Quantitative Assessment of Human Anisotropic Skin Elasticity Using the Dispersion Curve of Surface Acoustic Wave...

Accurate assessment of skin elasticity is critical for understanding its physiological and pathological conditions. Conventional models often neglect anisotropy, leading to inconsistent measurements. We investigated skin anisotropic using Surface acoustic wave (SAW) based Optical Coherence Elastography (OCE), analyzing the angular ( $\theta$ ) dependence of SAW velocity ( $C_R$ ) relative to fiber orientation. Validation experiments were conducted on chicken thighs and human forearms. In chicken thighs, $C_R$ showed significant differences across propagation directions ranging from 90° to 0° ( $p$ = 0.008 < 0.05). In the dermis layer of forearms, the $C_R$ demonstrated significant angular dependence ( $p$ = 0.031), with a percentage change of 31% while Young's modulus ( $E$ ) increased by 21.7 ± 11.5 kPa (60.32%) from 90° to 0°. No significant dependence was found in the hypodermis layer. These results demonstrate that incorporating anisotropy improves elasticity estimation and provides a practical foundation for skin assessment.