Analysis of images supplied by Skincam® can record the changes of some scar features that occur over time. Comparisons with the assessments of dermatologist and patients' perception

The objective of the study was to assess in vivo the validity of a new imaging device in quantifying the scarring process over time and to compare its data with the expertise of dermatologist and patients' self‐appraisals.


| INTRODUC TI ON
Skin wound healing is an immune response to tissue injury that ends with wound closure and restores the skin barrier function to prevent infection. It is a complex process in three crucial steps to create a neat scar: inflammation, proliferation, and remodeling. Wound healing initially proceeds rapidly with re-epithelialization, whereas tissue remodeling occurs over a period of weeks to months to create a more attractive scar. 1,2 Burn wounds differ from post-surgical wounds. 3 Indeed, heat not only damages skin locally but has many generalized effects on the body, such as a septic shock, more specifically linked to heat-damaged tissues than other injuries (cuts, blowinduced wounds).
In term of treatment, massage during two to four weeks allow the improvement of post-surgical outcomes 4,5 such as thickness of scars, keloid formation, and over-corrected ptosis. Additionally, massage allows to reduce scar-related pain and itching, to alleviate patients' anxiety and to improve mood and mental status. 5,6 As companion of the massaging process, a basic skin care may provide a barrier in maintaining a moist micro-environment required for optimal healing, an important role during the remodeling phase of wound repair and throughout maturation. Although silicone sheets and gels are considered the gold standards for preventing excessive scarring, hydrating cream is considered as an equivalent occluding and hydrating properties to silicone products. This suggests that hydrating creams could be an alternative to silicones in scar prevention in addition to a soothing effect that enhances wound healing. 1 A skin injury can trigger an imperfect tissue repair, leading to scar formation. Scars developed from burn injuries, surgeries and traumatic events are known to have wide ranging effects on individuals. 7 As all forms of surgery result in scarring, which can have a strong impact on quality of life (QoL). Scars, in general, may profoundly impact physical, social, and cognitive functioning, affecting emotional well-being of patients. [8][9][10] Scar assessment is part of the ordinary evaluation of patients requiring rehabilitation after surgery. Basically, three criteria for evaluating scars include: (i) physical anatomical criteria of the scar (texture, pigmentation, thickness…), (ii) scar physiology (contraction, skin barrier…), and (iii) symptomatic or psychological criteria (itch, pain…). These different categories can be analyzed with both objective (devices, instruments) and subjective (scar scale) methods.
Usually, various physical anatomical features of scars are evaluated with the main ones being pigmentation, color/light reflection, vascularity, texture, pliability or elasticity, height or thickness and surface area. Instrumental methods such as spectrophotometry for scar color and light reflection, planimetry for scar surface area, ultrasonography for scar thickness is usually used for research purposes but more rarely in clinical practice. Subjective tools such as scar assessment scales are useful and very applicable in everyday clinical practice. 11,12 The VSS scale (Vancouver Scar Scale), based on the scoring of various elements such as (Vascularity, Pigmentation, and Pliability) remains the most used method in clinical practice for burn scars with a high reliability but is not often used for large or irregular scars. The POSAS (Patient and Observer Scar Assessment Scale) approach is also often used for surgical scars as the method is quite complete with both observer and patient scales-assessing for scars pain, itchiness, color, stiffness, roughness, irregularities, etc. 5,6,10,13,14 The aim of this paper is to present the possibilities of analyses offered by the SkinCam® device beyond microrelief, 15 to record the changes in some parameters of the scars over time and to complete the dermatologists' expertise. Here, images of the skin were acquired during a clinical study performed in the consumer agency facilities (Seoul, Korea). The major goal of this study was to record the changes in detected scars after regular applications of a hydrating cream, in two main dimensions: color and morphology (skin color, skin texture, skin roughness, on depth, size, and volume) present on the body in a panel of 37 subjects after 56 days. To achieve this investigation, images were acquired on D 0 (Baseline), D 28 (4 weeks), and D 56 (8 weeks), and their analysis was performed by Newtone Technologies.

