Materials
SKIN, SKIN CONDITION, BLIND
The female facial skin image data were collected during a prospective, randomized, controlled, single-center clinical trial designed to compare the skin condition before and after TCA intervention in two parallel groups of women receiving TCA chemical peeling or placebo. The procedure was applied to women at the age of 59–65, whose eligibility to participate was assessed by the aesthetic medicine doctor against the following criteria: Fitzpatrick skin type II–III, no contraindications for chemical exfoliation, no previous treatments of TCA chemical peels and no previous exfoliating and rejuvenating treatments within six months. The inclusion and exclusion criteria are summarized in Table Participants inclusion and exclusion criteria.
Summary of patient groups and treatment steps.To blind the peel procedure, the personnel performing the procedure, data collectors, and data analysts did not know what substance was used, and the application procedure was the same in both the considered groups (per the TCA manufacturer recommendations). It includes make-up removal and cleansing of the skin, protecting sensitive areas with petroleum jelly, and applying the proper substances. Three layers of TCA (in the experimental group) and ultrasound gel (in the control group) were applied, with water rinsing in-between. After the last layer, the peeling/gel was washed off with water, and a cream with sunscreen SPF 50+ was applied. The application was carried out in four treatments every seven days. All the participants used soothing and moisturizing cream with SPF 50+ in daily care and up to three months after therapy. The novel TCA chemical peel (PQ Age Evolution®, Promoitalia, Italy) consists of: (1) Trichloroacetic acid The measurements were performed four times: at baseline—before the intervention, immediately after the last intervention, and one and three months post the last intervention. Patient groups with corresponding treatment procedures are summarized in Figure The required number of participants was evaluated based on the results of a pilot study, where five women were administered acid and five placebo. The assumptions for 2-way RM-ANOVA were met. Therefore the sample size was estimated using an eta-squared of the effect of hydration (measured using Multi Skin Test Center® MC750 B2, with the Corneometer® CM825 probe) for the between-factor analysis (eta-squared = 0.18). Setting alpha = 0.05, test power = 0.9, number of measurements = 6, number of groups = 2, correlation among repeated measures = 0.53, and eta-squared = 0.15, the total number of participants was 40 (at least 20 people in each group). Due to possible unpredictable and unavoidable factors, potentially reducing the group size, 23 people were qualified for each group, making the total sample size equal to 46. During the experiments, three participants were excluded from the analysis due to the absence or sunbathing, which is treated as possibly influencing the results. Consequently, the analysis was performed on 43 participants: 22 in the experimental group and 21 in the placebo group. The sample size agrees with the sizes described in the literature in similar experimentsThe HFUS images were acquired using DUB SkinScanner75 (tpm, taberna pro medicum GmbH, Germany) with a 24 MHz (B-mode frequency, 8 mm depth, and acoustic intensity level 40 dB) transducer in three locations on the patient’s face. The locations and ultrasound probe movement directions are visualized in Figure Left: facial model with superimposed image acquisition areas: the arrows indicate HFUS probe movement; Right: exemplary HFUS skin areas with segmented ROI for parameters estimation: blue - entry echo layer, green − 0.1 [mm] of upper epidermis, red − 0.2 [mm] ROI below the entry echo layer.