Regnault Gabriel, Wang Ruikang K, O'Donnell Matthew, Pelivanov Ivan
Univ Lyon, Université Claude Bernard Lyon 1, Centre Léon Bérard, INSERM, UMR, LabTAU, Lyon, France.
University of Washington, Department of Bioengineering, Seattle, Washington, United States.
J Biomed Opt. 2025 Dec;30(12):124503. doi: 10.1117/1.JBO.30.12.124503. Epub 2025 Aug 5.
Dynamic optical coherence elastography can excite and detect propagating mechanical waves in soft tissue without physical contact and in near real time. However, most soft tissue is anisotropic, characterized by at least three independent elastic moduli. As a result, reconstructing these moduli from mechanical wave fields requires a complex procedure.
We consider a nearly incompressible transverse isotropic (NITI) material, which has been shown to locally define the symmetry of many soft tissues such as muscle, tendon, skin, cornea, heart, and brain. Reconstruction of elastic moduli in the NITI medium using Rayleigh waves is addressed here. A method to accurately compute the angular dependence of Rayleigh wave phase velocity for the most common geometries (point-like and line sources) of mechanical wave excitation is described.
When a line source is used to launch plane mechanical waves over the medium surface, the phase velocity of Rayleigh waves in the direction of propagation is directly accessible. For a point-like source, propagation of the energy flux is tracked (i.e., its group velocity), which cannot be directly used for moduli inversion. In this case, angular spectrum decomposition is used to access the phase velocity. Both numerical simulations in OnScale and experiments in a stretched PVA phantom were performed.
We show that both methods (line source wave excitation and angular decomposition from a point-like source) produce similar results and accurately estimate the angular anisotropy of the Rayleigh wave phase velocity. We also explicitly show that a commonly used group velocity approach leads to inadequate moduli inversion and should not be used for reconstruction.
We suggest that the line source is best when a surface area must be scanned, whereas the point-like source with the proposed phase velocity reconstruction is best for single-point moduli estimation or when tissue motion is a concern.
动态光学相干弹性成像能够在不进行物理接触的情况下近乎实时地激发并检测软组织中传播的机械波。然而，大多数软组织是各向异性的，其特征是至少具有三个独立的弹性模量。因此，从机械波场重建这些模量需要一个复杂的过程。
我们考虑一种近不可压缩横向各向同性（NITI）材料，已证明它能局部定义许多软组织（如肌肉、肌腱、皮肤、角膜、心脏和大脑）的对称性。本文探讨了使用瑞利波重建NITI介质中的弹性模量。描述了一种精确计算机械波激发的最常见几何形状（点状和线状源）下瑞利波相速度角度依赖性的方法。
当使用线状源在介质表面发射平面机械波时，瑞利波在传播方向上相速度可直接获取。对于点状源，追踪能量通量的传播（即其群速度），但群速度不能直接用于模量反演。在这种情况下，使用角谱分解来获取相速度。进行了OnScale中的数值模拟和拉伸PVA模型实验。
我们表明两种方法（线状源波激发和点状源的角分解）产生相似结果，并准确估计了瑞利波相速度的角度各向异性。我们还明确表明，常用的群速度方法导致模量反演不足，不应将其用于重建。
我们建议，当必须扫描一个表面积时，线状源最佳；而对于单点模量估计或当关注组织运动时，具有所提出相速度重建方法的点状源最佳。
