ninety (90) images is developed and used for this research. The segmentation performance is evaluated with two metrics namely, Jaccard's Coefficient (JC) and the Ratio of Correct Pixel Classification (RCPC) accuracy. The experimental results show that the CNN based approaches outperform the traditional hand-crafted feature based classification approaches.

CONCLUSIONS

The present research shows that practical system can be developed for machine assisted analysis of psoriasis disease.

Line-field confocal optical coherence tomography as a tool for three-dimensional in vivo quantification of healthy epidermis: A pilot study

Epidermal three-dimensional (3D) topography/quantification has not been completely characterized yet. The recently developed line-field confocal optical coherence tomography (LC-OCT) provides real-time, high-resolution, in-vivo 3D imaging of the skin. This pilot study aimed at quantifying epidermal metrics (epidermal thicknesses, dermal-epidermal junction [DEJ] undulation and keratinocyte number/shape/size) using 3D LC-OCT. For each study participant (8 female, skin-type-II, younger/older volunteers), seven body sites were imaged with LC-OCT. Epidermal metrics were calculated by segmentations and measurements assisted by artificial intelligence (AI) when appropriate. Thicknesses of epidermis/SC, DEJ undulation and keratinocyte nuclei volume varied across body sites. Evidence of keratinocyte maturation was observed in vivo: keratinocyte nuclei being small/spherical near the DEJ and flatter/elliptical near the skin surface. Skin microanatomy can be quantified by combining LC-OCT and AI. This technology could be highly relevant to understand aging processes and conditions linked to epidermal disorders. Future clinical/research applications are to be expected in this scenario.

Transdermal delivery of poly-l-lysine by sonomacroporation

A feasibility study of using high-amplitude ultrasound (US) to deliver large molecules transdermally was undertaken. US (20 kHz) of intensity in the range between 2 to 50 W/cm(2) was used to increase the permeability of skin in vitro to large size molecules. For example, when 20-kHz, 5% duty cycle US at the spatial average and pulse-average intensity I(SAPA) = 19 W/cm(2) was applied for 10 min and the distance between the US source and the surface of a skin specimen was 2 mm, the skin permeability was calculated to be 0.5 +/- 0.2 cm/h and 8.5 +/- 4.2 cm/h, respectively, for poly l-lysine-fluorescein isothiocyanate (FITC) (51 kDa) and octa-1-lysine-FITC (2.5 kDa). Without application of US, the skin permeability of the above-mentioned molecules would be essentially zero. A transdermal flux enhancement occurring during the process reported here was much higher than that due to sonophoresis (I(SAPA) < 2 W/cm(2)) as reported in the literature. For comparison, for example, the skin permeability for delivering erythropoeitin (48 kDa) and insulin (6 kDa) reached 9.8 x 10(-6) and 3.3 x10(-3) cm/h, respectively, by using sonophoresis for 1 h US exposure. Experimental results from transdermal flux kinetics, and confocal microscopic cross-sectional and optical images, suggested that the formation of pores in the stratum corneum, whose size varies with skin samples, may be in the range of 1 to 100 microm. The confocal images also suggest the formation of microm-size pathways in epidermis during US exposure.

Confocal Raman spectroscopic imaging for in vitro monitoring of active ingredient penetration and distribution in reconstructed human epidermis model

Topically applied active cosmetic ingredients (ACI) or active pharmaceutical ingredients (API) efficacy is directly related to their efficiency of penetration in the skin. In vitro reconstructed human epidermis surrogate models offer in vivo like skin samples for transdermal studies. Using Delipidol®, an ACI currently used in the cosmetics industry, the capabilities to deliver accurate distribution maps and penetration profiles of this molecule by means of confocal Raman spectroscopic imaging have been demonstrated. Using a non-negative constrained least squares (NCLS) approach, contribution of specific molecules can be estimated at each point of spectral maps in order to deliver semi-quantitative heat maps representing the ACI levels in the different skin layers. The concentration profiles obtained are approximately single exponential for all 3 time points evaluated, with a consistent decay constant, which is independent of the sublayer structure. Notably, however, there is no significant penetration into the lower basal layers until a critical concentration is built up, after 3 hours. Combination of Raman confocal imaging with spectral unmixing methods such as NCLS is demonstrated to be a relevant approach for in vitro biological evaluation of cosmetic and pharmaceutical active ingredients and could easily be implemented as a screening tool for industrial use.

Deep-learning approach for automated thickness measurement of epithelial tissue and scab using optical coherence tomography

SIGNIFICANCE

In order to elucidate therapeutic treatment to accelerate wound healing, it is crucial to understand the process underlying skin wound healing, especially re-epithelialization. Epidermis and scab detection is of importance in the wound healing process as their thickness is a vital indicator to judge whether the re-epithelialization process is normal or not. Since optical coherence tomography (OCT) is a real-time and non-invasive imaging technique that can perform a cross-sectional evaluation of tissue microstructure, it is an ideal imaging modality to monitor the thickness change of epidermal and scab tissues during wound healing processes in micron-level resolution. Traditional segmentation on epidermal and scab regions was performed manually, which is time-consuming and impractical in real time.