| Subjects
The study took place in our research facilities in Seoul, Korea, between November 2021 and January 2022. 37 Korean women subjects aged 20-50y were recruited. All were not using (or no longer using since at least four months) a specific treatment of their scar.
All subjects received detailed information in Korean language of the goal and protocol of this non-invasive in vivo study. All gave their written informed consent before enrolment. The subjects presented closed scars of different characteristics, (i) developed within the last 5 months on average, (ii) due to post cut or post-surgical procedure with stiches (11%) or without stiches (43%) or burn scar/rash (46%) and (iii) presenting small or medium size scar (<4 cm).
The study was conducted following the tenets of the Declaration of Helsinki and OECD Good Laboratory Practices (GLP). The exper-

| Study protocol
All volunteers applied the same product the composition of which is based on a mix of vegetable waxes and bio-ceramides to reinforce, repair, regenerate, and soothe the skin. Subjects were asked to apply the product twice a day on their scar for 2 months and came to our facility at D 0 (baseline prior application), at one month (D 28 ) and two months (D 56 ), post application.
After checking the inclusion criteria at D 0 , during each visit, the local dermatologist (EJ) took acquisition of pictures of the scar, using the SkinCam® device. The dermatologist directly analyzed the volunteer's skin and scars through several parameters such as thickness, contrast, pigmentation, and vascularity. The scoring scale comprised 10 points (from 1 to 10 with no decimals) based on a mix of POSAS and VSS scales 5,6,10,13,14 focusing on few parameters as thickness, vascularity, contrast of the scars. In parallel, after one and two months, the volunteers answered to a short self-assessment questionnaire with five points agreement scale (agree; somewhat agree; nor agree, nor disagree; somewhat disagree; disagree), with the following items: "Skin feels smoother in the area surrounding the scar," "The cream helps restore the homogeneity of my scar," "Scar surface is smoother." "My scar is less red," "Color difference between my scar and the rest of my skin is less noticeable." Answers "Agree and Somewhat agree" questions were pooled to obtain a gross and qualitative assessment of subjects, keeping in mind that the rather small size of the subjects' cohort (N = 37) does cannot afford a high statistical relevance but, more simply, aimed at assessing agreement or disagreement between objective and subjective data.

| SkinCam®: acquisition and Analysis
Acquisition with the SkinCam® device 15 ( Figure 1) is a nomadic camera that enables acquisition of images under several polarizations with 12 white LEDS light regularly spaced around the acquisition area. In this study, crossed polarization (C.P), and 3D reconstruction were used. It enables to follow-up the skin to a region of 2.5 cm in diameter at the laboratory by the dermatologist at D 0 , after 4 and 8 weeks of topical application.
A fully analyzed area for which a region of interest is automatically defined on each subject and each area at D 0 . The region of interest is automatically replaced at other time point thanks to a spatial registration algorithm. This fully analyzed area has been used to evaluate the appearance of the scars and the adjacent area over time ( Figure 2).
A segmented analysis area of the detected scar for which markers for both scar and healthy skin are first manually defined to initialize the algorithm. These markers are defined for each scar at baseline and automatically replaced at other time points thanks to a spatial registration algorithm. Then, thanks to the defined markers, the rest of the image is automatically segmented, allowing to measure the changes in color and the relief of the scar over time (Figure 3).

| Contrast
The contrast is a measurement of local variations. It is computed from the co-occurrence matrix and is defined as follows: where P i,j is the value of the co-occurrence matrix located in row I and column j, N the number of rows or columns of the co-occurrence matrix. A decrease in contrast results in a decrease in the visual smoothness of the texture.

| Entropy
The entropy is a measurement of randomness of the distribution intensity. It is computed from the co-occurrence matrix and is defined as follows: where P i,j is the value of the co-occurrence matrix located in row i and column j, and N is the number of rows or columns of the co-occurrence matrix.
The analysis of the skin texture parameters was performed on all area. For morphological parameters, the scar is segmented at each timepoint, and the segmentation is applied on the 3D image ( Figure 5). The area is defined as the number of pixels in the segmentation. Since segmentation is based on the contrast of color

