Safety and Efficacy of High-Intensity Macrofocused Ultrasound for Solar Lentigo in Chinese Population

Primary outcomes

1. Lab* Values of Lesional Area Using Dermoscopy and ImageJ

   Time frame: week0, week2, week4, week6 and week8

   Before treatment, one point on each side of every patient was selected for measurement. Follow-up measurements were taken at the same locations after treatment, and comparisons were made between the pre- and post-treatment values on the same side. This outcome measure involves the assessment of lesional areas in dermoscopy images, with the Lab* conversion of pigmentation intensity performed using ImageJ software. L* represents the lightness (brightness) of the lesion, where higher L* values indicate lighter lesions (improvement), ranging from 0 to 100. a* and b* represent the chromatic components (red-green and yellow-blue), both ranging from -128 to +127. Lower values in these components indicate lighter pigmentation, while higher values suggest darker lesions.

2. Physician Global Aesthetic Improvement Scale Score

   Time frame: week2, week4, week6 and week8

   Two physicians independently assessed the overall unilateral condition of each patient at various follow-up time points after treatment, comparing the numerical values obtained after treatment for the same side. Both scores were averaged as the final data. The Physician Global Aesthetic Improvement Scale (PGAIS) is a 5-point scale used to rate the global aesthetic improvement in appearance compared to pretreatment, as judged by the investigator. The scale ranges from -1 (worsening) to 3 (very much improved). The higher score indicates the better improving effect.

3. Subjective Global Aesthetic Improvement Scale Score

   Time frame: week2, week4, week6 and week8

   At each follow-up time point after treatment, patients self-evaluated their unilateral overall condition and compared the numerical values of the same side before and after treatment. This process was repeated at every follow-up time point. The Subjective Global Aesthetic Improvement Scale (SGAIS) is a 5-point scale used to rate the global aesthetic improvement in appearance compared to pretreatment, as judged by the patients. The scale ranges from -1 (worsening) to 3 (very much improved). The higher score indicates the better improving effect.

4. Transepidermal Water Loss (TEWL) Measurement of Lesional Area

   Time frame: week0, week2, week4, week6 and week8

   Before treatment, one point on each side of every patient was selected for measurement. Follow-up measurements were taken at the same locations after treatment, and comparisons were made between the pre- and post-treatment values on the same side. Transepidermal Water Loss (TEWL) TEWL can be used to assess a patient's skin barrier function, with lower values indicating stronger barrier function.

   This outcome measure involves the assessment of Transepidermal Water Loss (TEWL), which quantifies the amount of water evaporating through the skin. TEWL is a key indicator of skin barrier function and hydration levels. In this study, TEWL was measured using Tewameter Hex (Courage Khazaka Electronic GmbH) that records the rate of water loss through the skin in g/m²/h (grams per square meter per hour). Lower TEWL values (less water loss) suggest an improved skin barrier, which is typically the result of effective treatment and increased skin hydration.

5. Skin Elasticity Measurement of Lesional Area

   Time frame: week0, week2, week4, week6 and week8

   Before treatment, one point on each side of every patient was selected for measurement. Follow-up measurements were taken at the same locations after treatment, and comparisons were made between the pre- and post-treatment values on the same side. Skin elasticity was assessed using Cutometer Dual MPA580 (Courage Khazaka Electronic GmbH, Köln, Germany), which measures the skin's resistance to deformation and recovery after deformation. The R-value represents the ratio of skin's ability to resist deformation (stiffness) and its ability to return to its original shape (elasticity). Higher R-values (greater elasticity) suggest that the skin is more resilient and can return to its original shape after deformation, indicating healthy skin with good elasticity and tone.