Skin dark spot mapping and evaluation of brightening product efficacy using Line-field Confocal Optical Coherence Tomography (LC-OCT)

BACKGROUND

Facial dark spots remain a significant challenge for the cosmetic industry, in terms of providing effective treatment. Using Line-field Confocal Optical Coherence Tomography (LC-OCT), we investigated the internal structural features of photo-aging spot areas and evaluated the efficacy of a skin-brightening cosmetic product.

MATERIALS AND METHODS

Twenty-six Asian female volunteers, aged between 29 and 65 years, applied a cosmetic product on their entire face twice a day for 2 months. LC-OCT was used to evaluate the dermal-epidermal junction (DEJ) undulation and the volume density of melanin in the epidermis at D0 and D56. Skin brightening and redness were also assessed by photography (SkinCam).

RESULTS

Using LC-OCT technology, various microscopic dark spot morphologies, spanning from minimally deformed DEJ to complex DEJ patterns, were identified. Dark spots characterized by slight deformities in the DEJ were predominantly observed in the youngest age group, while older volunteers displayed a wavier pattern. Furthermore, a total of 44 spots were monitored to evaluate the brightening product efficacy. A statistically significant reduction in melanin volumetric density of 7.3% in the spots and 12.3% in their surrounding area was observed after 56 days of product application. In line with these results, an analysis of color parameters using SkinCam reveals a significant increase in brightening and decrease in redness in both pigmented spots and the surrounding skin following application.

CONCLUSIONS

LC-OCT proves to be a valuable tool for in-depth dark spots characterization and assessment of skin brightening products, enabling various applications in the field of dermatological sciences.

Line-Field Confocal Optical Coherence Tomography (LC-OCT) for Skin Imaging in Dermatology

Line-field confocal optical coherence tomography (LC-OCT) is a non-invasive optical imaging technique based on a combination of the principles of optical coherence tomography and reflectance confocal microscopy with line-field illumination, which can generate cell-resolved images of the skin in vivo. This article reports on the LC-OCT technique and its application in dermatology. The principle of the technique is described, and the latest technological innovations are presented. The technology has been miniaturized to fit within an ergonomic handheld probe, allowing for the easy access of any skin area on the body. The performance of the LC-OCT device in terms of resolution, field of view, and acquisition speed is reported. The use of LC-OCT in dermatology for the non-invasive detection, characterization, and therapeutic follow-up of various skin pathologies is discussed. Benign and malignant melanocytic lesions, non-melanocytic skin tumors, such as basal cell carcinoma, squamous cell carcinoma and actinic keratosis, and inflammatory and infectious skin conditions are considered. Dedicated deep learning algorithms have been developed for assisting in the analysis of LC-OCT images of skin lesions.

Line-field confocal optical coherence tomography coupled with artificial intelligence algorithms to identify quantitative biomarkers of facial skin ageing

Quantitative biomarkers of facial skin ageing were studied from one hundred healthy Caucasian female volunteers, aged 20-70 years, using in vivo 3D Line-field Confocal Optical Coherence Tomography (LC-OCT) imaging coupled with Artificial Intelligence (AI)-based quantification algorithms. Layer metrics, i.e. stratum corneum thickness (SC), viable epidermal thickness and Dermal-Epidermal Junction (DEJ) undulation, as well as cellular metrics were measured for the temple, cheekbone and mandible. For all three investigated facial areas, minimal age-related variations were observed in the thickness of the SC and viable epidermis layers. A flatter and more homogeneous epidermis (decrease in the standard deviation of the number of layers means), a less dense cellular network with fewer cells per layer (decrease in cell surface density), and larger and more heterogeneous nuclei within each layer (increase in nuclei volume and their standard deviation) were found with significant variations with age. The higher atypia scores further reflected the heterogeneity of nuclei throughout the viable epidermis. The 3D visualisation of fine structures in the skin at the micrometric resolution and the 1200 µm × 500 µm field of view achieved with LC-OCT imaging enabled to compute relevant quantitative biomarkers for a better understanding of skin biology and the ageing process in vivo.

Line-field confocal optical coherence tomography (LC-OCT): principles and practical use

Line-field confocal optical coherence tomography (LC-OCT) is a non-invasive optical imaging technique based on a combination of the optical principles of optical coherence tomography and reflectance confocal microscopy with line-field illumination, which can generate cell-resolved images of the skin, in vivo, in vertical section, horizontal section and in three dimensions. This article reviews the optical principles of LC-OCT, including low coherence interferometry, confocal filtering and line-field arrangement. The optical setup allowing for the acquisition of color images of the skin surface in parallel with LC-OCT images, without compromising LC-OCT performance, is also presented. Practical use of LC-OCT is demonstrated through an overview of the workflow of examining a patient using a commercial handheld LC-OCT probe (deepLive™, DAMAE Medical), from creating the patient record in the software, acquiring the images, to reviewing and interpreting the images. LC-OCT can generate a significant amount of data, making automated deep learning algorithms particularly relevant for assisting in the analysis of LC-OCT images. A review of algorithms developed for skin layer segmentation, keratinocyte nuclei segmentation, and automatic detection of atypical keratinocyte nuclei is provided.

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.