F I G U R E 4 Lab color Space CIE.
p-value is >0.05, a time effect on the parameter is likely leading to compare the times in pairs by a Tukey method. Comparisons that give p-value<0.05 indicate that the variation of parameters between the two compared times is significant.

| Non-parametric tests
The Friedman test as used, as a non-parametric alternative to the ANOVA of two-way on samples when the hypothesis of normality and homogeneity of variance are not validated indicating that paired samples come from the same or similar population. If the Friedman test provides a p-value<0.05, a time effect impacts the parameter.
It is then possible to compare the time pairs by a Nemenyi method.
Comparisons which give p-value<0.05 indicates that the variation of parameters between the two compared times is significant.
Student t-test was used to analyze dermatologist's assessment.
All statistical calculations used XLstat supplied by Addinsoft™. After 28 and 56 days, the results show a combined improvement of the visual skin homogeneity (contrast) and skin texture regularity (entropy) between the scar and the adjacent area.

| Morphological parameters
The changes of scars' morphological parameters (area, depth, volume) after 28 days and 56 days are given in Figure 9. After 56 days, a statistically significant decrease in the detected scars and their depth is observed, showing that the scars decrease in size and relief.
After 28 and 56 days, the detected scars volume showed a statistically significant decrease. The representation of the mean case for each type of images are presented in Figure 10.
Globally the results of the Skincam® are summarized in Table 1.

| Coherence with patients" perception
From 4 weeks of use (and after), all women agree on an improvement of the skin on the following the asked criteria: "Skin feels smoother in the area surrounding the scar," "The cream helps restore the homogeneity of my scar," "Scar surface is smoother" and also on colorimetric parameters "my scar is less red," "color difference between my scar and the rest of my skin is less noticeable." Answers of patients are gathered in Table 2.
A summary of the inter-coherence between the 3 types of assessments is illustrated in Table 3.

| DISCUSS ION
The present study demonstrates the capacity and the added value of the SkinCam® Device in following various changes occurring during the scaring process. This device allows to take qualitative and standardized pictures of scars, that comprise 2D and 3D surface imaging technologies, that can easily quantify color and morphological parameters. Beyond a use for a characterization, the SkinCam® appears sufficiently accurate for monitoring the natural modifications of scars or the benefit of the application of cosmetic products on scars and to identify significant differences. To our knowledge, the use of the Skincam® device vis à vis scar modifications is a newly opened topic and attempts to compare our own data with published works of a comparable protocol failed.
The use of this device presents however some limitations such as (i) limited scar size (<2.5 cm) due to the acquisition field, (ii) scar located in a relatively flat area, and (iii) adopting the right pressure of the device onto the skin to best eliminate external light during the acquisition phase. Inversely, a too strong pressure might deform the skin surface, thereby altering the quality of the 3D images.
Whatsoever, the learning phase to correctly position the device was rapidly acquired in the present study.
Nevertheless, the deployment of this device by healthcare professionals as dermatologists, surgeons, or plastic surgeons to easily capture the scars or post-procedure impacts can be envisaged. It could complete their expertise, illustrate results, follow the visibility of the scars with scientific and technical images to help discussion with patients. In addition, we observe a good coherence among device's assessments and clinical observations as well as patients' perceptions.
As nomad device, it allows a usage outside laboratories or consulting rooms contrary to some existing methods. [17][18][19] The relevance TA B L E 2 Self-assessment questionnaire and associated changes at D 28 and D 56 after one-month regimen expressed by the 37 patients. Beyond scars, extending its use to monitor dynamic pathologies such as acne, 24 to follow its severity and a possible identification of lesions (including scarring acne) is a promising approach to follow and adjust treatment between visits. Such aspect is currently in progress and its findings will be the object of a future paper.

Questions/answers
To summary, this preliminary pilot study shows that the use of the SkinCam® device in the follow-up of some specific scars seems a promising additional tool to the eyes and knowledges of medical experts, that rapidly provide objective and easy to transfer data. EJ has received honorarium from Eurosyn.

DATA AVA I L A B I L I T Y S TAT E M E N T
No data shared due to commercial reasons.

E TH I C A L A PPROVA L
Authors declare human ethics approval was not needed for this study.