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

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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>θ</mml:mi></mml:mrow> </mml:semantics> </mml:math> ) dependence of SAW velocity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msub><mml:mi>C</mml:mi> <mml:mi>R</mml:mi></mml:msub> </mml:mrow> </mml:semantics> </mml:math> ) relative to fiber orientation. Validation experiments were conducted on chicken thighs and human forearms. In chicken thighs, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msub><mml:mi>C</mml:mi> <mml:mi>R</mml:mi></mml:msub> </mml:mrow> </mml:semantics> </mml:math> showed significant differences across propagation directions ranging from 90° to 0° ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>p</mml:mi></mml:mrow> </mml:semantics> </mml:math> = 0.008 < 0.05). In the dermis layer of forearms, the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msub><mml:mi>C</mml:mi> <mml:mi>R</mml:mi></mml:msub> </mml:mrow> </mml:semantics> </mml:math> demonstrated significant angular dependence ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>p</mml:mi></mml:mrow> </mml:semantics> </mml:math> = 0.031), with a percentage change of 31% while Young's modulus ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>E</mml:mi></mml:mrow> </mml:semantics> </mml:math> ) 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.