Non-invasive scoring of cellular atypia in keratinocyte cancers in 3D LC-OCT images using Deep Learning

Diagnosis based on histopathology for skin cancer detection is today's gold standard and relies on the presence or absence of biomarkers and cellular atypia. However it suffers drawbacks: it requires a strong expertise and is time-consuming. Moreover the notion of atypia or dysplasia of the visible cells used for diagnosis is very subjective, with poor inter-rater agreement reported in the literature. Lastly, histology requires a biopsy which is an invasive procedure and only captures a small sample of the lesion, which is insufficient in the context of large fields of cancerization. Here we demonstrate that the notion of cellular atypia can be objectively defined and quantified with a non-invasive in-vivo approach in three dimensions (3D). A Deep Learning (DL) algorithm is trained to segment keratinocyte (KC) nuclei from Line-field Confocal Optical Coherence Tomography (LC-OCT) 3D images. Based on these segmentations, a series of quantitative, reproducible and biologically relevant metrics is derived to describe KC nuclei individually. We show that, using those metrics, simple and more complex definitions of atypia can be derived to discriminate between healthy and pathological skins, achieving Area Under the ROC Curve (AUC) scores superior than 0.965, largely outperforming medical experts on the same task with an AUC of 0.766. All together, our approach and findings open the door to a precise quantitative monitoring of skin lesions and treatments, offering a promising non-invasive tool for clinical studies to demonstrate the effects of a treatment and for clinicians to assess the severity of a lesion and follow the evolution of pre-cancerous lesions over time.

Effect of a baking soda-peroxide dentifrice on post-surgical wound healing

PURPOSE

To investigate the effect of a baking soda-hydrogen peroxide (0.75%) dentifrice on wound healing, plaque formation, gingival inflammation, patient comfort, probing depth, and clinical attachment level following gingival flap surgery.

MATERIALS AND METHODS

A randomized, double-blind crossover study involving 25 patients requiring bilateral maxillary gingival flap surgery was completed. The effects of twice daily brushing with a baking soda-hydrogen peroxide dentifrice (Mentadent) or a placebo dentifrice (Crest) were observed over a 28-day post-surgical period. Gingival Index (GI), plaque index (PI), probing depth (PD), clinical attachment level (CAL) and gingival bleeding index (BI) were recorded pre-surgically and at day 28 for each surgical sextant. At days 7 and 14, soft tissue appearance/wound healing (STA) was assessed based on color and edema, PIs were determined and patient comfort was ascertained by report.

RESULTS

Post-surgical wound healing was statistically significantly improved at day 7 with the trend continuing to day 14 when Mentadent dentifrice was used as compared to Crest dentifrice. However, there was no statistical difference in the PI values between the test and control dentifrice throughout the study. Use of Mentadent may be an effective aid in the early phase of healing following gingival flap surgery.

Self-care: practical periodontal care in today's practice

The contemporary patient has come to accept a personal responsibility for his own health. In terms of periodontal health and disease the dentist should enable the patient to achieve and maintain periodontal health by advising and, where appropriate, prescribing agents for home use. Agents to control plaque, whether in the form of rinses, pastes, gels or other formulations must demonstrate certain properties and characteristics. The testing, availability and properties of some of these agents are discussed.

Clinical evaluation of anticalculus dentifrices

One hundred and eighty-seven patients participated in a six-month study to evaluate the calculus-inhibiting effect of a zinc citrate dentifrice compared to Crest Tartar Control and a placebo, Crest Regular. The findings demonstrate a statistically significant calculus prevention benefit over Crest Regular for both Crest Tartar Control and a 2% zinc citrate/silica product. Compared to the control, the zinc citrate product reduced calculus formation by 32.3%, and Crest Tartar Control reduced it by 21.4%. These findings also demonstrate no statistically significant difference in stain or soft tissue status among the three dentifrices. All products were found to be safe to oral tissues and acceptable for taste.

A study of a sample of oral cancer in Israel

A review of data on oral cancer in Israel revealed a lower incidence and a later onset age than in other countries. These data are reviewed and consideration is given to the high prevalence of smoking and the low incidence of alcoholism in Israel.

Dentition, diet, tobacco, and alcohol in the epidemiology of oral cancer

Interview and dental examination data were gathered on 584 males with cancer of the oral cavity and on 1,222 control patients with nonneoplastic diseases at Roswell Park Memorial Institute, Buffalo, New York. No dietary characteristics distinguished cancer patients from controls. However, a higher risk of developing oral cancer was associated with heavy smoking, heavy drinking, and poor dentition. When controlled for the other factors, each factor carried a higher risk. Moreover, heavy smokers and heavy drinkers with poor dentition and males with all three traits had a substantially higher risk than would have been expected, if the traits were considered additively. The risk for males with all three traits was 7.7 times that of men with none of these traits.

Examiner standardization for caries studies

Examiners in clinical control programs customarily undergo an intensive period of training to standardize their interpretation of diagnostic criteria. Data are presented summarizing examiner error rates in calibration examinations and reversal rates in a field study.

Influence of a chlorhexidine and a zinc mouthrinse on gingivitis

The end point methodology did not indicate a difference between the agents. The prophylaxis effect was only demonstrable through 8 weeks, although the analysis of variance indicated a prophylaxis effect on gingival index throughout the study. An agent effect was not demonstrable in the study. The "positive control," chlorhexidine, did not give the same results in this brushing study as in previous no-brushing studies reported by Loe and by our group. One might conclude that the effectiveness of brushing in reducing gingivitis is greater than the effect of chlorhexidine. Decreasing plaque and gingivitis scores are seen with increasing time, probably reflecting increased subject interest and involvement in the study. Mere involvement in the study apparently produced a beneficial effect on gingival health. This "placebo effect" also has been noted in an earlier study. A similar decrease in plaque scores in a placebo group attributable to a general improvement of oral hygiene was reported by Gjermo and Rolla. The subjects who began the study with no calculus (prophylaxis group) had consistently lower calculus scores than those not given a prophylaxis. This difference became less distinct at later exams, as the treated group developed calculus. The agents, although ineffective under the test regimen produced no adverse effects.