Institute of Biomechanics and Medical Engineering, AML, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, PR China.
Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, PR China.
J Biomech. 2024 Sep;174:112279. doi: 10.1016/j.jbiomech.2024.112279. Epub 2024 Aug 10.
In vivo mechanical characterization of skin finds broad applications in understanding skin aging, diagnosis of some skin diseases and assessing the effectiveness of diverse skin care strategies. Skin has a layered structure consisting of the epidermis, dermis and subcutaneous layers. Although much effort has been made towards mechanical characterization of skin, it remains a challenging issue to measure the mechanical properties of an individual layer in vivo. To address this issue, we here report a guided wave elastography method for layered human skin which incorporates the effect of muscle states. Both finite element simulations and phantom experiments have been performed to validate the method. For skin-mimicking phantoms with different fat layer thicknesses, the errors in the identified shear modulus of the skin layers are no more than 11 %. In vivo experiments have been carried out on 6 healthy subjects to demonstrate the potential use of the method in clinics. A statistical analysis indicates the muscle contraction contributes to the stiffening of the skin (p < 0.001). Finally, a phase diagram has been constructed to reveal the extent to which muscle sates (including both passive and active states) affect the measurement of elastic modulus of a skin layer, which may guide the application of the method in practice.
体内皮肤力学特性分析在研究皮肤老化、某些皮肤疾病诊断以及评估各种皮肤护理策略的有效性方面具有广泛的应用。皮肤具有分层结构，包括表皮、真皮和皮下组织。尽管已经进行了大量的皮肤力学特性分析研究，但在体内测量单个皮肤层的力学特性仍然是一个具有挑战性的问题。为了解决这个问题，我们在这里报告了一种针对分层人体皮肤的导波弹性成像方法，该方法考虑了肌肉状态的影响。我们进行了有限元模拟和体模实验来验证该方法。对于具有不同脂肪层厚度的皮肤模拟体模，所识别的皮肤层剪切弹性模量的误差不超过 11%。我们对 6 名健康受试者进行了体内实验，以证明该方法在临床上的潜在用途。统计分析表明，肌肉收缩会导致皮肤变硬（p<0.001）。最后，构建了一个相位图来揭示肌肉状态（包括被动和主动状态）对皮肤层弹性模量测量的影响程度，这可能有助于该方法在实际中的应用。