AIM

We aim to develop a deep-learning-based skin layer segmentation method for automated quantitative assessment of the thickness of in vivo epidermis and scab tissues during a time course of healing within a rodent model.

APPROACH

Five convolution neural networks were trained using manually labeled epidermis and scab regions segmentation from 1000 OCT B-scan images (assisted by its corresponding angiographic information). The segmentation performance of five segmentation architectures was compared qualitatively and quantitatively for validation set.

RESULTS

Our results show higher accuracy and higher speed of the calculated thickness compared with human experts. The U-Net architecture represents a better performance than other deep neural network architectures with 0.894 at F1-score, 0.875 at mean intersection over union, 0.933 at Dice similarity coefficient, and 18.28  μm at an average symmetric surface distance. Furthermore, our algorithm is able to provide abundant quantitative parameters of the wound based on its corresponding thickness maps in different healing phases. Among them, normalized epidermal thickness is recommended as an essential hallmark to describe the re-epithelialization process of the rodent model.

CONCLUSIONS

The automatic segmentation and thickness measurements within different phases of wound healing data demonstrates that our pipeline provides a robust, quantitative, and accurate method for serving as a standard model for further research into effect of external pharmacological and physical factors.

Marked Changes in Lamellar Granule and Trans-Golgi Network Structure Occur during Epidermal Keratinocyte Differentiation

Epidermal lamellar granules transport various lipids, proteins, and protein inhibitors from the trans-Golgi network to the extracellular space, and play an important role in skin barrier formation. We elucidated the 3-dimensional structure of lamellar granules and the trans-Golgi network in normal human skin by focused ion beam scanning electron microscopy. Reconstructed focused ion beam scanning electron microscopy 3-dimensional images revealed that the overall lamellar granule structure changed from vesicular to reticular within the second layer of the stratum granulosum. Furthermore, the trans-Golgi network was well developed within this layer and spread through the cytoplasm with branched, tubular structures that connected to lamellar granules. Our study reveals the unique overall 3-dimensional structure of lamellar granules and the trans-Golgi network within the cells of the epidermis, and provides the basis for an understanding of the skin barrier formation.

Early detection of diabetic neuropathy by investigating CNFL and IENFD in thy1-YFP mice

Small fiber neuropathy is one of the most common and painful long-term complications of diabetes mellitus. Examination of the sub-basal corneal nerve plexus is a promising surrogate marker of diabetic neuropathy. To investigate the efficacy, reliability and reproducibility of in vivo corneal confocal microscopy (IVCCM), we used thy1-YFP mice, which express yellow fluorescence protein (YFP) in nerve fibers. 4 weeks after multiple low-dose injections of streptozotocin, thy1-YFP mice showed manifest diabetes. Subsequent application of insulin-releasing pellets for 8 weeks resulted in a significant reduction of blood glucose concentration and HbA_1c, a significant increase in body weight and no further increase in advanced glycation end products (AGEs). IVCCM, carried out regularly over 12 weeks and analyzed both manually and automatically, revealed a significant loss of corneal nerve fiber length (CNFL) during diabetes manifestation and significant recovery after insulin therapy. Ex vivo analyses of CNFL by YFP-based microscopy confirmed the IVCCM results (with high sensitivity between manual and automated approaches) but demonstrated that the changes were restricted to the central cornea. Peripheral areas, not accessible by IVCCM in mice, remained virtually unaffected. Because parallel assessment of intraepidermal nerve fiber density revealed no changes, we conclude that IVCCM robustly captures early signs of diabetic neuropathy.

Skin strata delineation in reflectance confocal microscopy images using recurrent convolutional networks with attention

Reflectance confocal microscopy (RCM) is an effective non-invasive tool for cancer diagnosis. However, acquiring and reading RCM images requires extensive training and experience, and novice clinicians exhibit high discordance in diagnostic accuracy. Quantitative tools to standardize image acquisition could reduce both required training and diagnostic variability. To perform diagnostic analysis, clinicians collect a set of RCM mosaics (RCM images concatenated in a raster fashion to extend the field view) at 4-5 specific layers in skin, all localized in the junction between the epidermal and dermal layers (dermal-epidermal junction, DEJ), necessitating locating that junction before mosaic acquisition. In this study, we automate DEJ localization using deep recurrent convolutional neural networks to delineate skin strata in stacks of RCM images collected at consecutive depths. Success will guide to automated and quantitative mosaic acquisition thus reducing inter operator variability and bring standardization in imaging. Testing our model against an expert labeled dataset of 504 RCM stacks, we achieved [Formula: see text] classification accuracy and nine-fold reduction in the number of anatomically impossible errors compared to the previous state-of-the-art.