20MHz与50MHz超声皮肤成像与测量的比较研究

A comparison of 20-MHz and 50-MHz ultrasonography in imaging and measuring the skin

目的 了解20 MHz和50 MHz两种超声频率下人体不同部位皮肤的成像特点，比较两种频率超声测量皮肤厚度时的信度。方法 招募健康志愿者39名，年龄18 ~ 39岁。采用20 MHz和50 MHz超声对受试者全身20个部位皮肤进行超声成像，由3名医师分别测量各人体部位表皮与真皮的厚度，分析超声图像，并通过计算组内相关系数判断不同频率超声测量不同部位皮肤厚度时的信度。结果 两种频率超声测量各部位表皮时组内相关系数基本小于或接近0.7，信度不理想；在光滑平坦的人体部位，两种频率超声测量真皮时组内相关系数基本大于0.75，信度较高。20 MHz超声可以充分显示真皮与部分皮下组织，50 MHz超声仅能显示真皮层结构，但对细节成像更清晰。在一些解剖结构复杂且不平整的部位，两种频率超声在成像深浅、细节分辨能力方面各有利弊。结论 20 MHz和50 MHz超声作为无创影像工具能够很好地反映表皮及真皮结构；在人体不同部位，要根据两种频率超声的成像特点进行选择。

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 difibrent 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 uhrasono- graphy, 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.