Résumé
Objective To investigate imaging characteristics of human skin in different sites by using 20-MHz and 50-MHz high-frequency ultrasonography,and to compare the reliability of skin thickness measurement by the above two approaches of ultrasonography.Methods A total of 39 healthy volunteers aged 18-39 years were enrolled into this study.Then,20-MHz and 50-MHz ultrasonography were separately performed to image 20 different sites on the body,and the thickness of the epidermis and dermis were measured and evaluated by 3 dermatologists independently.The ultrasonic images were analyzed,and the intraclass correlation coefficient (ICC) was used to assess and compare the reliability of skin thickness measurement by 20-MHz and 50-MHz ultrasound.Results The ICC values were less than or close to 0.7 in epidermal thickness measurement at almost all the tested sites between 20-MHz and 50-MHz ultrasonography,suggesting poor reliability.However,20-MHz and 50-MHz ultrasonography showed excellent reliability in dermal thickness measurement with the ICC greater than 0.75 at almost all the tested smooth and flat body sites.The 20-MHz ultrasound could provide clear images of the dermis and subcutaneous tissue,while 50-MHz ultrasound could only provide clearer images of the dermis in details.In some uneven sites with complex anatomical structures,20-MHz and 50-MHz ultrasound probes had their own advantages and disadvantages in imaging depth and detail resolution.Conclusions The 20-MHz and 50-MHz ultrasono-graphy both can serve as non-invasive imaging techniques to show structures of the epidermis and dermis better.In different parts of human body,ultrasound frequencies should be selected according to their imaging characteristics.